Abstract
Background:
Females 80 years and older comprise 22% of the total U.S. survivor population, yet the impact of cancer on the physical well-being of women is this age group has not been well characterized.
Methods:
We compared women, 80 years of age and older in the Women’s Health Initiative extension 2, who did ( n = 2,270) and did not ( n = 20,272) have an adjudicated history of cancer during Women’s Health Initiative enrollment; analyses focused on women >2-years postcancer diagnosis. The physical functioning subscale of the RAND-36 was the primary outcome. Demographic, health-status, and psychosocial covariates were drawn from Women’s Health Initiative assessments. Analysis of covariance was used to examine the effect of cancer history on physical function, with and without adjustment for covariates.
Results:
In adjusted models, women with a history of cancer reported significantly lower mean physical functioning (56.6, standard error [ SE ] 0.4) than those without a cancer history (58.0, SE 0.1), p = .002. In these models, younger current age, lower body mass index, increased physical activity, higher self-rated health, increased reported happiness, and the absence of noncancer comorbid conditions were all associated with higher physical functioning in both women with and without a history of cancer.
Conclusions:
Women older than 80 years of age with a cancer history have only a moderately lower level of physical function than comparably aged women without a cancer history. Factors associated with higher levels of physical functioning were similar in both groups.
Keywords: Cancer, Physical function, Comorbidities, Women, Survivor
It is estimated that there are 1.4 million U.S. women over the age of 80 with a history of cancer ( 1 ). Females 80 years and older comprise 22% of the total survivor population, and the proportion of survivors over 65 years is expected to increase 42% by 2020 and even more dramatically between 2020 and 2050 ( 1 ). Despite the large number of older female survivors, there is very little research characterizing the implications of cancer diagnosis and treatment on the physical and emotional well-being of these women.
Available evidence suggests that older cancer survivors report more limitations in physical functioning and greater disability than age-matched, noncancer controls ( 2–4 ). Cancer diagnosis and treatment, in general, across age groups is often associated with higher comorbidity burden and poorer self-rated health later in life ( 2 , 3 ). Risk factors for declines in physical health and functioning are varied, but include increased age, comorbid conditions, and physical performance limitations at the time of diagnosis ( 5 , 6 ). The trajectory of declines in self-rated health and function are not clear postdiagnosis, but may be most pronounced in the first few years after cancer diagnosis ( 4 , 7 , 8 ). In fact, recent studies of older cancer survivors suggest that physical limitations are more closely associated with presence of comorbidities than duration of survivorship ( 9 ). Further, Cohen and colleagues ( 10 ) suggest that the impact of cancer and its treatments may be attenuated over time and largely replaced by changes related to aging itself, although this has been debated ( 11 ).
Current evidence, however, is limited by under representation of survivors over age 80 (generally less than 20% of cancer survivors in studies were >80, when this was reported eg, 3 , 7 ) and a predominant focus on breast cancer survivors. In this age group, it is largely unknown how a prior diagnosis of cancer affects physical functioning and overall health in the context of other comorbid conditions associated with aging. As one of the largest U.S. cohort studies of older women, the Women’s Health Initiative (WHI) offers a unique opportunity to compare the health and physical functioning of older female cancer survivors to older women without a cancer history and to identify risk factors for physical functioning limitations after a cancer diagnosis. We are also able to add to the literature on physical functioning among older cancer survivors by examining the impact of psychosocial variables such depression and optimism, which have been found to be significant predictors of physical functioning and quality of life in prior studies of older adults with and without chronic medical conditions ( 12–14 ).
The aims of this analysis are: (a) to compare the health behaviors, psychosocial factors, comorbidities, and physical functioning of women 80 years and older with and without a history of cancer, and (b) to determine independent predictors of physical functioning in women ≥80 years of age and older, stratified by cancer history. We hypothesize that women aged ≥80 with a history of cancer will report poorer physical functioning than those women with no cancer history, even after controlling for demographics, health behaviors, health status, and psychological factors.
