Cognitive impairment and medication adherence in stroke

Aim

The overarching aim of this thesis was to explore the bidirectional association between adherence to secondary prevention medications and cognitive impairment in stroke survivors. A secondary aim was to provide an updated account of the longer-term outcomes of cognitive impairment post-stroke.

Methods and results

Five interrelated studies were conducted to address these aims. Study 1 explored the association between cognitive impairment and cardiovascular medication use in an Irish sample of the general population aged 50+, finding no evidence of an independent association between use of cardiovascular medications and cognitive impairment. Study 2 systematically reviewed the existing literature on the association between cognitive impairment and medication adherence in stroke survivors, and found no significant association when all included studies were pooled, although heterogeneity was significant and the overall evidence quality poor. Studies 3, 4 and 5 were based on a 5-year follow-up of the Action on Secondary Prevention Interventions and Rehabilitation in Stroke (ASPIRE-S) cohort study. Study 3 explored the impact of cognitive impairment on subsequent medication adherence, as well as the impact of medication non-adherence on later cognitive impairment. While this study found no statistically significant associations between cognitive impairment and medication adherence, stroke survivors with cognitive impairment were significantly more likely to receive help with medication taking. Study 4 considered the impact of cognitive impairment on outcomes, finding that cognitive impairment at 6 months post-stroke was associated with significantly increased risk of mortality, further cognitive decline, worse quality of life, lower levels of independence, and increased likelihood of depressive symptoms at 5 years. Study 5 explored family caregiver psychological wellbeing, and revealed that family caregivers of stroke survivors with cognitive decline were significantly more likely to experience anxiety and depression.

Conclusion

Taken together, the findings from this thesis do not indicate an association between cognitive impairment and medication adherence in stroke survivors. However, a number of factors could account for this lack of consistent association, including the moderating effect of help received with medication taking, as well as the range of definitions and assessments of non-adherence and cognitive function, which make it difficult to draw comparisons across studies. Given the prevalence of both of these phenomena in stroke survivors, and their associations with poorer outcomes, the design of effective interventions to address medication non-adherence and to reduce the burden of cognitive impairment post-stroke is paramount.