Understanding gender differences in statin use among elderly Medicare beneficiaries: an application of decomposition technique.

BACKGROUND: Pharmacotherapy with statins (HMG-CoA reductase inhibitors) is the cornerstone for lipid management in individuals with or at risk of developing cardiovascular diseases. Although the clinical benefits of statins are established for both women and men, there is evidence of a gender difference in their use. The current study extends prior scientific research by estimating the extent to which individual-level variables may explain gender differences in statin use by using a post-regression non-linear decomposition technique.
OBJECTIVE: The objective of this study was to estimate the magnitude of gender differences in statin use among the elderly and examine individual-level variables that can explain the gender differences in statin use among elderly individuals with or at risk of cardiovascular diseases.
METHODS: A retrospective cross-sectional study design was adopted. Data were derived from the 2005 Medicare Current Beneficiary Survey (MCBS), a nationally representative survey of Medicare beneficiaries in the US. The analytic study sample consisted of community-dwelling elderly Medicare beneficiaries, aged 65 years or older, who had reported any of the following conditions: heart disease, hyperlipidaemia or diabetes mellitus, and who were alive during the observation year. Chi-square tests were used to evaluate the unadjusted associations between gender and statin use for each of the characteristics. Multivariate logistic regressions were used to evaluate the relationship between gender and statin use. A post-regression non-linear decomposition approach was used to understand individual-level variables that could explain gender differences in statin use.
RESULTS: Among 5,508 elderly, 47.2% of the women and 55.5% of the men reported any statin use in 2005, which translates to an 8.3 percentage point difference in statin use. In the multivariate logistic regression on statin use, women were 21% less likely than men to use statins (adjusted odds ratio = 0.79; 95% CI 0.69, 0.89). Post-regression non-linear decomposition analysis revealed that of the 8.3 percentage point difference in statin use, 29.5% was explained by the individual-level variables. Lifestyle risk factors accounted for most of the explained portion of the gender difference in statin use.
CONCLUSIONS: Among elderly Medicare beneficiaries, women were less likely than men to report any use of statins. Less than one third of the total gender difference in statin use was attributed to individual-level variables such as demographics, economic status, physical health status, depression and lifestyle risk factors. Further research is needed to identify whether provider and/or organizational-level factors can further explain the gender difference in statin use.