Methods
Study Population
The WHI is a large longitudinal study of 161,809 women recruited at 40 clinical centers across the United States from 1993 to 1998, with both an observational study and randomized clinical trials of estrogen plus progestin, estrogen alone, dietary modification, and calcium and vitamin D supplementation ( 15 , 16 ). Women were 50–79 years of age and postmenopausal at study entry. The composition of this cohort is described in detail earlier in this special issue (Beavers and colleagues). Briefly, women were selected for the 80+ cohort and this analysis if they were: (a) enrolled in one of the WHI clinical trials or the observational study cohort; (b) consented to the second WHI extension (2010–2015) ( 17 ); (c) were 80 years of age or older on the September 17, 2012 data release cutoff; and (d) had physical functioning data collected after turning 80 years of age.
Study Variables
Cancer history
Reports of any cancer diagnoses were elicited every 6 months. Cancers were then confirmed by medical record and pathology report review by trained physicians at each clinic and were centrally adjudicated by reviewers. Those women with a cancer diagnosis ( 18 ), excluding cases of nonmelanoma skin cancer, after their enrollment in the WHI were considered to be cancer survivors. We excluded women: (a) who reported a history of cancer at WHI baseline because of incomplete date of diagnosis and lack of independent confirmation; (b) with an unknown primary site or unknown cancers using the Surveillance, Epidemiology, and End Results coding system; (c) with distant or unknown cancer stages (according to Surveillance, Epidemiology, and End Results Summary Staging) at diagnosis; and (d) who completed their 80+ physical functioning assessment <24 months after date of any cancer diagnosis to minimize the short-term influence of cancer treatment on physical functioning. Cancer-related variables collected as part of the adjudication process included cancer type and date of cancer diagnosis (used to calculate time since most recent cancer diagnosis).
Primary outcome
The physical functioning subscale of the RAND 36-item health survey ( 19 , 20 ), administered at the most current assessment after turning 80, was used as the primary outcome. This subscale score is standardized to a mean of 50 and a standard deviation ( SD ) of 10; higher scores indicate better functioning. The RAND-36 has been used extensively in studies of older adults ( 21 ) and distinguishes between older adults with and without chronic disease, including different types of cancer ( 22 ).
Demographics and health-related variables
Information regarding race/ethnicity, educational attainment, and marital status was self-reported by women during their baseline WHI assessment. Date of birth was used to calculate current age at the time of the 80+ assessment. Data obtained from the most recent participant assessments after cancer diagnosis were used for: self-reported health (categorized as excellent/very good/good/fair/poor) ( 19 ), smoking status (self-reported as never, former or current), and total minutes of recreational physical activity (including mild, moderate, and strenuous physical activity). Most recent assessed body mass index (weight in kg/divided by height in m 2 ), was categorized as <18.5, 18.5–24.9, 25.0–29.9, and ≥30.0. History of noncancer comorbidities (yes vs no for each condition) was assessed annually using both selfreport (diabetes treated with pills or insulin, coronary heart disease, stroke, hip fracture after age 55 years, chronic obstructive pulmonary disease, and osteoarthritis) and clinical adjudication for primary WHI outcomes during the main WHI study and the first extension (coronary heart disease, stroke, and hip fracture). Finally, we also included WHI study assignment as an additional covariate (clinical trial vs observational study).
Psychosocial variables.
Positive and negative psychosocial variables such depression and optimism have been found to be significant predictors of physical functioning and quality of life in prior studies of older adults with and without chronic medical conditions ( 12–14 ). Depressive symptoms were measured by the 8-item Burnham short version of the CESD-D 23 . Responses for each item were weighted according to the Burnham algorithm with a final range from 0 to 1; higher score indicates greater likelihood of depression. Scores >.06 are considered indicative of significant depressive symptoms, and scores ≤.06 indicative of no/minimal depressive symptoms. Optimism was measured using the life orientation test-revised ( 24 ). Scores range from 6 to 30, with higher score indicating greater optimism. We created quartiles of optimism using cut-offs derived from this sample of 80+ women. Subjective happiness was assessed using a single item from the emotional well-being subscale of the Rand-36 asking women about their happiness during the past 4 weeks. We compared those who responded all/most of the time versus a good bit/some versus a little bit/none based on the distribution of responses. The most recent participant assessments after cancer diagnosis were used for depressive symptoms, subjective happiness, and optimism.
