Abstract
Multimorbidity in women with breast cancer may delay presentation, affect treatment decisions and outcomes. We described the multimorbidity profile of women with breast cancer, its determinants, associations with stage at diagnosis and treatments received. We collected self-reported data on five chronic conditions (hypertension, diabetes, cerebrovascular diseases, asthma/chronic obstructive pulmonary disease, tuberculosis), determined obesity using body mass index (BMI), and tested HIV status, in women newly diagnosed with breast cancer between January 2016 and April 2018 in 5 public hospitals in South Africa. We identified determinants of ≥2 of the 7 above mentioned conditions (defined as multimorbidity), multimorbidity itself with stage at diagnosis (advanced (III-IV) vs. early (0-II)) and multimorbidity with treatment modalities received. Among 2281 women, 1001 (44%) presented with multimorbidity. Obesity (52.8%), hypertension (41.3%), HIV (22.0%) and diabetes (13.7%) were the chronic conditions that occurred most frequently. Multimorbidity was more common with older age (OR=1.02; 95% CI 1.01–1.03) and higher household socioeconomic status (HSES) (OR=1.06; 95% CI 1.00–1.13). Multimorbidity was not associated with advanced stage breast cancer at diagnosis, but for self-reported hypertension there was less likelihood of being diagnosed with advanced stage disease in the adjusted model (OR 0.80; 95% CI 0.64–0.98). Multimorbidity was associated with first treatment received in those with early stage disease, p=0.003. The prevalence of multimorbidity is high among patients with breast cancer. Our findings suggest that multimorbidity had a significant impact on treatment received in those with early stage disease. There is need to understand the impact of multimorbidity on breast cancer outcomes.
Keywords: Breast cancer, chronic conditions, multimorbidity, stage at diagnosis and South African women
INTRODUCTION
Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer death in women worldwide, accounting for 6.6% of all cancer deaths.1 In South Africa, it is also the most common cancer among women, accounting for 20.8% of all female cancers. Age-standardized annual incidence rates are 18 per 100,000 in black women, 49 in women of mixed ancestral, 57 in the Asian women, and 88 in white South African women.2
The strongest determinant of breast cancer survival is stage at diagnosis3–5 and over 50% of women in South Africa have advanced stage disease at diagnosis.6 A similar situation exists across sub-Saharan Africa (SSA), attributable in part to modifiable factors which include lack of early diagnosis strategies at the primary care level,7 inadequate knowledge and awareness of breast cancer, inadequate access to care, socioeconomic factors,5, 6, 8 as well as tumour biology.9
In addition to late diagnosis, another challenge to breast cancer control in South Africa may be the presence of chronic conditions at the time of breast cancer diagnosis. Multimorbidity has been defined as the presence of two or more chronic conditions in the same individual.10 In South Africa, the effective treatment of infectious diseases, such as human immunodeficiency virus (HIV), has extended life expectancy, leading to increases in the prevalence of age-related chronic conditions. The number of people with two or more chronic conditions, such as cancer, hypertension, diabetes, obesity, HIV and tuberculosis is also growing rapidly and the burden is worse in poor communities.11 Patients with multimorbidity are at higher risk for inadequate disease management due to independent management of each disease within overburdened health systems, significant out of pocket costs and poor adherence for the patients who are likely to have to take more medications, adverse drug reactions, and potential drug-drug, drug-enzyme and drug-gene interactions affecting treatment efficacy.10, 12 Further, patients with multimorbidity may be at additional risk of sub-standard care due to a high possibility of obtaining conflicting advice on care and treatment.13, 14 The burden of multimorbidity, its determinants and impact on healthcare is well established in high income countries,15, 16 but there are few studies in low and middle income countries.17, 18 Many women with breast cancer have other chronic diseases at the time of their breast cancer diagnosis, and these conditions may affect the stage at diagnosis of breast cancer, treatment modality, and prognosis.19–22 It has been demonstrated that patients with cancer and other chronic diseases have reduced quality of life and survival.22–24
In our previous work describing the prevalence of multimorbid health conditions among 798 black South African women with and without breast cancer, although multimorbidity prevalence in cases was not higher than in the age-matched general population, the prevalence in cases were themselves high: 79.5% were overweight or obese, 59.2% were hypertensive, 46.6% had impaired fasting plasma glucose, 16.5% were HIV positive and 64.2% had ≥2 chronic conditions.25 Other South African studies reported that the prevalence of multimorbidity increases with age26 and is associated with higher household income.17
The prevalence and patterns of multimorbidity in a given cancer patient population have important implications for targeted patient-oriented prevention, diagnosis, treatment, disease control and improved outcome strategies.27 The aim of this study is four-fold: (i) to describe the prevalence and patterns of multimorbidity in women newly diagnosed with breast cancer in five public hospitals in South Africa; (ii) to determine socio-demographic factors associated with different chronic conditions; (iii) to determine the factors associated with multimorbidity; and (iv) to assess whether multimorbidity is associated with breast cancer stage at diagnosis and first treatment received.
METHODS
We used data from a cohort of women enrolled in the ongoing South African Breast Cancer and HIV Outcomes study (SABCHO) collected between January 2016 and April 2018.28 Five public hospital breast centres across Gauteng and KwaZulu-Natal provinces served as recruitment sites: Chris Hani Baragwanath Academic Hospital (Soweto hospital, Johannesburg), Charlotte Maxeke Johannesburg Academic Hospital (Central Johannesburg hospital), Addington Hospital and Inkosi Albert Luthuli Central Hospital in Durban (KwaZulu-Natal (KZN) Durban hospitals), Grey’s Hospital, Pietermaritzburg (KZN Pietermaritzburg hospital) and Ngwelezane Hospital (KZN rural hospital). The tertiary hospitals where all patients were enrolled on the study and received their treatments are located in city centres. The Central Johannesburg, KZN Durban hospitals and KZN Pietermaritzburg hospital all provide diagnostic services, surgery, chemotherapy, radiation therapy and endocrine treatments. The Soweto hospital, Johannesburg provides diagnostic, surgical and endocrine treatment services and patients have to travel to the Central Johannesburg hospital for chemotherapy and radiation treatments. The KZN rural hospital provides only diagnostic services, endocrine treatments and follow up surveillance of patients following surgical, chemotherapy and radiation therapy treatments at KZN Durban hospitals located more than 200km away. In the KwaZulu-Natal province most patients undergo diagnostic procedures in the district referral hospitals and surgery is performed either at district hospitals or at the tertiary hospital centres. Some Patients have to bare out of pocket transport costs to access their treatment while others travel using hospital transport. The women differ in education and socioeconomic status with the more rural communities accessing the KZN Pietermaritzburg and KZN rural hospitals generally less educated and more impoverished than urban communities” The patient referral demographics for each participating hospital are shown in table 1.
