The impact of multimorbidity and sociodemographic factors on cost-related medication nonadherence

Access to prescription medications is a key determinant of chronic disease management and outcomes, yet cost can be a major barrier.

This study aimed to quantify cost-related medication nonadherence (CRMNA) and determine how CRMNA varied by sociodemographic and health factors.

The 2021, 2022, and 2023 adult samples of the National Health Interview Survey were used. CRMNA was self-reported and defined at 3 intensity levels: high, some, and low. Sociodemographic and health factors included age, race, education, income, multimorbidity, and geography. Chi-square tests were used to assess CRMNA differences by key sociodemographic and health factors, and a cumulative logit model was used to evaluate associations between sociodemographic and health factors and CRMNA levels.

From 2021 to 2023, the prevalence of any CRMNA increased from 9.62% to 10.76%. In multivariable models, each additional chronic disease medication was associated with 36% higher odds of experiencing a greater level of CRMNA (adjusted odds ratio [aOR] 1.36 [95% CI 1.30-1.42], P < 0.0001). Adults of 2 or more races had higher odds of CRMNA than non-Hispanic white adults (aOR 1.59 [95% CI 1.22-2.08], P = 0.0007). Compared with adults aged 18-24 years, adults aged 25-34 years had the highest odds of CRMNA (aOR 1.76 [95% CI 1.37-2.28], P < 0.0001), whereas adults aged 65 years and older had the lowest (aOR 0.53 [95% CI 0.41-0.67], P < 0.0001). Compared with privately insured individuals, those with public insurance had 21% lower odds of CRMNA (aOR 0.79 [95% CI 0.70-0.90], P = 0.0004), whereas uninsured individuals had more than twice the odds (aOR 2.58 [95% CI 2.16-3.09], P < 0.0001).

This study highlights the disproportionate burden of CRMNA among racial minorities and multimorbid privately insured young adults. These groups are most vulnerable to the cumulative costs of chronic disease medications and may thus require clinical and policy strategies to minimize cost burden and improve adherence.