Statistical Analysis
Women in the 80+ cohort were categorized with respect to presence versus absence of cancer. Women’s characteristics were described as means ( SD ) for continuous variables or counts (percentage) for categorical variables. Comparisons across women with and without a history of cancer were performed using analysis of variance for continuous variables or chi-square tests for categorical variables. First, analysis of covariance was used to examine the effect of cancer history on physical function, with and without adjustment for race/ethnicity, education, marital status, WHI study assignment, health behaviors (BMI, tobacco use, and physical activity), self-reported health, noncancer comorbidities, and psychological variables (depressive symptoms, optimism, and subjective happiness). Finally, we also explored possible independent predictors for physical functioning among cancer survivors using an analysis of covariance model, including cancer type, cancer stage, age at first cancer diagnosis and time since most recent cancer diagnosis as described in Table 1 . Similar analysis was also performed for women without a cancer history. Least square means and their corresponding SEs were reported from all the analysis of covariance models. p < 0.005 was considered significant to account for multiple comparisons.
Table 1.
Multivariable predictors of physical functioning among women 80 years and older ( N = 22,650), stratified by cancer status
| Characteristics | Category | Cancer History N = 2,270 | No Cancer History N = 20,380 | Interaction p -Value | ||
|---|---|---|---|---|---|---|
| LS Mean ( SE ) | p -Value | LS Mean ( SE ) | p -Value | |||
| Current age (years) | 80–84 (ref) | 58.2 (0.6 ) | <.0001 | 61.0 (0.2 ) | <.0001 | 0.54 |
| 85–89 | 52.3 (0.8)* | 55.3 (0.3)* | ||||
| 90+ | 43.7 (1.7)* | 48.8 (0.5)* | ||||
| Race/ethnicity | Asian or Pacific Islander | 54.6(3.5) | .17 | 59.2 (1.1) | <.0001 | 0.71 |
| Black or African American | 61.5(3.0) | 61.4 (0.7)* | ||||
| Hispanic/Latino | 50.3 (4.9) | 61.6 (1.2)* | ||||
| White (not of Hispanic origin, ref) | 55.1 (0.5) | 57.9 (0.2) | ||||
| Other | 59.0 (4.3) | 61.7 (1.4)* | ||||
| Education | High school or less | 54.8 (1.1) | .67 | 58.7 (0.3) | .06 | 0.07 |
| Above high school | 55.4 (0.5) | 58.0 (0.2) | ||||
| Marital status | Not married | 53.8(0.8) | .03 | 58.0 (0.3) | .33 | 0.03 |
| Married or intimate | 56.0(0.5) | 58.3 (0.2) | ||||
| Observational study cohort | No | 56.1 (0.7) | .11 | 59.0 (0.2) | <.0001 | 0.39 |
| Yes | 54.6 (0.6) | 57.6 (0.2) | ||||
| BMI (kg/m 2 ) | <18.5 | 58.4 (4.0 ) | <.0001 | 62.7 (1.3 ) | <.0001 | 0.32 |
| 18.5–24.9 (ref) | 61.0 (0.7 ) | 63.0 (0.2 ) | ||||
| 25–29.9 | 54.1 (0.8)* | 57.8 (0.3)* | ||||
| 30+ | 47.2 (1.0)* | 49.4 (0.3)* | ||||
| Smoking status | Never (ref) | 55.4 (0.6) | .85 | 58.5 (0.2) | .05 | 0.50 |
| Current | 55.1 (0.6) | 57.8 (0.2)* | ||||
| Past | 58.5 (6.1) | 59.3 (1.4) | ||||
| Recreational physical activity (min/week) | 1 st quartile (ref) | 44.1 (0.9 ) | <.0001 | 46.7 (0.3 ) | <.0001 | 0.31 |
| 2 nd quartile | 54.3 (0.9)* | 56.5 (0.3)* | ||||
| 3 rd quartile | 58.6 (0.9)* | 61.1 (0.3)* | ||||