Table 1:
Characteristics of the hospital sites
| Soweto hospital, Johannesburg1 | Central Johannesburg hospital2 | KZN Durban hospitals3 | KZN Pietermaritzburg hospital4 | KZN rural hospital5 | |
|---|---|---|---|---|---|
| Location | Johannesburg (Gauteng province) | Johannesburg (Gauteng province) | Durban (KwaZulu-Natal Province) | Pietermaritz-burg (KwaZulu-Natal Province) | Empageni (KwaZulu-Natal Province) |
| Main population catchment area (N) | Soweto (3 million) | Johannesburg, East and Central (1.5 million) | Durban metropolitan, (3.5 million) | Western KwaZulu-Natal and distant rural communities (3.5 million), | Uthungulu, Umkhanyakude, Zululand (3 million) |
| Surgery | Surgery performed at this hospital | Surgery performed at this hospital | Surgery performed at this hospital and in secondary hospitals | Surgery performed at this hospital and in secondary hospitals | Surgery performed at this hospital |
| Oncology capacity (Chemotherapy and radiotherapy) | None. Patients are referred to Central Johannesburg hospital | Full oncology capacity | Full oncology capacity | Full oncology capacity | None. Patients are referred to KZN Durban hospitals. |
Chris Hani Baragwanath Academic Hospital, Soweto Johannesburg
Charlotte Maxeke Johannesburg Academic Hospital
Addington Hospital and Inkosi Albert Luthuli Central Hospital, Durban, KwaZulu-Natal
Grey’s Hospital, Pietermaritzburg, KwaZulu-Natal
Ngwelezane Hospital, KwaZulu-Natal
This study was approved by the University of the Witwatersrand Human Research Ethics Committee (Approval Number: Ml50351, dated: 6th May 2015), and the Institutional Review Board of Columbia University (protocol number AAAQ1359, dated 1st January 2016). This study was performed in accordance with the Declaration of Helsinki.
Recruitment of participants
Women who were newly diagnosed with invasive breast cancer, were ≥18 years of age and had resided in South Africa for ≥ 5 years were eligible for enrolment in the SABCHO study. Patients who had a previous cancer diagnosis (excluding non-melanoma skin cancer or non-invasive cervical cancer), had previously received > 1 month of radiotherapy or chemotherapy, had previously received any endocrine therapy, or were unable to give informed consent, were excluded.
Study procedures
Women were enrolled on the day of the diagnostic visit following voluntary written informed consent. Participants consented to HIV testing. Those who tested positive were referred for ART initiation prior to commencement of cancer treatment. Those who refused HIV testing were still included in the study and HIV status was recorded as unknown.
Socio-demographic and anthropometric measures
Trained study staff collected detailed socio-demographic information (age, self-identified ethnicity, marital status, employment status, highest level of education completed, residential address); reproductive history (number of full term pregnancies, age at first full-term pregnancy, use of oral and injectable contraceptives, use of hormone replacement therapy) and behavioural factors (alcohol consumption, smoking). Tumour American Joint Committee on Cancer (7th edition) stage, grade, receptor status and first treatment received data were extracted from medical records.29 Participants were grouped by stage at diagnosis as early (I-II) or advanced (III-IV).
Household socio-economic scores were determined using self-reported home ownership, car ownership, possession of a washing machine or microwave, presence of a flush toilet inside the home and presence of indoor running water. We assigned a score of 1 for each of these items and the scores were added out of a total of six. We documented the residential address of each participant at enrolment and computed the shortest straight-line distance to the enrolling hospital in kilometres (km).
We assessed seven chronic conditions: obesity, hypertension, diabetes, cerebrovascular disease, asthma/COPD, HIV infection and tuberculosis. HIV status was tested using the enzyme-linked immunosorbent assay through the National Health Laboratory Services. Body weight and height measurements were measured at enrolment, and obesity was defined as a body mass index (BMI) ≥30.0 kg/m2. Patients were asked if they were ever treated for tuberculosis and whether they had ever been diagnosed and treated for the other four conditions (hypertension, diabetes, cerebrovascular disease and asthma/COPD). We defined multimorbidity as having ≥ 2 of these seven chronic conditions.
Data availability:
Data for this study contain confidential patient information. Data supporting the results reported in this article may be requested from the corresponding author.
Statistical analysis
Determinants of each chronic condition and multimorbidity (≥2 chronic conditions) were examined in a multisite pooled analysis using bivariate and multivariate logistic regression. Odds ratios (OR) for multimorbidity were examined in 3 models by adding potentially associated factors in a stepwise fashion. Model 1 we examined all socio-demographic factors (age, ethnicity, marital status, highest level of education, employment status and household socio-economic status). Model 2 included socio-demographic and geographical factors (hospital site and residential distance from the hospital), and model 3 included socio-demographic, geographical factors and behavioural factors (alcohol intake and smoking). Finally, multivariable logistic regression models were used to examine whether chronic conditions and multimorbidity were associated with advanced stage breast cancer (stage III-IV). We included in the multivariate models variables for which p-values were <0.1 in bivariate analysis with advanced stage breast cancer. ORs were examined in two models (model A (unadjusted) and model B (which was adjusted for age, race, highest level of education and hospital site). We further examined the associations between multimorbidity and first treatment received (primary surgery, neoadjuvant chemotherapy or neoadjuvant endocrine therapy) by their stage at diagnosis using Pearson’s Chi-squared test. Analysis was performed using Stata version 15 (StataCorp Ltd, Texas, USA).
RESULTS
A total of 2281 women were included in the study: 795 (34.9%) from Soweto, Johannesburg hospital, 511 (22.4%) from Central Johannesburg hospital, 435 (19.1%) from KZN Durban hospitals, 462 (20.2%) from KZN Pietermaritzburg hospital and 77 (3.4%) from KZN rural hospital (Table 2). The mean age at diagnosis was 56.2 ± 14.3 years; women from the two Johannesburg hospitals compared to the KZN cities hospitals (Durban and Pietermaritzburg) were significantly younger and more likely to be married. In the combined sample, the majority (76.9%) of women were black Africans while KZN Durban hospitals had the highest percentage of Asians (39.4%) compared to other sites, and central Johannesburg hospital had the highest number of white women (17.0%).
