Abstract
Abstract
Objectives
To identify risk factors and examine associations between colorectal cancer (CRC) status and modifiable and non-modifiable risk factors among patients diagnosed in Oman, considering the existence and increase of incidence and prevalence of these risk factors.
Design
A multicentre case–control study.
Setting
Sultan Qaboos University Hospital and the Royal Hospital in Muscat, Oman.
Participants
Patients diagnosed with CRC (n=166) and controls (n=166).
Outcome measures
A questionnaire adapted from the Colon Cancer Family Registry and other previously published studies was used to collect data on sociodemographic characteristics, modifiable and non-modifiable CRC risk factors and coexisting morbidities. Univariable and multivariable logistic regression analyses were performed to examine associations between CRC status and independent variables.
Results
Multivariable analysis demonstrated significant associations between CRC status and several risk factors. Smoking was associated with a fourfold increased risk of CRC (adjusted OR (aOR): 4.35, 95% CI 2.26 to 8.36). Higher body mass index was also associated with increased CRC risk (aOR: 2.42, 95% CI 1.23 to 4.76), while individuals with a family history of CRC, including first-degree relatives (biological parents, siblings and children) and second-degree relatives (grandparents, uncles and aunts) had more than double the risk (aOR: 2.10, 95% CI 1.15 to 3.82). Also, polyps had double the risk (aOR 2.61, 95% CI 1.40 to 4.84) In addition, CRC was more common among patients with diabetes (aOR 2.70, 95% CI 1.52 to 4.80), hypertension (aOR 4.13, 95% CI 2.03 to 8.42) and inflammatory bowel disease (aOR 3.48, 95% CI 1.13 to 10.67).
Conclusions
Considering the existence of non-modifiable risk factors and the increase in incidence and prevalence of modifiable risk factors of CRC in Oman, the findings of this study underscore the need for targeted awareness initiatives, risk-based screening and early surveillance, particularly among high-risk groups. The results also support integrating smoking cessation, weight management and optimal control of chronic diseases into national CRC prevention programmes to reduce the overall CRC disease burden.
Keywords: Risk Factors, Cross-Sectional Studies, Cancer, Epidemiology, Gastrointestinal tumours
STRENGTHS AND LIMITATIONS OF THIS STUDY.
Patients diagnosed with colorectal cancer (CRC) and control group were recruited from two main referred tertiary care hospitals in Oman.
Genetic and sociodemographic risk factors for CRC were studied in patients and control group. Data were collected from hospital information systems and supplemented by participant contact to obtain missing sociodemographic details and both modifiable and non-modifiable CRC risk factors.
The results may be subject to recall bias, particularly for self-reported dietary intake, changes in physical activity following diagnosis and information on culturally sensitive behaviours, which may have affected the accuracy of some observed associations.
Background
Colorectal cancer (CRC) remains a major global health concern and currently ranks as the third most prevalent malignancy and the second leading cause of cancer-related death.1 Projections indicate a continued rise in incidence, with estimates suggesting an additional 3.2 million new cases and 1.6 million deaths by 2040.2 This malignancy is characterised by heterogeneity, encompassing multiple molecular pathways and pathogenic events.3 The most common type of CRC is adenocarcinoma, accounting for 90%–95% of all CRC cases worldwide.4 The aetiology of CRC is complex and multifactorial, influenced by both modifiable and non-modifiable risk factors, as well as chronic gastrointestinal conditions such as inflammatory bowel disease (IBD) and colorectal polyps, alongside various comorbidities.5
Non-modifiable risk factors for CRC are well-documented and include age, sex, family history of CRC, (Family history of CRC was defined as having one or more first-degree relatives biological parents, siblings or children or second-degree relatives (grandparents, uncles or aunts) with a confirmed diagnosis of CRC), hereditary genetic syndromes, familial adenomatous polyposis, Peutz-Jeghers syndrome and juvenile polyposis syndrome.6 In addition, several modifiable risk factors have been associated with an increased risk of CRC, including smoking, alcohol consumption, elevated body mass index (BMI) and high red meat intake.7 Other comorbid conditions have also been linked, such as type 2 diabetes, cardiovascular disease, metabolic syndrome, insulin resistance and oxidative stress.8 9 Given the interconnected nature of CRC risk factors, comprehensive prevention strategies are imperative, integrating lifestyle modification, effective management of chronic diseases and early screening initiatives.9
Within the Middle East and North Africa region, the incidence of CRC ranges from 15 to 36 per 100 000 and is projected to rise substantially by 2040.10 11 In Oman, CRC is the most prevalent cancer among males and the third most common among females.12 Studies in Oman, the Gulf, and other Arab populations have shown an increased incidence of patients diagnosed with CRC at a younger age (before age of 50 years) compared with global rates, reflecting a concerning shift in age distribution.10 13 Furthermore, rapid lifestyle and sociodemographic changes in Oman, the Gulf and other Arab populations have been implicated in influencing CRC epidemiology.13 However, a previous study conducted in Oman reported mixed and contradictory findings, with no significant differences observed between patients diagnosed with CRC and controls in relation to risk factors such as smoking, alcohol intake, physical activity and dietary fibre intake. Nevertheless, the study found that patients diagnosed with CRC were more likely to be overweight, have higher caloric and macronutrient intake (carbohydrates, protein and saturated fat) and low intake of vegetables and fruits compared with controls.14 Understanding both modifiable and non-modifiable risk factors within the Omani population is crucial for developing effective prevention, enabling early detection, supporting personalised screening and guiding national screening initiatives in Oman.