| 4 th quartile | 67.5 (1.0)* | 69.0 (0.3)* | ||||
| Self-rated Health | Excellent/very good/good | 58.1 (0.5 ) | <.0001 | 61.1 (0.2 ) | <.0001 | 0.01 |
| Fair/poor | 39.6 (1.2 ) | 39.2 (0.4 ) | ||||
| Noncancer comorbidity | ||||||
| Coronary heart disease | No | 55.8 (0.5 ) | .001 | 58.6 (0.2 ) | <.0001 | 0.66 |
| Yes | 51.0 (1.4 ) | 54.8 (0.5 ) | ||||
| Stroke | No | 55.5 (0.5 ) | .01 | 58.5 0.2 ) | <.0001 | 0.67 |
| Yes | 49.8 (2.2 ) | 51.5 (0.7 ) | ||||
| Treated diabetes | No | 55.4 (0.5) | .46 | 58.4 (0.2 ) | <.0001 | 0.45 |
| Yes | 54.5 (1.2) | 56.5 (0.4 ) | ||||
| Hip Fracture after 55 | No | 55.8 (0.5 ) | <.0001 | 58.7 (0.2 ) | <.0001 | 0.42 |
| Yes | 46.5 (1.8 ) | 48.7 (0.6 ) | ||||
| Chronic obstructive pulmonary disease | No | 55.6 (0.5 ) | .01 | 58.5 (0.2 ) | <.0001 | 0.84 |
| Yes | 51.3 (1.6 ) | 53.6 (0.6 ) | ||||
| Arthritis | No | 62.6 (0.9 ) | <.0001 | 65.0 (0.3 ) | <.0001 | 0.58 |
| Yes | 53.1 (0.5 ) | 56.1 (0.2 ) | ||||
| Subjective happiness | Most to all of the time | 56.1 (0.6)* | .005 | 59.3 (0.2)* | <.0001 | 0.29 |
| Some to a good bit of the time | 54.5 (0.8)* | 56.0 (0.3 ) | ||||
| None to a little of the time (ref) | 49.3 (2.1 ) | 55.3 (0.7 ) | ||||
| Depressive symptom | No | 55.4 (0.5) | .24 | 58.3 (0.2) | .06 | 0.60 |
| Yes | 53.2 (1.8) | 57.0 (0.6) | ||||
| Optimism | 1st quartile (ref) | 56.5 (1.0) | .07 | 58.5 (0.3) | .59 | 0.09 |
| 2nd quartile | 53.8 (0.9) | 58.1 (0.3) | ||||
| 3rd quartile | 54.4 (0.9) | 57.9 (0.3) | ||||
| 4th quartile | 56.4 (0.8) | 58.3 (0.3) | ||||
| Cancer type | Breast (ref) | 55.4 (0.6) | .87 | |||
| Colorectal | 56.6 (1.4) | |||||
| Uterine | 54.5 (1.7) | |||||
| Melanoma | 54.5 (1.5) | |||||
| Other | 55.2 (1.2) | |||||
| Multiple cancer | 54.0 (2.0) | |||||
| Time since most recent diagnosis (years) | ||||||
| 2–5. | 53.6 (0.8) | 05 | ||||
| 6–10 | 56.4 (0.7) | |||||
| 11+ (ref) | 55.4 (0.8) | |||||
| Cancer stage at diagnosis | In situ/localized regional | 55.3 (0.5) 55.3 (1.1) | .93 | |||
Bold values indicated that the p-value was less than .05 for the comparison with the reference group.
*Comparison with reference group, p -value < .05.
All analyses were performed using SAS 9.3 (Cary, NC). As part of an exploratory analysis, we also examined differences between those women with and without a cancer history for the individual items comprising the physical function scale.
Results
Composition of the analytic sample is shown in Figure 1 . The final sample for this analysis ( N = 22,650) included 20,380 women with no history of cancer and 2,270 women with a cancer history (5.2% had multiple cancers). Among the cancer survivors ( Table 2 ), most cancers were early stage at diagnosis (81.5% in situ or localized) and the most common cancer types included breast (53.5%), colorectal (11.1%), melanoma (9.1%), and uterine (6.8%). For the majority of women (71.7%), their 80+ physical functioning assessment occurred more than 5 years after their most recent cancer diagnosis (range= 2.0–17.3 years).
Figure 1.
Composition of the analytic sample of women age 80 years and older with and without a history of cancer.
Table 2.