Table 2:
Socio-demographic characteristics, prevalence of chronic conditions and stage at breast cancer diagnosis in women newly diagnosed with breast cancer in South Africa, by study-site.
| Soweto, Johannesburg hospital (n=795) | Central Johannesburg hospital (n=511) | KZN Durban hospitals (n=436) | KZN Pietermaritzburg hospital n=462 | KZN rural hospital n=77 | Total N=2281 | P value | |
|---|---|---|---|---|---|---|---|
| Age in years, mean ± SD | 55.1 ± 14.3 | 55.3 ± 14.2 | 58.1 ± 13.6 | 57.3 ± 14.7 | 55.6 ± 14.8 | 56.2 ± 14.3 | 0.002 |
| Ethnicity | |||||||
| Asian | 7 (0.9%) | 18 (3.5%) | 172 (39.4%) | 63 (13.6%) | 1 (1.3%) | 261 (11.4%) | <0.001 |
| Black | 734 (92.3%) | 378 (74.0%) | 203 (46.6%) | 364 (78.8%) | 75 (97.4%) | 1,754 (76.9%) | |
| Mixed | 42 (5.3%) | 28 (5.5%) | 17 (3.9%) | 18 (3.9%) | 0 (0.0%) | 105 (4.6%) | |
| White | 12 (1.5%) | 87 (17.0%) | 44 (10.1%) | 17 (3.7%) | 1 (1.3%) | 161 (7.1%) | |
| Marital status | |||||||
| Married/co-habiting | 329 (41.5%) | 212 (41.5%) | 156 (36.1%) | 140 (30.5%) | 24 (31.2%) | 861 (37.9%) | 0.001 |
| Unmarried | 464 (58.5%) | 299 (58.5%) | 276 (63.9%) | 319 (69.5%) | 53 (68.8%) | 1,411(62.1%) | |
| Highest level of education | |||||||
| Completion of informal/primary education | 192 (24.2%) | 90 (17.8%) | 127 (29.7%) | 180 (39.2%) | 38 (52.1%) | 627 (27.7%) | <0.001 |
| Completion of high school/any tertiary education | 602 (75.8%) | 416 (82.2%) | 301 (70.3%) | 279 (60.8%) | 35 (47.9%) | 1,633 (72.3%) | |
| Employment status | |||||||
| Unemployed | 583 (73.3%) | 335 (65.6%) | 342 (78.4%) | 373 (80.7%) | 63 (81.8%) | 1,696 (74.4%) | <0.001 |
| Employed | 212 (26.7%) | 176 (34.4%) | 94 (21.6%) | 89 (19.3%) | 14 (18.2%) | 585 (25.6%) | |
| aHousehold socio-economic status (score 0–6), median(IQR) | 4(2–5) | 4(3–5) | 4 (2–4) | 2 (1–4) | 1 (1–2) | 2 (3–5) | <0.001 |
| Residential distance from hospital site (km), median (IQR) | 12.8 (6.8–27.2) | 19.7 (8.7–34.7) | 20.4 (16.056.1) | 84.1 (8.3–155.6) | 58.9 (29.1144.2) | 20.6 (8.9–42.9) | <0.001 |
| Have you ever consumed alcohol? | |||||||
| No | 616 (77.5%) | 407 (79.7%) | 359 (82.3%) | 382 (82.7%) | 68 (88.3%) | 1,832 (80.3%) | 0.039 |
| Yes | 179 (22.5%) | 104 (20.3%) | 77 (17.7%) | 80 (17.3%) | 9 (11.7%) | 449 (19.7%) | |
| Have you ever smoked? | |||||||
| No | 718 (90.3%) | 427 (83.6%) | 367 (84.2%) | 413 (89.4%) | 74 (96.1%) | 1,999 (87.6%) | <0.001* |
| Yes | 77 (9.7%) | 84 (16.4%) | 69 (15.8%) | 49 (10.6%) | 3 (3.9%) | 282 (12.4%) | |
| Stage at diagnosis | |||||||
| Early stage (0-II) | 402 (50.6%) | 196 (38.4%) | 172 (40.0%) | 181 (39.2%) | 14 (18.4%) | 965 (43.9%) | <0.001 |
| Advanced stage (III & IV) | 393 (49.4%) | 315 (61.6%) | 258 (60.0%) | 281 (60.8%) | 62 (81.6%) | 1309 (56.1%) | |
| Receptor subtype | |||||||
| Luminal A | 111 (14.1%) | 123 (24.6%) | 152 (35.0%) | 71 (15.4%) | 19 (24.7%) | 476 (21.1%) | <0.001 |
| Luminal B | 467 (59.5%) | 232 (46.4%) | 172 (39.7%) | 255 (55.3%) | 30 (38.9%) | 1156 (51.2%) | |
| HER2 enriched | 94 (12.0%) | 69 (13.8%) | 50 (11.5%) | 58 (12.6%) | 14 (18.2%) | 285 (12.6%) | |
| Triple negative | 113 (14.4%) | 76 (15.2%) | 60 (13.8%) | 77 (16.7%) | 14 (18.2%) | 340 (15.1%) | |
| Chronic conditions considered | |||||||
| Nutritional status (BMI) | |||||||
| aUnderweight & Normal (≤24.9 kg/m2) | 160 (21.8%) | 98 (20.6%) | 96 (23.4%) | 109 (24.4%) | 19 (24.7%) | 482 (22.5%) | 0.094 |
| Overweight (25–29.9 kg/m2) | 160 (21.8%) | 133 (28.0%) | 117 (28.5%) | 103 (23.1%) | 17 (22.1%) | 530 (24.7%) | |
| Obese (≥ 30.0 kg/m2) | 415 (56.4%) | 244 (51.4%) | 197 (48.1%) | 234 (52.5%) | 41 (53.2%) | 1,131 (52.8%) | |
| Self-reported hypertension | |||||||
| No | 487 (61.3%) | 322 (63.0%) | 224 (51.4%) | 254 (55.0%) | 51 (66.2%) | 1,338 (58.7%) | <0.001 |
| Yes | 308 (38.7%) | 189 (37.0%) | 212 (48.6%) | 208 (45.0%) | 26 (33.8%) | 943 (41.3%) | |
| HIV status | |||||||
| Negative | 564 (74.7%) | 401 (82.5%) | 342 (85.3%) | 343 (75.4%) | 45 (59.2%) | 1,695 (78.0%) | <0.001 |
| Positive | 191 (25.3%) | 85 (17.5%) | 59 (14.7%) | 112 (24.6%) | 31 (40.8%) | 478 (22.0%) | |
| Self-reported diabetes | |||||||
| No | 720 (90.6%) | 465 (91.0%) | 324 (74.3%) | 388 (84.0%) | 71 (92.2%) | 1,968 (86.3%) | <0.001 |
| Yes | 75 (9.4%) | 46 (9.0%) | 112 (25.7%) | 74 (16.0%) | 6 (7.8%) | 313 (13.7%) | |
| Self-reported prior tuberculosis | |||||||
| No | 742 (93.3%) | 491 (96.1%) | 394 (90.4%) | 417 (90.3%) | 70 (90.9%) | 2,114 (92.7%) | 0.002 |
| Yes | 53 (6.7%) | 20 (3.9%) | 42 (9.6%) | 45 (9.7%) | 7 (9.1%) | 167 (7.3%) | |
| Self-reported asthma/COPD | |||||||
| No | 763 (96.0%) | 482 (94.3%) | 399 (91.5%) | 444 (96.1%) | 71 (92.2%) | 2,159 (94.7%) | 0.007 |
