We identified 25 535 people who retired between 1996 and 2010, 21 052 of whom were alive at least 1 year after their retirement and were included in our analyses. Complete prescription data were available for all included participants.
Of the 21 052 participants, 3889 had hypertension before their retirement, and 611 had type 2 diabetes before their retirement. We only included patients with hypertension (n = 3468) or type 2 diabetes (n = 412) whose diagnoses were made before the start of our observation period; thus, we excluded 421 patients with hypertension and 199 patients with diabetes whose diagnoses were made after the start of our observation period.
Of the 3880 included participants, 2720 (70.1%) were female, corresponding the sex distribution of the overall cohort (). Median age at retirement for participants was 61 years (interquartile range 55–64 yr). The mean follow-up was 6.8 years for patients with hypertension and 6.7 years for patients with diabetes.
Baseline characteristics of the study population
Among men with hypertension, the adjusted prevalence of poor adherence to antihypertensive medication was 5.6% during the 3 years of follow-up before their retirement and 7.2% during the 4 years of follow-up after their retirement (). The corresponding adjusted OR was 1.32 (95% CI 1.03–1.68, postretirement v. preretirement). We saw a similar trend in relation to antidiabetic medication: the adjusted prevalence of poor adherence was 2.3% before retirement and 5.2% after retirement, with an adjusted OR of 2.40 (95% CI 1.37–4.20). Among women, the ratio for poor adherence to antihypertensive medication was 1.25 (95% CI 1.07–1.46), with a preretirement prevalence of poor adherence of 6.1% and a postretirement prevalence of 7.5%. We saw no significant change in adherence in relation to antidiabetic medication for women before and after retirement.
Rates of poor medication adherence among study participants before and after retirement
More-detailed year-by-year trajectories of poor medication adherence, adjusted for age at retirement and calendar year, confirmed that the annual prevalence of poor adherence to antihypertensive medication was higher for each year of postretirement follow-up than for preretirement follow-up (Appendix 3, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.122012/-/DC1
). For men, but not women, a similar pattern was seen for annual prevalences of poor adherence to antidiabetic medication.
Among men, we saw a postretirement increase in prevalence of poor adherence to antihypertensive and antidiabetic medications in younger and older employees, across occupational groups, sizes of residence and types of retirement, and among those with and without comorbidity ( and Appendix 4, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.122012/-/DC1
). The results for women with hypertension were similar ( and Appendix 4), with the exception that poor adherence did not increase substantially after retirement among those with comorbid cardiovascular conditions. Nonetheless, there was no statistical evidence to suggest that the postretirement increase in poor adherence would differ between subgroups (all p
for interaction > 0.07).
Prevalence of poor adherence to medication among men before and after retirement, by patient subgroup and type of drug. CVD = cardiovascular disease.
Prevalence of poor adherence to antihypertensive medication among women before and after retirement, by patient subgroup. CVD = cardiovascular disease.
Repeating our main analysis using alternative cut-offs for poor adherence showed postretirement increases in poor adherence among men and women with hypertension for all alternative definitions, ranging from less than 20% of days to less than 80% of days covered by treatment. For example, when poor adherence was defined as less than 80% of days covered by filled prescriptions, adherence was 19.9% before retirement and 24.1% after retirement for men with hypertension (adjusted OR 1.29, 95% CI 1.11–1.49) (). A postretirement increase in poor adherence was also seen in men with type 2 diabetes when poor adherence was defined as less than 20%, 30%, 40% or 50% of days covered by treatment.
Prevalence of poor medication adherence before and after retirement using alternative definitions of poor adherence