Increased awareness of modifiable factors has the potential to significantly reduce disease incidence. Moreover, recognition of non-modifiable risk factors enables clinicians to identify high-risk individuals and implement personalised screening and surveillance protocols. Collectively, this approach enhances risk stratification, supports evidence-based clinical decision-making and informs public health initiatives aimed at reducing the overall burden of CRC in the country. Therefore, the aim of this study was to identify modifiable and non-modifiable risk factors among patients diagnosed with CRC in Oman, particularly given the presence and increased incidence and prevalence of these risk factors in the country.
Methods
Study design and setting
This study forms part of a larger research project, from which some findings have been previously published: the region-wise distribution of molecular subtypes of CRC in Oman.15 A case–control study was conducted from 1 September 2024 to 31 July 2025 at two major government hospitals in Oman: Sultan Qaboos University Hospital (SQUH) and the Royal Hospital (RH). Both hospitals are tertiary care hospitals located in Muscat, the capital city of Oman, providing highly specialised medical, surgical and oncological services, and serving as key institutions for clinical teaching and research. Both hospitals accept patients referred from local primary health centres of Muscat governorate and from secondary care hospitals across all regions of Oman for specialist services, when such services are unavailable at the secondary care level in the regions or when higher-level medical expertise is required.
Within the Omani healthcare system, primary healthcare centres provide preventive services, management of common medical conditions and initial assessment of symptoms. Patients presenting with suspected colorectal symptoms may undergo initial laboratory investigations and clinical assessment before referral. Secondary hospitals provide specialist medical and surgical services including general gastroenterology and diagnostic evaluation. However, advanced endoscopy, subspecialised IBD services, multidisciplinary oncology care and complex colorectal management are largely concentrated within tertiary referral centres such as SQUH and RH. Consequently, patients referred to these centres may represent a selected subgroup with more complex presentations or specialised healthcare needs.
Inclusion criteria
Patients who visited the outpatient gastroenterology departments of SQUH and RH Muscat. The patients included adult Omanis who consented and were suspected of having CRC; they all had undergone colonoscopy and biopsy or resection, and were included in the studies. Patients who had tissue analysis and histological diagnosis were selected as cases. The control group comprised patients recruited from the same hospitals during the same study period who underwent colonoscopy and had normal histological findings. Controls were selected from the same clinical setting as cases to improve comparability; however, no formal individual matching procedure was performed.
Exclusion criteria
Patients who had other cancers other than CRC, non-Omani patients and patients less than 18 years of age were excluded from the study.
Tools of measurement
A questionnaire adapted from the Colon Cancer Family Registry and other previously published research studies was used for data collection.16 17 The questionnaire comprised four sections: (A) sociodemographic characteristics, (B) modifiable risk factors, (C) non-modifiable risk factors and (D) information on chronic gastrointestinal diseases, including IBD and colorectal polyps, as well as comorbid conditions such as diabetes mellitus, hypertension and ischaemic heart disease (IHD) (online supplemental appendix 1). Meat intake was considered as follows: no meat or rare intake was recorded as 1; three times or more per week was recorded as 2; and the values were recalled over the past year. The developed questionnaire was reviewed by co-authors with expertise in gastroenterology, pathology and public health. It was translated into Arabic and subsequently back-translated into English by independent translators to ensure the accuracy of both language and meaning. The questionnaire was piloted among the first 20 participants, and reliability testing demonstrated good internal consistency (Cronbach’s alpha=0.79).
