Decreasing rates of cost-related medication non-adherence by age advancement among American generational cohorts 2004-2014: a longitudinal study

Objectives The access barrier to medication has been a persistent and elusive challenge in the US healthcare system and around the globe. Cost-related medication non-adherence (CRN) is an important measure of medication non-adherence behaviours that aim to avoid costs. Longitudinal study of CRN behaviours for the ageing population is rare. Design Longitudinal study using the Health and Retirement Study to evaluate self-reported CRN biennially. Setting General population of older Americans. Participants Three cohorts of Americans aged between 50 and 54 (baby boomers), 65-69 (the silent generation) and 80 or above (the greatest generation) in 2004 who were followed to 2014. Intervention Observational with no intervention. Primary and secondary outcome measures Longitudinal CRN rates for three generational cohorts from 2004 to 2014. Population-averaged effects of a broad set of variables including sociodemographics, income, insurance status, limitations in activities of daily living (ADLs) and instrumental activities of daily living (IADLs), and comorbid conditions on CRN were derived using generalised estimating equation by taking into account repeated measurements of CRN over time for the three cohorts, respectively. Results The three cohorts of baby boomer, the silent generation and the greatest generation with 1925, 2839 and 2666 respondents represented 12.3 million, 8.2 million and 7.7 million people in 2004, respectively. Increasing age was associated with decreasing likelihood of reporting CRN in all three generational cohorts (p<0.05), controlling for demographics, income, insurance status, functional status and comorbid conditions. All three generational cohorts had a higher prevalence of diabetes, cancer, heart conditions, stroke, a higher percentage of respondents with Medicare-Medicaid dual eligibility and lower percentage with private insurance in 2014 compared with 2004 (p<0.05). Conclusion The paradox of decreasing CRN rates, independent of disease burden, income and insurance status, suggests populations' CRN behaviours change as Americans age, bearing implications to social policy.