| Yes | 32 (4.0%) | 29 (5.7%) | 37 (8.5%) | 18 (3.9%) | 6 (7.8%) | 122 (5.3%) | |
| Self-reported cerebrovascular disease | |||||||
| No | 773 (97.2%) | 503 (98.4%) | 412 (94.5%) | 453 (98.1%) | 74 (96.1%) | 2,215 (97.1%) | 0.005* |
| Yes | 22 (2.8%) | 8 (1.6%) | 24 (5.5%) | 9 (1.9%) | 3 (3.9%) | 66 (2.9%) |
HSES: Household socio-economic status (possessions) score determined from: (home ownership=1, motor vehicle=1, microwave=1, washing machine=1, flush toilet=1, indoor running water=1) Denominator= 6 (1 for Yes, 0 for No).
54 women were underweight
KZN (KwaZulu-Natal)
Missing values for covariates were as follows: marital status (n=9), highest level of education (n=21), BMI (n=138), HIV status unknown (n=108), stage at diagnosis (n=7).
P value* (Fisher’s exact test).
BMI (Body mass index), COPD (Chronic obstructive pulmonary disease)
SD (standard deviation), IQR (interquartile range), km (kilometres)
In the combined sample, most of the women had at least a high school education (72.3%), but there was a significant difference between the sites as 52.1% of women attending KZN rural hospital had only completed primary education. Overall >50% of women were unemployed; women from the Johannesburg hospitals and KZN Durban hospitals had higher HSES than women from KZN Pietermaritzburg and KZN rural hospitals. Participants from KZN Pietermaritzburg hospital had the furthest distance to travel and women from Soweto, Johannesburg hospital travelled the shortest distance (84.1 vs. 12.8km) (Table 2). There was a significant difference between the sites for smoking and alcohol consumption, with the KZN rural hospital reporting the least for both compared to the other sites. Overall, 56.1% of the women presented with advanced stage breast cancer. Soweto, Johannesburg hospital was the only site where more than half (50.6%) presented at an early (stage I-II). Most (72.3%) of the women had oestrogen and progesterone receptor positive (Luminal A and B) breast cancer (Table 2).
Prevalence of chronic conditions
At enrolment, 19.0% of the women reported no chronic conditions (hypertension, diabetes, cerebrovascular diseases, asthma/chronic obstructive pulmonary disease, tuberculosis, HIV and obesity) ranging from 10.4% in KZN rural hospital to 25.6% at Central Johannesburg hospital (Figure 1 and supplementary table 1). In the combined sample, 52.8% of women were obese. The second most common chronic condition was hypertension (41%), which ranged from 34% at the KZN rural hospital to 48.6% at KZN Durban hospitals. HIV was the third most prevalent chronic condition (22.0%) but with considerable variation, highest (40.8%) at the KZN rural hospital and lowest at the KZN Durban hospitals (14.7%). Diabetes ranked as the fourth most prevalent chronic condition affecting 14% of women, with <10% at the two Johannesburg hospitals. Finally ranking fifth, sixth and seventh were tuberculosis, COPD/asthma and cerebrovascular disease, respectively, with each present in less than 10% of breast cancer patients at each site. Overall, 43.9% of breast cancer patients met our definition of multimorbidity (presence of ≥2 additional chronic conditions) and KZN Durban hospitals had the highest proportion (51.6%) (Figure 1 and supplementary table 1).
Figure 1.

Percentage of women newly diagnosed with breast cancer from each hospital site in South Africa, with none, one, two or more of obesity, self-reported hypertension, self-reported diabetes, self-reported cerebrovascular disease, self-reported asthma/COPD, HIV and self-reported prior tuberculosis.
KZN (KwaZulu-Natal)
Bivariate and multivariable logistic regression models of associations between socio-demographic variables and each chronic condition are presented in supplementary table 3 and table 3 respectively. In the multivariate analysis, with every 1 year increase in age, there was an 8% increase in the odds of hypertension, 4% increase in the odds of having diabetes, 4% increase in the odds of cerebrovascular disease, 6% reduced odds of HIV and 3% reduced odds of tuberculosis. When compared to the black women, white women had reduced odds of all the chronic conditions except asthma and the Asian women had increased odds of hypertension, diabetes and asthma/COPD. Of the three measures of socio-economic status, HSES was most frequently associated with the presence of a chronic condition. Women with higher HSES were more likely to be obese, hypertensive, diabetic, report asthma/COPD, and were less likely to be living with HIV (Table 3). The variance in the different chronic conditions that could be explained by age, race and socio-economic status ranged from 2% for obesity to 22% for HIV infection.