Participants
Consenting adult Omani patients (aged 18 years and above) who attended the outpatient gastroenterology departments at SQUH and RH during the study period (1 September 2024 to 31 July 2025) for colonoscopy due to suspected CRC, whether referred from the same institutions, other primary care settings or secondary hospitals across other regions of Oman, were approached by the researcher and invited to participate in the study. The purpose of the study was explained, and the confidentiality of the collected information was assured. Participants were provided with an information sheet detailing the study and were given the opportunity to ask questions. Those who agreed to participate were asked to sign a written informed consent form.
All consenting individuals who underwent colonoscopy, biopsy or surgical resection and had a histologically confirmed diagnosis of adenocarcinoma were enrolled as cases.
Controls were selected from the same clinical setting as cases to improve comparability; however, no formal individual matching procedure was performed. The control group comprised patients who underwent colonoscopy during the same period and had normal histological findings. There were no incentives given to the participants.
Data collection
Data were primarily extracted from hospital healthcare information systems (TrakCare at SQUH and Al-Shifa at RH), including demographic, clinical and diagnostic information. Participants were contacted by telephone only when additional information unavailable in medical records was required, including selected sociodemographic variables, smoking status, alcohol consumption, physical activity, dietary habits and family history of CRC. Therefore, the questionnaire was used as a supplementary tool to complete missing data rather than being administered entirely by telephone. Participants’ non-response was mainly due to refusal without explanation, although some declined due to time constraints and social inhibition. No incentives are offered to the patients for responses.
Sample size and power calculation
The sample size was calculated using EPITOOLS software (AusVet, Canberra, Australia).18 The assumptions for sample size estimation were informed by previously published CRC case–control studies reporting exposure prevalence and effect estimates for CRC-associated risk factors in regional populations.14 16 To achieve a significance level (type I error) of 5% and a 95% CI, assuming an estimated exposure prevalence of 10% among controls and a minimum detectable OR of 2.43 at a case-to-control ratio of 1:1, a total sample size of 332 participants (166 cases and 166 controls) was required to achieve 80% statistical power.
Statistical analysis
Statistical analyses were conducted using SPSS software, V.23 (IBM). Quantitative variables such as age and BMI were categorised based on standard clinical thresholds (age ≤50 vs >50 years; BMI <25 vs ≥25 kg/m²) for analysis. Univariable and multivariable logistic regression analyses were performed to assess associations between CRC status and independent variables. Variables significant in the univariable analysis were included in the multivariable model. Crude ORs and adjusted ORs (aORs), with their corresponding 95% CIs, were calculated to evaluate the precision and reliability of associations. A significance level of 5% was used, with p<0.05 considered statistically significant.
Descriptive statistics were used to summarise participant characteristics. Sociodemographic and disease-related characteristics between cases and controls were compared using Pearson’s χ2 test for categorical variables. Quantitative variables such as age and BMI were categorised according to predefined clinical thresholds before analysis. Univariable and multivariable logistic regression analyses were subsequently performed to assess associations between CRC status and independent variables.
Patient and public involvement
None.
Results
Participant characteristics
A total of 350 patients were invited to participate, of whom 332 consented and were included in the analysis (response rate: 94.9%). Participant non-response was mainly due to refusal without explanation, although some participants declined due to time constraints. Table 1 presents the sociodemographic characteristics of the participants. Ages ranged from 24 to 94 years, with a mean of 59.14 years. Most participants were married (cases: 75.3%; controls: 88.6%), had primary or secondary education (cases: 45.8%; controls: 36.7%), and were unemployed or retired (cases: 78.3%; controls: 63.9%). Regarding smoking, cases 33.1%; controls 11.4% were smokers. Physical activity (cases 50%; controls 46.4%), they were inactive or just walked around the house, and (cases 50% and controls 53.3%) were doing low to high intensity physical activity. Alcohol consumption (cases 2.4%; controls 3.6%) were consuming alcohol. BMI (cases: 24.7%; controls: 12%) was 26 or more. The frequency of meat intake was measured as follows: no meat or rare intake was recorded as 1; three times or more per week was recorded as 2; and the values were recalled over the past year.