Characteristics of women 80 years of age and older by cancer history (women’s health initiative cohort: N = 22,650)
| Characteristics | Category | Overall % | Cancer History*% | No Cancer History% | p -Value † |
|---|---|---|---|---|---|
| N | N = 22,650 | n = 2,270 | n = 20,380 | ||
| Current age (years) | 80–84 | 60.3 | 61.2 | 60.2 | .37 |
| 85–89 | 31.6 | 31.4 | 31.6 | ||
| 90+ | 8.1 | 7.4 | 8.2 | ||
| Race–ethnicity | Asian or Pacific Islander | 2.0 | 1.7 | 2.0 | <.0001 |
| Black or African American | 4.3 | 2.3 | 4.5 | ||
| Hispanic/Latino | 1.4 | 0.8 | 1.5 | ||
| White non-Hispanic | 91.1 | 94.1 | 90.7 | ||
| Other | 1.2 | 1.1 | 1.2 | ||
| Education level | High school or less | 21.1 | 17.2 | 21.5 | <.0001 |
| Marital status | Married | 65.5 | 67.7 | 65.2 | .02 |
| WHI study Assignment | Observational cohort | 57.4 | 57.7 | 57.3 | .74 |
| BMI (kg/m 2 ) | <18.5 | 1.3 | 1.2 | 1.3 | .05 |
| 18.5–24.9 | 41.2 | 40.7 | 41.2 | ||
| 25–29.9 | 35.7 | 34.0 | 35.9 | ||
| 30+ | 21.9 | 24.1 | 21.6 | ||
| Smoking status | Never | 55.5 | 51.0 | 56.1 | <.0001 |
| Past | 43.3 | 48.5 | 42.7 | ||
| Current | 1.1 | 0.5 | 1.2 | ||
| Recreational physical activity (min/week) | 1st quartile (median = 0) | 26.8 | 29.3 | 26.5 | .003 |
| 2nd quartile (median = 45) | 22.6 | 22.7 | 22.6 | ||
| 3rd quartile (median = 150) | 26.5 | 26.6 | 26.5 | ||
| 4th quartile (median = 330) | 24.1 | 21.4 | 24.4 | ||
| Self-rated health | Excellent/very good/Good | 86.5 | 84.9 | 86.6 | .02 |
| Fair/poor | 13.5 | 15.1 | 13.4 | ||
| Presence of noncancer comorbidities | % Yes | ||||
| Coronary heart disease | 11.0 | 10.5 | 11.0 | .44 | |
| Stroke | 4.6 | 4.1 | 4.6 | .29 | |
| Treated diabetes | 13.6 | 15.1 | 13.4 | .02 | |
| Hip fracture after 55 | 5.5 | 6.0 | 5.5 | .29 | |
| Chronic obstructive pulmonary disease | 7.4 | 7.7 | 7.4 | .67 | |
| Arthritis | 23.2 | 23.2 | 23.2 | .98 | |
| Optimism | 1st quartile | 21.9 | 19.6 | 22.2 | .01 |
| 2nd quartile | 24.8 | 25.8 | 24.7 | ||
| 3rd quartile | 24.8 | 24.1 | 24.8 | ||
| 4th quartile | 28.5 | 30.5 | 28.3 | ||
| Perceived happiness | Most to all of the time | 66.7 | 64.6 | 66.9 | .07 |
| Some to a good bit of the time | 28.3 | 30.4 | 28.1 | ||
| None to a little of the time | 5.0 | 5.0 | 5.0 | ||
| Depressive symptoms | Yes | 6.9 | 7.0 | 6.9 | .85 |
| Age at first cancer diagnosis (years) | 60–69 | 16.2 | |||
| 70–79 | 67.5 | ||||
| 80+ | 16.3 | ||||
| Cancer type | Breast | 53.5 | |||
| Colorectal | 11.1 | ||||
| Uterine | 6.8 | ||||
| Melanoma | 9.1 | ||||
| Other | 14.4 | ||||
| Multiple cancer | 5.2 | ||||
| Cancer stage | In situ/localized | 81.5 | |||
| Regional | 18.5 | ||||
| Time since most recent diagnosis (years) | 2–5 | 28.3 | |||
| 6–10 | 38.6 | ||||
| 11–17 | 33.1 |
*This group included women with an adjudicated history of cancer during their WHI study enrollment, excluding those with advanced or unknown cancer stages and those <24 months after date of any cancer diagnosis.
† Comparison between women with and without a history of cancer.
