The risk of vascular dementia, but not Alzheimer’s disease, is higher in post-MI patients
Higher Risk of Vascular Dementia in Myocardial Infarction SurvivorsSundbøll J, Horváth-Puhó E, Adelborg K, et al. - Circulation 2017; published online ahead of print
MI has been associated with ischemic and hemorrhagic stroke, which, in turn, increase the risk of dementia, however, available data about the association between MI and dementia are scarce and showed conflicting results [1,2]. The possible mechanisms leading to post-MI stroke and dementia include brain hypoperfusion due to lower EF and BP, or due to CABG, and MI-complications, such as AF that leads to thrombus formation . MI and dementia also share common risk factors, such DM, hypercholesterolemia, hypertension and atherosclerosis.
In this study, the long-term risk of dementia (Alzheimer’s disease, vascular dementia and other dementias) following first-time MI was investigated. Moreover, the impact of MI-complications and post-MI- treatments on dementia risk was evaluated. All patients with a first-time MI during the study period from 1 January 1980 to 1 September 2012 were identified in the Danish National Patient Registry (DNPR), and a general population comparison cohort was created using the Danish Civil Registration System [4,5]. For each patient in the MI cohort, 5 individuals from the general population without an MI diagnosis were randomly selected and matched by gender, age, and calendar year of MI diagnosis. Individuals in the general population cohort with a MI after the index date, were transferred to the MI cohort. All MI patients and members of the general population cohort were followed until the occurrence of any dementia diagnosis, emigration, death, or 31 December 2014, whichever came first.
Individuals with a history of dementia, mild cognitive impairment, or an amnestic syndrome at baseline were excluded from the analysis, in order to identify only the incident dementia cases. Diagnoses of dementia during the first year after MI were not taken into account, since they are unlikely to be a consequence of MI.
- 314,911 patients with a first-time MI were followed-up for a median of 7.7 years (25th–75th percentile: 4.0–13.1 years), and 1,573,193 matched individuals from the general population were followed-up for a median of 9.8 years (25th–75th percentile: 5.2–16.0 years).
- Over 35 years of follow-up, the cumulative incidence of all-cause dementia in the MI cohort was 8.7% (2.8% for Alzheimer’s disease, 1.6% for vascular dementia, and 4.5% for other dementias).
- There was no association with all-cause dementia (adjusted HR: 1.01; 95% CI: 0.98–1.03) or non-vascular dementia (adjusted HR: 0.98; 95% CI: 0.95–1.01) compared with the general population cohort.
- The risk was somewhat lower for Alzheimer’s disease (adjusted HR: 0.92; 95% CI: 0.88–0.95), whereas the risk of vascular dementia was significantly higher in the MI cohort (adjusted HR: 1.35; 95% CI: 1.28–1.43).
- The incremental risk of vascular dementia was higher in patients who experienced a stroke within 1 year of MI (adjusted HR: 4.48; 95% CI: 3.29–6.12), and atrial fibrillation or flutter were associated with only moderately higher risk (adjusted HR: 1.55; 95% CI: 1.28–1.87).
- The risk of vascular dementia was also higher in patients who underwent pacemaker implantation (adjusted HR: 3.38; 95% CI: 1.42–8.06) or CABG (adjusted HR: 3.99; 95% CI: 1.31–12.18) during their MI admission.
- The incremental risk of vascular dementia was greater with increasing levels of HF severity, measured by the number of HF hospitalizations during the first year after MI (adjusted HR: 2.24; 95% CI: 1.21–4.14 for ≥3 admissions).
Patients with a history of MI have a higher risk of vascular dementia, particularly if they additionally have a history of stroke. There was no association between MI and Alzheimer’s disease or non-vascular dementia. Common risk factors for MI and vascular dementia may be the driving mechanisms explaining the association between the two diseases. Stroke was a strong modifier of this association, without a substantial impact on the association with other dementia subtypes. These data suggest that strategies for the prevention of vascular dementia in post-MI patients are warranted.