Table 1. Sociodemographic characteristics (N=332).
| Characteristic, n (%) | Cases (n=166) | Controls (n=166) | P value* |
|---|---|---|---|
| Gender | 0.66 | ||
| Male | 87 (52.4) | 91 (54.8) | |
| Female | 79 (47.6) | 75 (45.2) | |
| Age, years | 0.38 | ||
| ≤50 | 40 (24.1) | 47 (36.7) | |
| ≥50 | 126 (75.9) | 119 (71.7) | |
| Marital status | 0.00 | ||
| Single | 8 (4.8) | 4 (2.4) | |
| Married | 125 (75.3) | 147 (88.6) | |
| Widowed/divorced/separated | 33 (19.9) | 15 (9.0) | |
| Education level | 0.03 | ||
| No formal education | 63 (38.0) | 59 (35.5) | |
| Primary/secondary | 76 (45.8) | 61 (36.7) | |
| Bachelor’s degree or higher | 27 (16.3) | 46 (27.7) | |
| Employment status | |||
| Employed | 36 (21.7) | 60 (36.1) | 0.00 |
| Unemployed/retired | 130 (78.3) | 106 (63.9) | |
| Smoking | |||
| Smoker | 55 (33.1%) | 19 (11.4%) | 0.00 |
| Non smoker | 111 (68.9%) | 147 (88.6%) | |
| Physical activity | |||
| No activity or walking around the house | 83 (50%) | 77 (46.4%) | 0.51 |
| Low to high intensity | 83 (50%) | 89 (53.6%) | |
| Alcohol | |||
| Alcohol drinking yes | 4 (2.4%) | 6 (3.6%) | 0.52 |
| Alcohol drinking No | 162 (97.6%) | 160 (96.4%) | |
| BMI | |||
| BMI 26 or more | 41 (24.7%) | 20 (12%) | 0.00 |
| BMI 25 and less | 125 (75.3%) | 146 (88%) | |
| Red meat | |||
| Once a week or less frequently | 154 (92.8%) | 162 (97.6%) | 0.04 |
| Twice a week or more frequently | 12 (7.2%) | 4 (2.4%) |
Calculated using a χ2 test.
BMI, body mass index.
The prevalence of CRC was higher among males than females (52.4% vs 47.6%) and was more common in participants 50 years or older compared with those under 50 years (75.9% vs 24.1%). Among CRC cases, tumours were most frequently located in the sigmoid colon (33.7%), followed by the rectum (19.9%), right colon (19.3%), descending colon (14.5%) and transverse colon (12.7%). The most commonly reported comorbidities were diabetes mellitus (37.3%), colorectal polyps (33.1%), hypertension (27.7%), IBD (10.2%) and IHD (7.8%).
Univariable logistic regression analysis
Table 2 shows the results of the univariable logistic regression analysis. Smoking was strongly associated with CRC, with smokers having markedly higher odds of CRC compared with controls (OR: 3.83; 95% CI 2.15 to 6.82; p<0.00). Consumption of red meat three times per week or more was also significantly associated with CRC (OR: 0.31; 95% CI 0.10 to 1.00; p=0.04). Participants with hypertension had a fourfold increased risk of CRC (OR: 4.16; 95% CI 2.18 to 7.92; p<0.001), while diabetes was associated with a twofold increased risk (OR: 2.49; 95% CI 1.51 to 4.10; p<0.001). Cases with IBD were nearly four times more likely to have the disease compared with controls (OR: 3.67; 95% CI 1.32 to 10.20; p=0.00).
Table 2. Univariable logistic regression analysis of factors associated with colorectal cancer status (N=332).