Differences Between Older Women With and Without a Cancer History
We observed modest, but statistically significant demographic differences between women in the 80+ cohort who did and did not have a history of cancer ( Table 2 ). Cancer survivors were more likely than the no cancer history group to be of non-Hispanic white ethnicity (94.1% vs 90.7%, p < .0001) and to report more than a high school education (82.8% vs 78.5%, p < .0001). Cancer survivors were also significantly more likely to report a past history of smoking (48.5% vs 42.7%) and to be in the lowest quartile of recreational physical activity (no activity) (29.3% vs 26.5%). There were no differences for noncancer comorbidities or psychological variables (optimism, subjective happiness, or depression).
Physical Functioning by Cancer History
Women with a history of cancer reported significantly lower mean ( SE ) physical functioning (55.3[0.6]) than those without a cancer history (58.2[0.2]: Table 3 ). These mean differences remained statistically significant and decreased slightly in magnitude in models that adjusted for demographics, health behaviors, health status, and psychological status. In the fully adjusted model, the least square means were 56.6 (0.4) for survivors and 58.0 (0.1) for women with no cancer history. There were no significant differences in physical functioning between survivors with single or multiple cancers in adjusted or unadjusted models (results not reported). In analyses exploring differences for individual items comprising the physical function scale, cancer survivors were significantly ( p < .005) more likely to report limitations for all items except lifting or carrying groceries ( p = .04) and bathing or dressing ( p = .55).
Table 3.
Physical functioning after age 80 among women by cancer history in the 80+ WHI cohort ( N = 22,650)
| RAND-36 Physical Functioning Subscale | Cancer History ( n = 2,270) LS Means ( SE ) | No Cancer History ( n = 20,380) LS Means ( SE ) | p -Value From Analysis of Covariance Model |
|---|---|---|---|
| Unadjusted | 55.3 (0.6) | 58.2 (0.2) | <.0001 |
| Adjusted* | 56.6 (0.4) | 58.0 (0.1) | .002 |
*Model was adjusted for race/ethnicity, education, marital status, WHI study cohort, BMI, tobacco use, physical activity, self-reported health, noncancer comorbidities, depressive symptoms, optimism, and subjective happiness.
Predictors of Physical Functioning Among Older Females With and Without a Cancer History
In general, predictors of physical functioning were similar in women with and without a cancer history unadjusted models shown in Supplementary Table and adjusted models shown in Table 1 , with no interactions reaching the .005 significance level. Predictors of better physical functioning in females with and without cancer included younger current age, under or normal weight, higher levels of physical activity, excellent/very good/good self-reported health, and absence of noncancer comorbidities. The largest decrements in physical functioning were observed for those women with stroke, hip fracture, and arthritis (least square means differences >5). All three psychological variables were significant predictors of physical functioning in the unadjusted model ( Supplementary Table ), but only subjective happiness remained statistically significant for both groups in adjusted models. Women with higher happiness reported better physical functioning after age 80 (difference between lowest and highest group least square means of 4.0 (no cancer) and 5.8 (cancer history).
There were no significant differences in physical functioning by cancer type, time since cancer diagnosis and cancer stage (in situ or localized vs regional) among the cancer survivors ( Table 1 ).
Discussion
Cancer history is associated with poorer self-reported physical functioning among women 80 years of age and older, and adjustment for demographics, health behaviors, health status, and psychological variables does not eliminate this effect. The size of the difference in physical functioning between older women with and without a cancer history (1.4 points in adjusted models) is approximately 15%, but does not reach the half a SD difference that is often considered clinically meaningful ( 25 ). Importantly, these interpretation rules are meant to assess differences over time for one individual, but do not reflect population perspectives that acknowledge that relatively small differences in risk factors or outcomes may have large implications when applied to populations. Very little is known about the meaningfulness about population differences in physical functioning, with most studies relying on interpretation based on individual change metrics. Predictors of better physical functioning were similar in older women with and without a cancer history in fully adjusted models (younger age, increased physical activity, healthy weight, better self-reported health, absence of noncancer comorbidities, and subjective happiness). Many of these same predictors of physical functioning or related constructs such as frailty have been seen in the general population of older adults ( 26–29 ) and in other studies of cancer survivors ( 5 , 30 ).
