A large-scale analysis from the United States associates unmarried status with increased cancer incidence for most cancers, highlighting how social and behavioral factors shape risk across the life course.
Research: Marriage and cancer risk: A contemporary population-based study across demographic groups and cancer types. Image credit: Yuganov Konstantin / Shutterstock
Recent research published in journals cancer research communication suggest that marital status may be associated with differences in cancer risk in the United States. Using population-level data, the researchers found that unmarried adults, especially black men, had significantly higher cancer rates for most cancers.
The risk was 68% higher in men and 83% higher in women compared to married people, and the association was strongest in people aged 55 and older.
Although the findings suggest cumulative behavioral and social effects, some of the observed differences may also reflect marital choices, with important implications for cancer prevention and public health strategies, especially in aging populations and underserved communities.
Background of marriage, social support, and cancer risk
Marriage is associated with improved health outcomes, including longer survival, lower morbidity, and improved self-reported health, primarily due to stronger social support, healthier behavioral habits, and greater financial security. In middle age, unmarried people are also more likely to experience adverse physiological changes characterized by inflammation and metabolic abnormalities.
Married people tend to be diagnosed with cancer earlier and have a more favorable outcome. However, the relationship between marital status and cancer incidence remains unclear.
Existing evidence is limited by outdated, small-scale and region-specific studies that often rely on clinical or medical-based samples and are prone to bias. Furthermore, changing patterns of social norms and risk factors highlight the need for updated population-level research.
US Cancer Incidence Study Design
In this study, researchers evaluated cancer incidence by marital status, cancer site, age, sex, and race/ethnicity. They analyzed data from the Surveillance, Epidemiology, and End Results (SEER) program, which covers 12 U.S. states.
These include Connecticut, California, Hawaii, Georgia, Iowa, Idaho, Louisiana, New Mexico, Kentucky, New Jersey, Utah, and New York. Together, these states will represent approximately 31% of U.S. residents in 2022, including major races and ethnicities.
The study included adults aged 30 and older, and the denominator was obtained from the 2015-2022 American Community Survey (ACS). The research team categorized participants as either married or single. The married group included married people, divorced people, separated people, and widows. Those who were living together or in a partnership outside of a legal marriage were included in the never-married group.
Researchers defined cancer sites using the International Classification of Diseases of Oncology, Third Edition (ICD-O-3) and the World Health Organization (WHO) 2008 classification. Additionally, we determined breast cancer subtypes based on estrogen, progesterone, and human epidermal growth factor receptor 2 (HER2) status. They classified prostate cancer based on prostate-specific antigen (PSA) levels at the time of diagnosis.
Researchers calculated age-specific incidence rates and used regression models to estimate incidence rate ratios (IRRs) comparing unmarried and married adults.
Marital status differences in cancer incidence
SEER data from 2015 to 2022 represents more than 62 million people per year. Overall, 19% were classified as unmarried, with a higher proportion among men (21.5%) than women (17%). Rates varied by race/ethnicity, being highest among black women (34%) and men (35%) and lowest among white women (12%) and men (17%).
During the study period, 4.24 million cases of cancer were diagnosed, 18% of which occurred in unmarried people. The unmarried group consistently had higher incidence rates than married adults, with an IRR of 1.68 for men and 1.85 for women.
Increased risk was observed for most cancer types and demographic groups, with IRRs ranging from 1.62 for white men to 1.96 for black men. Notably, married black men showed lower cancer rates compared to white men in the same married category.
Site-specific analyzes showed the strongest associations with anal, cervical, esophageal, ovarian, uterine, liver, lung, and colorectal cancers (IRR, 2-5). In contrast, smaller differences were observed for thyroid, melanoma, prostate, testicular, kidney, and brain cancers (IRR, 1.2 to 1.6). Screening-sensitive cancers such as prostate cancer (PSA1, IRR, 1.36) and thyroid cancer showed relatively modest associations.
Analysis by age group showed that disparities widened with age, peaking at ages 70 to 74 (IRR 1.99 for men and 2.23 for women). The IRR was higher for adults aged 55 years and older (1.99) than for those aged 30 to 54 years (1.49), suggesting a cumulative life course effect, with women consistently showing higher relative risk than men.
Disparities across racial and ethnic groups were highest for black men (IRR 1.96), followed by Hispanic men (1.82), and white and Asian/Pacific Islander men (both 1.62). In women, the IRR was consistently higher across all groups (1.90–1.94), indicating a similar pattern of increased risk.
Impact of marital status on cancer prevention
The study found that unmarried adults consistently have higher rates of most cancers, especially in later life, and that marital status is an often overlooked social indicator of cancer disparities. Although this finding suggests that marital status reflects cumulative social, behavioral, and medical-related exposures beyond traditional risk factors, legal marital status should not be interpreted as a direct proxy for social support or evidence of causality.
Incorporating marital status into cancer surveillance and risk models may improve identification of high-risk populations and support targeted prevention strategies. Notably, stronger associations with HPV-related cancers, tobacco-related cancers, and reproductive cancers highlight viable pathways for intervention. However, marital status was measured at the time of diagnosis, and the dataset lacked individual-level information on income, education, equality, and health behaviors.
Future research should investigate underlying mechanisms and consider diverse relationship structures beyond legal marriage to better address cancer disparities, which may inform more equitable and socially informed cancer prevention efforts.