| Factor, n (%) | Cases (n=166) | Controls (n=166) | Unadjusted OR | 95% CI | P value | |
|---|---|---|---|---|---|---|
| Lower | Upper | |||||
| Age | ||||||
| Yes=less than 50 | 40 (24.1) | 47 (28.3) | 0.80 | 0.49 | 1.31 | 0.38 |
| No=more than 50 | 126 (75.9) | 119 (71.7) | ||||
| Gender | 0.90 | 0.59 | 1.39 | 0.66 | ||
| Male | 87 (52.4) | 91 (54.8) | ||||
| Female | 79 (47.6) | 75 (45.2) | ||||
| Smoking | 3.83 | 2.15 | 6.82 | <0.00 | ||
| Yes | 55 (33.1) | 19 (11.4) | ||||
| No | 111 (66.9) | 147 (88.6) | ||||
| Consumption of red meat | 0.31 | 0.10 | 1.00 | 0.04 | ||
| Once a week or less frequently | 154 (92.8) | 162 (97.6) | ||||
| Twice a week or more frequently | 12 (7.2) | 4 (2.4) | ||||
| HTN | 4.16 | 2.18 | 7.92 | <0.00 | ||
| Yes | 46 (27.7) | 14 (8.4) | ||||
| No | 120 (72.3) | 152 (91.6) | ||||
| Diabetes | 2.49 | 1.51 | 4.10 | <0.00 | ||
| Yes | 62 (37.3) | 32 (19.3) | ||||
| No | 104 (62.7) | 134 (80.7) | ||||
| IBD | 3.67 | 1.32 | 10.20 | 0.00 | ||
| Yes | 17 (10.2) | 5 (3.0) | ||||
| No | 149 (89.8) | 161 (97.0) | ||||
| Family history of colorectal cancer (first-degree relatives: biological parents, siblings, children and second-degree relatives: grandparents, uncles, aunts) |
2.31 | 1.37 | 3.89 | 0.00 | ||
| Yes | 53 (31.9) | 28 (16.9) | ||||
| No | 113 (68.1) | 138 (83.1) | ||||
| BMI | 2.39 | 1.33 | 4.33 | 0.00 | ||
| BMI 26 kg/m2 or more | 41 (24.7) | 20 (12.0) | ||||
| BMI 25 kg/m2 or less | 125 (75.3) | 146 (88.0) | ||||
| Polyps | 3.42 | 1.95 | 5.99 | <0.00 | ||
| Yes | 55 (33.1) | 21 (12.7) | ||||
| No | 111 (66.9) | 145 (87.3) | ||||
| Physical activity | 1.15 | 0.75 | 1.77 | 0.51 | ||
| None/walking around | 83 (50.0) | 77 (46.4) | ||||
| Moderate to high intensity | 83 (50.0) | 89 (53.6) | ||||
| Alcohol consumption | 0.65 | 0.18 | 2.33 | 0.52 | ||
| Yes | 4 (2.4) | 6 (3.6) | ||||
| No | 162 (97.6) | 160 (96.4) | ||||
| IHD | 1.93 | 0.75 | 4.96 | 0.16 | ||
| Yes | 13 (7.8) | 7 (4.2) | ||||
| No | 153 (92.2) | 159 (95.8) | ||||
| Parental consanguinity | 0.62 | 0.39 | 0.99 | 0.48 | ||
| Yes | 47 (28.3) | 64 (38.6) | ||||
| No | 119 (71.7) | 102 (61.4) | ||||
BMI, body mass index; HTN, hypertension; IBD, inflammatory bowel disease; IHD, ischaemic heart disease.
A family history of CRC (those who had relatives with a confirmed history of CRC) was also a significant risk factor, with affected individuals being twice as likely to develop CRC (OR: 2.31; 95% CI 1.37 to 3.89; p=0.001). Participants with elevated BMI had a twofold increased likelihood of CRC (OR: 2.39; 95% CI 1.33 to 4.33; p=0.003). The presence of colorectal polyps was strongly associated with CRC, with cases showing a threefold higher risk than controls (OR: 3.421; 95% CI 1.95 to 5.99; p<0.001). No significant associations were observed between CRC status and physical activity, alcohol consumption, IHD or parental consanguinity and age and gender.
Multivariable logistic regression model
Table 3 presents the multivariable logistic regression results. Smokers had a fourfold increased likelihood of developing CRC (aOR: 4.35, CI 2.26 to 8.36). Individuals with elevated BMI also exhibited a significantly increased risk (aOR: 2.42, CI 1.23 to 4.76). A family history of CRC continued to be a strong predictor (aOR: 2.10, CI 1.15 to 3.82). Polyps=aOR 2.61, CI 1.40 to 4.84. Furthermore, diabetes (aOR: 2.70, CI 1.52 to 4.80) hypertension (aOR: 4.13, CI 2.03 to 8.42) and IBD (aOR: 3.48, CI 1.13 to 10.67 were independently associated with a higher likelihood of CRC compared with controls.
