Prevalence and Demographic Correlates of Multimorbidity in Adults Seen by Primary Care Physicians

Background: Multimorbidity, defined as the presence of two or more chronic conditions, is increasingly common in primary care and poses challenges for both clinical management and health policy. Understanding the demographic predictors of multimorbidity is critical for guiding resource allocation and improving patient care. Objective: To estimate the proportion of adult primary care visits involving patients with ≥2 chronic conditions and identify demographic predictors using nationally representative data from the National Ambulatory Medical Care Survey (NAMCS) 2010–2015. Methods: This cross-sectional analysis included 29,879 unweighted adult visits, representing 897,485,008 weighted visits to family physicians. Multimorbidity was defined as ≥2 chronic conditions. Survey-weighted descriptive statistics and multivariable logistic regression assessed associations with age, sex, insurance type, and race/ethnicity. Results: Multimorbidity accounted for 412,455,652 (46%) of visits. Patients with multimorbidity were older (mean 61.8 vs. 45.9 years, p < 0.001). Males had a slightly higher prevalence than females 183,212,644 (49%) vs. 229,243,008 (44%), though women accounted for more total visits. Insurance type showed significant differences: Medicare 1,156,366 (17%) had the lowest multimorbidity proportion, while Medicaid/CHIP 10,143,624 (25%) and Self-pay/Other 7,077,309 (36%) showed higher proportions. Private insurance accounted for the largest absolute number of multimorbidity visits, 30,067,932 (40%). Non-Hispanic Black patients had higher odds (aOR 1.47, 95% CI 1.21–1.77). Conclusion: Multimorbidity is common in U.S. primary care, particularly among older adults and socioeconomically vulnerable groups. Targeted clinical and policy strategies are needed to reduce disparities and improve management of multimorbidity in family practice.