Kathryn S. Hayward,
Stroke incidence has been decreasing over time. It is acknowledged that a reduction is occurring in older adults (age >65 years), but trends in younger adults remain less clear. Long-term cohort studies, such as the Framingham Study, provide the opportunity to characterize trends in rates of ischemic stroke. Such work can inform prevention efforts, both nationally and internationally.
In this paper, Aparicio and colleagues report on the trends in 10-year incidence of ischaemic stroke among participants of the Framingham Heart Study. They divided participants into 35 to 54 years of age (younger adults) and ≥55 years of age (older adults). Individuals that attended exams at the Study clinic during four epochs from 1962 through 2005 were included.
In both age groups, prevalence of smoking, hypertension and cholesterol declined across epochs, whereas prevalence of obesity increased across epochs. Prevalent atrial fibrillation increased in the older age group only. The long-term decline in cardiovascular risk factors emphasizes the importance of developing targeted, early prevention approaches to support continued declines.
Seventy-one (0.6%) cases of ischaemic stroke were observed in younger adults, while 620 (5.4%) cases were observed in the older adults. The 10-year age-adjusted and sex-adjusted cumulative incidence of ischaemic stroke declined over time in both age groups. The decline was greater in the older group as compared to the younger group (older incidence declined by 24%, 41% and 53%; younger incidence declined by 11%, 34%, 39%). Testing for trends across the four epochs, the decline was significant over time in the older group (HR trend 0.82, 95% CI 0.77-0.88; p<0.001), but was not significant in the younger group (HR trend 0.87, 95% CI 0.74-1.02; p=0.09).
The current findings from a community sample contribute new data to the conflicting evidence base surrounding rates of stroke in younger adults. The authors discuss previous reports which have suggested both decreases and increases in midlife strokes. Given the low rate of midlife stroke in the Framingham Study (<1%), it would be interesting to examine a similar question in a cohort with the potential to demonstrate higher rates of midlife stroke, i.e., higher cardiovascular risk factor presence. Further, the authors acknowledge the limitation of ancestry, suggesting evaluation of more ancestrally diverse cohorts could enhance generalizability.