Table 3. Multivariable logistic regression analysis of factors associated with colorectal cancer status in a hospital-based case–control study (N=332).
| Variable | Sig. | Unadjusted OR | Adjusted OR | 95% CI | |
|---|---|---|---|---|---|
| Lower | Upper | ||||
| Smoking | 0.00 | 3.83 | 4.35 | 2.26 | 8.36 |
| BMI | 0.00 | 2.39 | 2.42 | 1.23 | 4.76 |
| Family history of colorectal cancer (first-degree relatives: biological parents, siblings, children and second-degree relatives: grandparents, uncles, aunts) |
0.00 | 2.31 | 2.10 | 1.15 | 3.82 |
| Diabetes | 0.00 | 2.49 | 2.70 | 1.52 | 4.80 |
| HTN | 0.00 | 4.16 | 4.13 | 2.03 | 8.42 |
| IBD | 0.01 | 3.67 | 3.48 | 1.13 | 10.67 |
| Polyps | 0.00 | 3.42 | 2.61 | 1.40 | 4.84 |
| Consumption of red meat | 0.08 | 0.31 | 0.69 | 0.19 | 2.49 |
BMI, body mass index; HTN, hypertension; IBD, inflammatory bowel disease.
Discussion
This is a case–control study in Oman that examined modifiable and non-modifiable risk factors among Omani patients diagnosed with CRC. In this study, smoking, elevated BMI, family history of CRC, diabetes mellitus, hypertension, IBD, colorectal polyps and red meat consumption were all significantly associated with CRC status, with several of these variables remaining independent predictors in the multivariable analysis. Although the prevalence of smoking in Oman has increased in recent years, reaching 8.0% in 2020, it remains lower than that reported in neighbouring Gulf countries such as Saudi Arabia (21.4%) and Kuwait (26%).19 20 Nonetheless, the incidence of CRC in Oman is expected to rise in parallel with the upward trend in smoking prevalence.
A significant association between BMI and CRC was also observed in this study. Rapid economic growth in Oman has improved living standards but also contributed to unhealthy lifestyle changes, such as poor diet and increased sedentary behaviours, which have driven rising obesity rates.21 A recent community-based survey reported that almost two-thirds (66%) of the population was overweight or obese (BMI≥25 kg/m2).22 The increasing prevalence of overweight, obesity and sedentary behaviour in Oman represents a public health concern as these are well-established contributors to CRC risk.
In this study, elevated red meat intake, particularly three times per week or more, was significantly associated with CRC status. Frequent consumption of red meat likely raises CRC risk through multiple complementary mechanisms. Traditional cooking practices in Oman and other Arab countries, including charcoal grilling and regional preparations such as shuwa, mandi and kebab, expose meat to intense heat and smoke, which are human carcinogens.23
A positive family history of CRC (those who had confirmed CRC in the family) was associated with an approximately twofold increase in risk, underscoring the important contribution of genetic predisposition to CRC development. This finding is consistent with evidence showing that individuals with an affected first-degree relative have a significantly higher CRC risk.24 Similar associations have been reported in Middle Eastern populations, including Oman, where familial clustering highlights the relevance of genetic predisposition alongside shared dietary and lifestyle exposures, reinforcing the importance of family history as a key risk stratification factor for screening and prevention.14
Colorectal polyps were associated with an approximately threefold increased risk of CRC, consistent with the well-established adenoma-carcinoma sequence and studies reporting a high prevalence of colorectal polyps among patients with early-onset CRC.25 This observation reinforces the importance of individualised screening strategies and robust polyp surveillance programmes in Oman.
Patients with type 2 diabetes mellitus in this study had an approximately twofold increase in CRC risk. Colorectal adenomas have been reported in 42% of patients with type 2 diabetes, suggesting an independent association with adenoma development.25 Metabolic syndrome, often accompanying obesity, has been shown to increase CRC risk by approximately 36%.26 Furthermore, patients with both CRC and diabetes exhibit a 17% increased risk of all-cause mortality and a 12% increased risk of cancer-specific mortality, with poorer disease-free survival compared with their non-diabetic counterparts.27 In Oman, where the prevalence of type 2 diabetes mellitus is estimated at 15.7% with an additional 11.8% having pre-diabetes, these findings support the need for intensified CRC screening, particularly among patients with diabetes.28
Hypertension was associated with a fourfold increase in CRC risk, which is consistent with evidence from a meta-analysis showing a positive association between hypertension and CRC, with higher risk observed in men.29 Variations in effect size may reflect population-specific risk profiles, clustering of cardiometabolic comorbidities or residual confounding factors such as obesity, physical inactivity and medication use, highlighting the importance of blood pressure control in CRC prevention strategies.
