Does Marital Status Affect Cancer Risk?

Adults who have never been married had a higher cancer risk than their married or previously married peers, with patterns observed across many major cancer types and particularly strong for cancers linked to infections, smoking, and reproductive factors, new data suggest. The findings are based on a large, population-based cancer registry analysis of more than 4 million cases, making it the largest study of its kind in the US. First author Paulo Pinheiro, PhD, cautioned, however, that the study does not suggest that marriage itself is protective. "As with any observational study, we cannot establish causation, and unmeasured factors may contribute to the associations,” said Pinheiro, with Sylvester Comprehensive Cancer Center, University of Miami Health System, in Miami. Marital status may, however, help identify groups with different patterns of cancer risk, which likely reflect social and lifestyle behaviors rather than a direct causal effect, Pinheiro explained. Married individuals, for instance, are less likely to smoke — a known cancer risk factor — and more likely to have children and undergo cancer screening, which can influence cancer incidence through reproductive effects and screening, including earlier detection and removal of precancerous lesions. "Marital status is therefore best understood as a marker of those accumulated factors," Pinheiro said. The study was published online on April 8 in Cancer Research Communications. Filling a Data Gap Marriage has consistently been associated with earlier cancer diagnosis and improved survival among those with cancer, but its relationship to cancer incidence remains less clear. To address that gap, researchers analyzed data from 12 US states that included demographic and cancer information for more than 4.2 million cancer cases diagnosed between 2015 and 2022. The analysis included more than 500 million person-years at risk in adults 30 years or older, representing an annual population of more than 62 million. The never-married group comprised about 19% of the total population — 22% were men and 17% were women. Compared with ever-married individuals, never-married men and women had higher cancer incidence across many major cancer types, racial and ethnic groups, and age groups. Overall, cancer rates were about 68% higher in never-married men and 85% higher in never-married women compared with their ever-married counterparts (incidence rate ratios [IRRs], 1.68 and 1.85, respectively). Never-married Black men had the highest overall cancer rates (1600 per 100,000), whereas married Black men had significantly lower rates than married White men (752.6 vs 836.2 per 100,000), suggesting complex interactions between marital status and structural factors, the researchers noted. Site-specific patterns revealed clues to potential mechanisms linking marital status and cancer. Compared with ever-married individuals, never-married people had the highest excess risks for human papillomavirus-related cancers — about five times higher for anal cancer in men (IRR, 5.04) and approaching three times higher for cervical cancer in women (IRR, 2.64). Other strong associations between never-married individuals and cancer risk were observed for smoking-related cancers, including lung (IRR, 2.1 for both men and women) and esophageal cancers (IRR, 2.4 in men and 2.7 in women), and malignancies including liver (IRR, 2.3 for both men and women), bladder (IRR, 2.3 women only), and colorectal (IRR, 2.1 women only) cancers. Among women, the higher incidence of ovarian and uterine cancers (IRR, 2.4 for both) among the never-married group supports the influence of reproductive mechanisms, such as giving birth, on cancer risk. The association between marital status and cancer risk was weaker for breast, prostate, and thyroid cancers (with IRRs 2), suggesting potentially less modifiable etiologies. Overall, “methodologically, it is quite robust, particularly in its clear framing of ever- vs never-married individuals and the use of standardized incidence rates and regression modeling,” Pinheiro said. The analysis did not adjust for individual-level risk factors such as smoking, diet, physical activity, or alcohol use — factors that may partly explain the observed associations. Adjusting for these lifestyle and health behavior factors at the individual level would require detailed information on these behaviors, and “data at that level simply do not exist at a national scale,” Pinheiro said. It would also “obscure the real-world pattern we are trying to measure.” Gilbert Welch, MD, noted that adjusting for these individual-level cancer risk factors “would certainly attenuate the associations.” “That said, it wouldn’t be crazy to suggest marriage drives some of these risk factors,” said Welch, general internist and senior investigator at the Center for Surgery and Public Health, Brigham and Women’s Hospital, Boston. Married couples benefit from combined incomes and shared expenses, and “may well help support individuals in making healthy choices (like not smoking).” But, he added, “it would be crazy to suggest that the reason to get married is to lower cancer risk.” The authors flagged a study limitation — the fact that ever-married status lumps together people who are currently married, divorced, and widowed, and these groups may have different risk profiles. Additionally, “individuals in strained or abusive marriages may not experience protective social benefits,” while those in long-term cohabiting relationships classified as never-married may experience high levels of support, the authors wrote. Overall, though, Pinheiro clarified that the main finding is “not about marriage as a causal agent, but about identifying a large population group, the never-married, with a consistently higher cancer burden that has been largely overlooked in public health practice and cancer prevention efforts.” Linda Waite, professor, Department of Sociology, University of Chicago, who wasn’t involved in the study, wasn’t surprised by the findings. For men, not having a spouse may “disadvantage” them in ways that might increase cancer risk. Unmarried men are more likely to drink and smoke heavily, which increase cancer risk, she said. A spouse may also influence health awareness and decisions, such as noticing suspicious symptoms, pushing their partner to see a doctor, or helping manage their partner’s care. Plus, “for both men and women, having a spouse may improve medical care by giving each partner a companion for medical appointments and another person to help manage risks of disease,” Waite said. The study had no commercial funding. Pinheiro and Waite had no relevant disclosures.