Table 3:
Pooled multivariate logistic regression model of socio-demographic characteristics and association with chronic conditions in women newly diagnosed with breast cancer in South Africa.
| Socio-demographic characteristics | Obesity (BMI ≥ 30.0 kg/m2) | Hypertension | Diabetes | Cerebrovascular disease | Asthma/COPD | HIV positive | Tuberculosis |
|---|---|---|---|---|---|---|---|
| OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | OR (95% CI) | |
| Age in years | 1.00 (0.99–1.00) | 1.08 (1.07–1.09)b | 1.04 (1.03–1.05)b | 1.04 (1.02–1.06)b | 0.99 (.98–1.01) | 0.94 (0.93–0.95)b | 0.97 (0.95–0.98)b |
| Race | |||||||
| White | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) |
| Asian | 0.8 (0.6–1.3) | 3.3 (2.1–5.3)b | 9.4 (4.5–19.6)b | 1.1 (0.4–3.1) | 1.0 (0.5–2.1) | 0.3 (0.1–3.6) | 0.8 (0.2–3.0) |
| Black | 2.1 (1.4–2.9)b | 2.4 (1.6–3.5)b | 2.8 (1.4–5.8)b | 0.6 (0.2–1.6) | 0.5 (0.3–0.9) a | 16.4 (4.0–67.2)b | 2.5 (0.9–6.9) |
| Mixed | 1.5 (0.9–2.6) | 2.8 (1.6–5.0)b | 4.4 (1.9–10.3)b | 0.5 (0.1–2.8) | 0.7 (0.3–1.8) | 5.2 (1.1–25.7)a | 2.0 (0.5–7.2) |
| Highest level of education | |||||||
| Primary education and below | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) |
| Secondary and above | 1.2 (0.9–1.5) | 1.0 (0.8–1.2) | 0.9 (0.6–1.2) | 0.8 (0.4–1.4) | 0.8 (0.4–1.2) | 1.2 (0.9–1.6) | 0.7 (0.5–1.1) |
| Employment status | |||||||
| Unemployed | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) | 1.0 (Ref) |
| Employed | 1.2 (0.9–1.4) | 0.8 (0.6–1.0) | 0.7 (0.5–0.9)a | 0.7 (0.3–1.6) | 0.7 (0.4–1.2) | 1.2 (0.9–1.5) | 0.8 (0.6–1.2) |
| Household socio-economic status (score 0–6) | 1.2 (1.1–1.2)b | 1.1 (1.0–1.1) a | 1.1 (1.0–1.2) a | 0.9 (0.8–1.1) | 1.2 (1.0–1.3) a | 0.8 (0.8–0.9)b | 0.9 (0.8–1.0) |
| R2 | 0.02 | 0.19 | 0.11 | 0.06 | 0.02 | 0.22 | 0.04 |
OR (Odds ratio), 95% CI (95% confidence interval), COPD (Chronic obstructive pulmonary disease),
Significant at p<0.05,
Significant at p<0.001
HSES: Household socio-economic status (possessions) score determined from: (home ownership=1, motor vehicle=1, microwave=1, washing machine=1, flush toilet=1, indoor running water=1) Denominator= 6 (1 for Yes, 0 for No).
In table 4a, bivariate logistic regression showed positive associations between multimorbidity and age, marital status, hospital sites and negative associations with ethnicity, highest level of education, employment status, alcohol consumption and smoking. These significant associations at the bivariate level were further explored in multivariate logistic regressions in three models (Table 4b). In model 1 (socio-demographic variables only), age contributed independently to an increased odds of multimorbidity and being white was associated with a decreased odds of multimorbidity. In model 2 (socio-demographic and geographical factors) age and white ethnicity remained significant and being Asian was associated with a lower odds of multimorbidity. Women from KZN Durban hospitals (OR=1.90, 95% CI 1.43–2.53) and KZN Pietermaritzburg hospital (OR 1.49, 95% CI 1.13–1.98) had an increased odds of having multimorbidity and the factors in model 2 were able to explain 3.1% of the variance in multimorbidity. In model 3 (socio-demographic, geographical and behavioural variables), age, white and Asian ethnicity, enrolment at KZN Durban hospitals and KZN Pietermaritzburg hospital remained significant, although higher HSES was now associated with an increased odds of multimorbidity (OR=1.06, 95% CI 1.00–1.13), none of the behavioural factors were significant in the model (Table 4b).
Table 4a:
Pooled associations between socio-demographic, geographical and behavioural factors with chronic conditions (≥2 (multimorbidity) vs. <2) in women newly diagnosed with breast cancer.
| Characteristics | < 2 chronic conditions N=1280 | ≥2 chronic conditions (multimorbidity) N=1001 | Bivariate analysis OR (95% CI) | P value |
|---|---|---|---|---|
| Age in years, mean ± SD | 54.4 ± 15.0 | 58.4 ±13.0 | 1.02 (1.01–1.03) | <0.001* |
| Ethnicity (%) | ||||
| Black | 976 (76.2%) | 778 (77.7%) | 1.00 (Referent) | |
| Asian | 130 (10.2%) | 131 (13.1%) | 1.26 (0.97–1.64) | <0.001* |
| Mixed | 56 (4.4%) | 49 (4.9%) | 1.10 (0.74–1.63) | |
| White | 118 (9.2%) | 43 (4.3%) | 0.46 (0.32–0.66) | |
| Marital status (%) | ||||
| Married/co-habiting | 513 (40.2%) | 348 (34.9%) | 1.00 (Ref) | 0.010* |
| Unmarried | 763 (59.8%) | 648 (65.1%) | 1.25 (1.05–1.49) | |
| Highest level of education (%) | ||||
| Primary education and below | 324 (24.4%) | 303 (30.7%) | 1.00 (Referent) | 0.006* |
| Secondary education and above | 949 (74.6%) | 684 (69.3%) | 0.77 (0.64–0.93) | |
| Employment status (%) | ||||
| Unemployed | 921 (71.9%) | 775 (77.4%) | 1.00 (Referent) | 0.003* |
| Employed | 359 (28.1%) | 226 (22.6%) | 0.75 (0.62–0.91) | |
| Household socio-economic status (score 0–6), median (IQR) | 3(2–5) | 4(2–5) | 1.02 (0.97–1.07) | 0.488 |
| Hospital site (%) | ||||
| Soweto, Johannesburg | 472 (36.9%) | 323 (32.3%) | 1.00 (Referent) | <0.001* |
| Central Johannesburg | 318 (24.8%) | 193 (19.3%) | 0.89 (0.71–1.11) | |
| KZN Durban | 211 (16.5%) | 225 (22.5%) | 1.56 (1.23–1.97) | |
| KZN Pietermaritzburg | 240 (18.8%) | 222 (22.2%) | 1.35 (1.07–1.70) | |
| KZN rural | 39 (3.1%) | 38 (3.8%) | 1.42 (0.89–2.28) | |
| Residential distance from hospital site (km), median (IQR) | 19.9 (8.7–39.5) | 21.8 (9.1–48.1) | 1.00 (1.00–1.01) | 0.033* |
| Have you ever consumed alcohol? (%) | ||||
| No | 1004 (78.4%) | 828 (82.7%) | 1.00 (Ref) | 0.011* |
| Yes | 276 (21.6%) | 173 (17.3%) | 0.76 (0.62–0.94) | |
| Have you ever smoked? (%) | 0.044* | |||
| No | 1106 (86.4%) | 893 (89.2%) | 1.00 (Ref) | |
| Yes | 174 (13.6%) | 108 (10.8%) | 0.77 (0.60–0.99) |
OR (Odds ratio) = odds of reporting ≥2 chronic conditions compared with <2 chronic conditions,
variables significant at p<0.05.