Furthermore, IBD, including both ulcerative colitis and Crohn’s disease, was identified as a significant risk factor for CRC, with affected individuals exhibiting more than a threefold elevated risk compared with controls. This aligns with global evidence demonstrating that long-standing intestinal inflammation plays a central role in carcinogenesis, early dysplasia, and progression to CRC.30 Both referral hospitals, SQUH and RH, have developed an IBD service.
The multicentre case–control design and the use of multivariable logistic regression strengthened the internal validity of this study by enabling simultaneous assessment of the independent associations of CRC status with multiple modifiable and non-modifiable risk factors. However, several limitations must be acknowledged. First, although we have selected patients from the two major government oncology hospitals in Oman, SQUH and RH, which receive referred patients from across all regions of Oman, our sample does not represent the community, particularly for the control group, which limits population generalisability. Second, there was a recall bias, particularly regarding dietary intake, smoking, physical activity and alcohol consumption.
Third, some participants reported engaging in physical activity before diagnosis but subsequently stopping, which may have influenced classification accuracy. Fourthly, information bias is also possible for culturally sensitive behaviours such as alcohol consumption, where under-reporting may occur due to social and religious norms in Oman, potentially influencing the precision of certain associations. Finally, although selecting controls from the same clinical setting ensured that both cases and controls underwent similar diagnostic procedures, which may reduce differential misclassification and improve comparability, potential selection bias cannot be ruled out, as hospital-based controls undergoing colonoscopy may not fully represent the underlying population.
Although patients were recruited from the two largest tertiary referral hospitals in Oman, which receive referrals from all regions of the country, the study population may represent a selected referral cohort rather than the broader community CRC population. Tertiary centres may disproportionately receive younger patients, individuals with IBD, complex clinical presentations or patients requiring specialised management. This referral pattern may partly explain the relatively high proportion of younger patients and IBD observed in our cohort and may affect the generalisability and magnitude of observed associations. Therefore, findings should be interpreted within the context of a hospital-based tertiary-care population.
Future population-based and multicentre studies involving primary, secondary and community settings are needed to confirm these findings.
Conclusions
This multicentre case–control study conducted in Oman examines both modifiable and non-modifiable risk factors among patients diagnosed with CRC, providing preliminary evidence to inform national prevention and screening strategies. The study demonstrates that CRC is strongly associated with multiple risk factors, including smoking, elevated BMI, diabetes mellitus, hypertension, family history of CRC, IBD and colorectal polyps. Among these, smoking and hypertension show the strongest independent associations after adjustment for confounders.
These findings highlight the critical role of lifestyle and metabolic factors in the development of CRC and underscore the need for targeted prevention strategies, risk-based screening and early surveillance, particularly among high-risk groups in Oman. Furthermore, integrating smoking cessation, weight management and optimal control of chronic diseases into national CRC prevention and screening programmes may substantially reduce the burden of CRC. Future longitudinal and mechanistic studies are warranted to further elucidate causal pathways and confirm these associations in broader populations.
Supplementary material
Acknowledgements
The authors gratefully acknowledge Dr Nuha El Sharif and Dr Issa Ghrouz, Associate Professors of Medical Science/Epidemiology at Al-Quds University, Palestine, for granting permission to adapt the CFRC Risk Factor Questionnaire for use in the present study.16 They also extend their sincere gratitude to the study participants for their cooperation and valuable contributions to the success of this research.
Footnotes
Funding: This work was supported by a strategic grant from His Majesty’s Trust Fund (grant number #SR/MED/FMCO/23/01).
Prepublication history and additional supplemental material for this paper are available online. To view these files, please visit the journal online (https://doi.org/10.1136/bmjopen-2026-117673).
Provenance and peer review: Not commissioned; externally peer reviewed.
Patient consent for publication: Consent obtained directly from patient(s).
Ethics approval: This study involved human participants and participation was voluntary. The confidentiality of all collected data was assured. Ethical approval was obtained from the institutional research ethics committees of SQUH (approval #SQU-EC/251/2023, MREC #3239, dated 7 March 2024) and RH (approval #MoH/DGPS/CSR/PROPOSAL_APPROVED/4/2024, dated 1 August 2024). All study procedures were performed in accordance with good clinical practice and the principles of the revised Declaration of Helsinki. Written informed consent was obtained from all participants following a detailed explanation of the study and their right to decline participation.
Patient and public involvement: Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Data availability statement
Data are available on reasonable request.
References
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