Adherence to calcium/vitamin D and estrogen protocols among diverse older participants enrolled in a clinical trial.

Purpose: This study was intended to identify characteristics of those who adhere poorly to calcium/vitamin D and estrogen replacement protocols, and aimed to assess the effects of ethnicity, socio-economic status, and health status on medication adherence.

Methods: The adherence rates of 107 older white, African American and Hispanic participants of a clinical trial involving calcium/vitamin D and either estrogen replacement or placebo therapy were analyzed. Structural equation modeling was used to test the hypothesis that minority participants would have lower adherence rates than white participants, but only if they had lower household incomes and educational achievement, more osteoporosis risk factors, negative health assessments, and fewer somatic complaints than white participants.

Results: The average age of participants was 76 years. Minority participants and those with lower SES had lower adherence rates than white participants and those with higher SES. Plausible models that met goodness-of-fit criteria showed that the estrogen/placebo adherence rates were affected directly by being African American or Hispanic and the SF-36 mental health score, and indirectly by somatic complaints. History of fracture and household income directly predicted calcium/vitamin D adherence rates.

Conclusion: Efforts to improve adherence to medical regimens should consider differences in adherence behaviors based on ethnicity, SES, and mental health.