Similar to Bellury and colleagues ( 5 ), we observed that psychological status (in our case, subjective happiness) was associated with physical functioning in cancer survivors. Both optimism and significant depressive symptoms were significantly associated with physical functioning in unadjusted, but not adjusted models. Consistent with this finding, in prior studies that have examined positive psychological functioning in the general population of older adults, greater positive psychological well-being/positive affect have demonstrated significant associations with improved health outcomes including fewer reported physical symptoms, fewer comorbidities, lower risk of functional impairment, better self-rated health, biological correlates that may protect health, and lower mortality ( 31–36 ). Such findings have been significant even after controlling for sociodemographic variables, health behaviors, depressive symptoms, and negative affect ( 35 , 36 ). Our results provide further evidence that positive emotions are an independent predictor of health outcomes ( 37 ).
Noncancer comorbidities were important predictors of physical functioning among female survivors 80 years and older. With the exception of treated diabetes, the impact on physical functioning of each individual noncancer comorbidity approached or exceeded 1/2 SD . The importance of noncancer comorbidities on physical functioning has been also been observed in other samples of cancer survivors who were generally younger than our 80+ cancer survivors ( 9 , 10 ). These findings suggest that noncancer comorbidities continue to have a critical impact on physical functioning, even among these oldest old survivors (see also Rillamas Sun and colleagues, this issue, for further data on impact of comorbidities in the 80+ cohort).
Interestingly, unlike Paskett and colleagues’ ( 38 ) analysis of women with a history of cancer at WHI study entry, we did not observe poorer physical functioning among African American or other minority survivors compared to white, non-Hispanic female cancer survivors in our 80+ cohort. Our finding is also at odds with other data suggesting higher prevalence of noncancer comorbidities and poorer functional health among African American survivors ( 39 ), but may be explained by survival bias. Women who survive to age 80 are likely to be healthier than those who did not survive and race/ethnicity differences may be less apparent among the 80+ cohort. Cené and colleagues explore race/ethnicity differences further in this same journal issue.
By design, this study excluded women who did not survive to age 80, survivors who entered the WHI with a history of cancer, and women with advanced stage disease. However, our findings are relevant to those females aged 80 and above who are increasingly seen in oncology follow-up clinics and primary care clinics for on-going survivorship care. Study strengths include the large sample size(to our review, the largest study of 80+ female cancer survivors to date), adjudicated cancer diagnoses, a control population without a cancer history, and information on potential mediating/associated factors of the physical function measures. Study limitations include lack of information on cancer therapy, recurrence, and permanent bodily changes due to cancer. Objectively measured physical performance was available for only a small subset of participants and could not be used in the present analyses; future analyses incorporating this additional data could provide additional insight into differences in physical function between octagenarians with and without a cancer history. In addition, this analysis does not fully assess the directionality of the observed effects, particularly among physical activity, overweight/obesity, and physical functioning. Longitudinal studies that examine trajectories of physical functioning and health behaviors may elucidate these complex relationships in older female cancer survivors. Finally, future examination of the relationship between cancer and physical functioning in an expanded cohort including younger women would also be informative.
Understanding the functional consequences of a cancer diagnosis among the oldest old can inform development of individualized survivorship plans. Our study suggests that the oldest cancer survivors may continue to benefit from healthy behaviors to improve physical functioning, including physical activity and maintenance of a healthy weight. Consideration of psychosocial factors such as happiness may also be important. Overall, our study suggests resilience among the population of older female cancer survivors. Although physical functioning was slightly lower in survivors compared to older women without a cancer history, the differences were smaller than one might expect. Clinicians caring for these older survivors should continue to remain cognizant of the critical role of noncancer comorbidities for survivors in their 80s and beyond. Assessing and addressing health promoting behaviors in female oncology survivors, regardless of age, continue to be important in the preservation of physical functioning, particularly in those 80 years and older.
Funding
The WHI program is funded by the National Heart, Lung, and Blood Institute at the National Institutes of Health, U.S. Department of Health and Human Services through contracts HHSN268201100046C, HHSN268201100001C, HHSN26820 1100002C, HHSN268201100003C, HHSN268201100004C, and HHSN271201100004C.
Supplementary Material
Acknowledgments
We gratefully acknowledge the dedicated efforts of the WHI participants and of key WHI investigators and staff at the clinical centers and the Clinical Coordinating Center. A full listing of the WHI investigators can be found at https://cleo.whi.org/researchers/Documents%20%20Write%20a%20Paper/WHI%20Investigator%20Long%20List.pdf .
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