HSES: Household socio-economic status (possessions) score determined from: (home ownership=1, motor vehicle=1, microwave=1, washing machine=1, flush toilet=1, indoor running water=1) Denominator= 6 (1 for Yes, 0 for No), KZN (KwaZulu-Natal), SD (standard deviation), IQR (interquartile range), km (kilometres)
Table 4b:
Pooled multiple logistic regression model of socio-demographic, geographical and behavioural factors associated with ≥2 chronic conditions (multimorbidity) in women newly diagnosed with breast cancer.
| Characteristics | Model 1 (Socio-demographic factors) OR (95% CI) | Model 2 (Socio-demographic and geographical factors) OR (95% CI) | Model 3 (Socio-demographic, geographical and behavioural factors) OR (95% CI) |
|---|---|---|---|
| Age in years | 1.02 (1.01–1.03)b | 1.02 (1.01–1.03)b | 1.02 (1.01–1.03)b |
| Ethnicity | |||
| Black | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| Asian | 1.05 (0.79–1.38) | 0.70 (0.50–0.97)a | 0.70 (0.50–0.97)a |
| Mixed | 0.99 (0.66–1.50) | 0.93 (0.61–1.40) | 0.97 (0.63–1.49) |
| White | 0.39 (0.27–0.58)b | 0.34 (0.23–0.51)b | 0.36 (0.24–0.54)b |
| Marital status | |||
| Married/co-habiting | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| Unmarried | 1.09 (0.90–1.30) | 1.06 (0.89–1.28) | 1.07 (0.89–1.29) |
| Highest level of education | |||
| Primary education and below | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| Secondary education and above | 1.04 (0.84–1.29) | 1.08 (0.87–1.35) | 1.08 (0.87–1.35) |
| Employment status | |||
| Unemployed | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| Employed | 0.93 (0.75–1.14) | 0.93 (0.75–1.15) | 0.93 (0.75–1.15) |
| Household socio-economic status (score 0–6) | 1.01 (0.96–1.07) | 1.06 (0.99–1.13) | 1.06 (1.00–1.13)b |
| Hospital site | |||
| Soweto, Johannesburg | 1.00 (Ref) | 1.00 (Ref) | |
| Central Johannesburg | 1.03 (0.81–1.31) | 1.02 (0.80–1.30) | |
| KZN Durban | 1.90 (1.43–2.53)b | 1.89 (1.42–2.51)b | |
| KZN Pietermaritzburg | 1.49 (1.13–1.98)a | 1.49 (1.12–1.97)a | |
| KZN rural | 1.57 (0.94–2.63) | 1.54 (0.92–2.57) | |
| Residential distance from hospital site (km) | 1.00 (0.99–1.00) | 1.00 (0.99–1.00) | |
| Have you ever consumed alcohol? | |||
| No | 1.00 (Ref) | ||
| Yes | 0.85 (0.67–1.07) | ||
| Have you ever smoked? | |||
| No | 1.00 (Ref) | ||
| Yes | 0.96 (0.71–1.29) | ||
| R2 | 0.028 | 0.031 | 0.033 |
OR (Odds ratio) = odds of reporting ≥2 chronic conditions compared with <2 chronic conditions
Significant at p<0.05,
Significant at p<0.001 KZN (KwaZulu-Natal)
Bivariate and multivariate logistic regression models of chronic conditions and multimorbidity associated with advanced stage breast cancer disease at diagnosis are presented in tables 5a and 5b respectively. In the bivariate analysis (Table 5a), obesity and hypertension were negatively associated with advanced stage breast cancer at diagnosis. Women who were HIV positive and women who reported prior tuberculosis had positive associations with advanced stage breast cancer at diagnosis. There was no significant association between multimorbidity and advanced stage breast cancer at diagnosis (OR=0.88, 95% CI 0.74–1.04) (Table 5a). The significant variables at p <0.1 were further explored in the multivariate model (Table 5b). In Model A, women who reported having hypertension had lower odds of advanced stage breast cancer and women who were HIV positive had higher odds of advanced stage breast cancer at diagnosis than those women without the disease. In model B, adjusting for age, race, highest level of education and hospital site, self-reported hypertension (OR=0.80, 95% CI 0.64–0.98) was the only chronic condition associated with advanced stage breast cancer disease (Table 5b).
Table 5a:
Pooled bivariate analyses of the association between chronic conditions and advanced stage disease amongst women newly diagnosed with breast cancer.
| Characteristics | Bivariate analysis OR (95% CI) | P value |
|---|---|---|
| Obese | 0.84 (0.70–0.99) | 0.041* |
| Self-reported hypertension | 0.74 (0.62–0.87) | <0.001* |
| Self-reported diabetes | 0.80 (0.63–1.01) | 0.064 |
| Self-reported cerebrovascular disease | 1.00 (0.61–1.64) | 0.998 |
| Self-reported asthma/COPD | 0.82 (0.57–1.18) | 0.286 |
| HIV positive | 1.52 (1.23–1.87) | <0.001* |
| Self-reported prior tuberculosis | 1.49 (1.07–2.08) | 0.019* |
| Multimorbidity | 0.88 (0.68–1.10) | 0.138 |
Significant at p<0.05, COPD (Chronic obstructive pulmonary disease)
Table 5b:
Pooled multivariate logistic regression models of chronic conditions associated with advanced stage disease (stages III-IV) in women newly diagnosed with breast cancer.
