Temporal trends in stroke incidence in young people: a systematic review of population based studies.

The problem

Over the past four decades there has been about a 40% reduction in stroke incidence in high-income countries. (Feigin 2009) However, there is anecdotal evidence that this reduction has not occurred in younger age groups. The primary objective of this review is to ascertain whether there is more reliable evidence of an increase in incidence of stroke in young people (<60 years) in high income countries over the last four decades.

The approach

We searched for studies meeting the following eligibility criteria: i. Studies of stroke incidence ii. conducted in high income settings iii. reporting incidence or raw numbers sufficient to calculate incidence in populations under 60 years, iv. data collection over a period of several years (continuously or periodically) in one and the same catchment area. Age standardised incidence with corresponding 95% CI was plotted for each study to facilitate comparisons.Information sources: Pubmed, Medline, Cochrane library, Centre for Reviews and Dissemination, and Google were systematically searched to February 2015. Additional studies were identified by contacting clinical experts and searching bibliographies and abstracts.

Findings

Population-based studies in high income countries show a consistent pattern of an increasing incidence of stroke at age <60 years over the last few decades, whereas incidence has declined in older age groups. Pooled analyses show that these trends are statistically significant and are robust to assumptions about various temporal diagnostic and ascertainment biases.

Consequences

Stroke incidence at younger ages does appear to have been increasing in high-income countries. There is an urgent need for further studies to assess temporal trends in incidence, case-fatality, severity, and risk factors and to understand the age-specific heterogeneity in trends.

Credits

• Catherine Scott
• Linxin Li
• Peter Rothwell