| Characteristics | Model A OR (95% CI) | P value | Model B OR (95% CI) | P value |
|---|---|---|---|---|
| Obese | 0.92 (0.77–1.09) | 0.340 | 0.85 (0.71–1.03) | 0.098 |
| Self-reported hypertension | 0.77 (0.64–0.92) | 0.005* | 0.80 (0.64–0.98) | 0.036* |
| HIV positive | 1.36 (1.09–1.71) | 0.008* | 1.07 (0.83–1.38) | 0.582 |
| Self-reported prior tuberculosis | 1.32 (0.93–1.88) | 0.123 | 1.22 (0.84–1.78) | 0.286 |
| R2 | 0.013 | 0.040 |
Significant at p<0.05, model A (unadjusted), model B (adjusted for age on presentation, race, highest level of education and hospital site)
In women with early stage (stages 0-II) breast cancer, there was a significantly higher proportion of women with multimorbidity who received neoadjuvant endocrine therapy (18.2%) compared to those without multimorbidity who received neoadjuvant endocrine treatment (10.5%), p=0.003 (Table 6).
Table 6:
Association between multimorbidity and first treatment received by stage at diagnosis in women newly diagnosed with breast cancer.
| Stages 0-II (Early stage) | Stages III & IV (Advanced stage) | |||||||
|---|---|---|---|---|---|---|---|---|
| Multimorbidity | Primary surgery | Neoadjuvant chemotherapy | Neoadjuvant endocrine therapy | P value | Primary surgery | Neoadjuvant chemotherapy | Neoadjuvant endocrine therapy | P value |
| N=662 (%) | N=141 (%) | N=131 (%) | N=125 (%) | N=881 (%) | N=206 (%) | |||
| No (< 2 chronic conditions) | 372 (73.7) | 80 (15.8) | 53 (10.5) | 0.003 | 67 (9.6) | 520 (74.7) | 109 (15.7) | 0.184 |
| Yes (≥ 2 chronic conditions) | 290 (67.6) | 61 (14.2) | 78 (18.2) | 58 (11.2) | 361 (70.0) | 97 (18.8) | ||
| *Total | 662 (70.9) | 141 (15.1) | 131 (14.0) | 125 (10.3) | 881 (72.7) | 206 (17.0) | ||
Total for stages 0-II (early stage) = 934, total for stages III & IV (advanced stage) = 1212. Some 135 women had missing treatment information. Row percentages shown
DISCUSSION
In this study, we found that among women newly diagnosed with breast cancer from 5 public hospitals across South Africa, more than 80% reported at least one chronic condition and 43.9% had two or more chronic conditions. Older women, higher HSES, and women enrolled at the KZN Durban and Pietermaritzburg hospitals, had higher odds of multimorbidity, while the Asian and white women were less likely to present with multimorbidity when compared to black women. Hypertensive women were less likely to have advanced stage breast cancer at diagnosis, whilst multimorbidity was not associated with advanced stage breast cancer at diagnosis.
The burden of multimorbidity in our cohort was high with 43.9% of the whole sample reporting two or more chronic conditions. Multimorbidity is of increasing concern in South Africa and this high prevalence of non-communicable and communicable multimorbidity has significant implications for the mode of health care delivery and the health system. Severe chronic conditions narrow treatment choices and are associated with poor quality of life and survival, especially in postmenopausal women.24, 30 In South Africa chronic disease management is meant to be delivered using the integrated chronic disease management approach;31 however this is yet to be achieved as people with multimorbidity receive fragmented and inefficient health care delivery.32, 33 There is a need for an effective integrated and comprehensive array of health services spanning from primary to tertiary levels.
The most common chronic condition reported in this sample of women with breast cancer was obesity (52.8%), which was much higher than report from the recent South African national survey with obesity prevalence of 41.7% in adult women (ranging from 30.6% among the white women to 49.2% among the Asian women).34
Our results indicate that multimorbidity in women with breast cancer is associated with socio-demographic characteristics (age, race and HSES) and hospital site where they are seeking health care. It is well accepted that multimorbidity is associated with increasing age, due to age-related chronic health conditions.35 The Asians in South Africa have been reported to have a high burden of chronic conditions,17 which is in keeping with our findings for individual chronic conditions in this population group. This is primarily the result of high prevalence of hypertension and diabetes in the Asian group; HIV prevalence was low. A study conducted among Asian South Africans living in Durban also reported a high burden of hypertension (47.5%), diabetes (20.1%), and obesity (32.4%).36 Despite this high finding of the prevalence of individual chronic conditions in Asian women in our cohort, they were still less likely to present with multimorbidity (OR=0.70, 95% CI 0.50–0.97) compared to the black African women. This may be due to the higher prevalence of obesity in the black women,37 and equally high burden of hypertension. South Africa has the highest burden of hypertension in people >50 years of age in SSA,27, 38 HIV-infection and tuberculosis were almost exclusive to the black African women in our cohort. This double burden of communicable and non-communicable diseases in women with breast cancer is of concern and can ultimately impact on treatment, quality of life and survival.
We found that women with higher HSES were more likely to present with multimorbidity, independent of ethnicity. There is a dearth of knowledge on the association between socioeconomic status and multimorbidity in South Africa; however our finding is in contrast to other South African studies that reported that poorer women and those socioeconomically deprived bear a greater burden of multimorbidity.39, 40 Women socioeconomically deprived had 50% increased odds of having multimorbidity compared to those not socioeconomically deprived.40 This may be due to different definitions and mode of measurement of socio-economic status in the studies.
Patients also experience varying delays within the referral network, as reflected in significant differences in the proportions of advanced stage (stages III & IV) at presentation of patients at the different sites (ranging from 50% (lowest) at the Soweto, Johannesburg hospital and 73% (highest) at the KZN Pietermaritzburg and KZN rural hospital. These challenges are compounded for patients with high multimorbidity who have to visit other clinics for their chronic medications apart for their breast cancer treatments.
Some of our findings on the association between individual chronic conditions, multimorbidity, and stage of breast cancer diagnosis are consistent with previous work in South Africa and SSA. Although obesity was associated with a reduced risk of being diagnosed with advanced stage breast cancer in the bivariate analysis, when included in the multivariable analysis with other chronic conditions this was no longer significant. This is in keeping with studies from Africa and high income countries41–43 where obesity did not emerge as being associated with advanced stage disease at breast cancer diagnosis. Obesity is a risk factor for luminal type breast cancers, which tend to be slower growing and less likely to be diagnosed at advanced stage.44, 45 Obesity is not a comorbidity that has been shown to increase contact with health services in our setting; we therefore cannot imply its protective effect from regular contact with the health facilities.
Women who reported being hypertensive were less likely to have advanced stage of breast cancer at diagnosis, before and after adjusting for potential covariates. This may imply regular contact with the health systems that may result in patient breast cancer education by the health services or a surveillance effect leading to earlier stage at diagnosis.19 This may also be related to tumour biology because breast cancer in younger women (with less hypertension prevalence) tend to be the more aggressive subtypes.46–48 HIV infection, prior tuberculosis, diabetes, asthma/COPD, cerebrovascular disease and multimorbidity was not associated with advanced stage breast cancer at diagnosis.
Our findings show that multimorbidity was significantly associated with first treatment received in women with early stage breast cancer. Among women with multimorbidity with early stage breast cancer, a large proportion were placed on less aggressive neoadjuvant endocrine therapy. Older women with multimorbidity are more likely to have poor Eastern Cooperative Oncology Group (ECOG) performance status and not able to withstand the stress of surgery or chemotherapy and are therefore not likely to be placed on standard more aggressive treatments.49
Some limitations need to be noted. As the data on the various chronic conditions was self-reported the prevalence of these conditions may be higher than reported. The list of chronic conditions was not comprehensive, and therefore certain health conditions may not have been detected and may result in potential confounding. We had to rely on patient self-reports of their diagnosed comorbidities and that they were on treatment. In South Africa hospital records are not electronically centralised and patient records from different clinics are not readily accessible for diagnostic and treatment details. Another limitation was that in the interview we did not specify if the patient had a current history of tuberculosis or previous history, whilst not ideal, it was not a common prior condition so did not affect overall results, as seen in supplementary table 2 where the tuberculosis rows and columns are all relatively small. Despite these limitations, the strength of this study include the uniquely large sample of South African women with breast cancer and inclusion of hospitals in different geographical regions. We described the burden and pattern of multimorbidity, and difference in chronic conditions between different hospital settings and have also measured factors associated with individual chronic conditions as well as multimorbidity. Further this study provides data on the association between these chronic conditions and multimorbidity, and advanced stage breast cancer at diagnosis, in South Africa women.
Our finding give important insight into demographic and socio-economic factors associated with multimorbidity in women with breast cancer in South Africa. There is need for policymakers to evaluate the effect of multimorbidity on the health system and its impact on the limited health care resources.
In conclusion, we have demonstrated a high prevalence of multimorbidity in women newly diagnosed with breast cancer from different public hospital settings in South Africa, with many of these chronic conditions being associated with socio-demographic factors. Women that were hypertensive were less likely to be diagnosed with advanced stage breast cancer. Our findings contribute to the literature in understanding socio-demographic factors associated with multimorbidity in South Africa. There is need to understand how multimorbidity may impact breast cancer outcomes.
Supplementary Material
Novelty and impact statement.
“Multimorbidity in women with breast cancer increases with age and may delay presentation, influence treatment decisions and outcome. This study shows that 44% of women newly diagnosed with breast cancer presented with multimorbidity, with obesity, hypertension, HIV and diabetes most prevalent. With effective treatment of HIV in South Africa leading to an increase in the prevalence of age related chronic conditions, there is a need to evaluate the effect of multimorbidity not only on patients but also on the health system, and its impact on the scarce health care resources”
Acknowledgement:
We are grateful to the patients who provided the data for this study and to the team at the breast unit of Chris Hani Baragwanath Academic Hospital, Charlotte Maxeke Johannesburg Academic Hospital, Addington Hospital and Inkosi Albert Luthuli Central Hospitals, Grey’s Hospital, Pietermaritzburg and Ngwelezane Hospital, who have served and continue to serve the patients with skill and devotion.
Funding:
This work was supported by NIH grant (NCI 1R01CA192627) http://grantome.com/grant/NIH/R01-CA192627-01 to Drs. Jacobson, Joffe, Neugut and Ruff; (ii) the South African Medical Research Council/University of the Witwatersrand Common Epithelial Cancer Research Centre (MRC/WITS CECRC) http://www.mrc.ac.za/epithelial/Epithelial.htm led by Dr Ruff; and (iii) the Cancer Association of South Africa (CANSA) grant “Down-staging and improving survival of breast cancer in South Africa” http://www.cansa.org.za/downstaging-and-improving-survival-of-breast-cancerin-sa-dr-herbert-cubasch(Dr Cubasch) ; (iv) a Conquer Cancer Foundation of the American Society of Clinical Oncology 2018 Young Investigator Award to Dr. O’Neil; (v) Lisa K. Micklesfield is supported by the South African Medical Research Council and (vi) Shane A. Norris is supported by the DST-NRF Centre of Excellence in Human Development at the University of the Witwatersrand, Johannesburg, South Africa.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The Wits Health Consortium (PTY) Ltd provided support in the form of payroll administration of salaries from grant funds for authors OA, MJ, SAN, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.
List of abbreviations
- BMI
body mass index
- HIV
human immunodeficiency virus
- HSES
household socio-economic status
- KZN
KwaZulu-Natal
- OR
odds ratio
- CI
confidence interval
- SD
standard deviation
- IQR
interquartile range
- SSA
sub-Saharan Africa
- SABCHO
South African Breast Cancer and HIV Outcomes study
- COPD
Chronic obstructive pulmonary disease
- CVD
cerebrovascular disease
Footnotes
Informed consent: All participants provided written informed consent
Conflict of Interest:
Dr. O’Neil declares personal fees from Ipsen outside the submitted work. Dr. Neugut receives consultant fees from Otsuka Pharmaceuticals, United Biosource Corp, Hospira, and Eisai and serves on the scientific advisory board of EHE International. All other authors declare no conflict of interest.
Publisher's Disclaimer: Disclaimer: Where authors are identified as personnel of the International Agency for Research on Cancer / World Health Organization, the authors alone are responsible for the views expressed in this article and they do not necessarily represent the decisions, policy or views of the International Agency for Research on Cancer / World Health Organization.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
Data for this study contain confidential patient information. Data supporting the results reported in this article may be requested from the corresponding author.
