Diverging Temporal Trends in Stroke Incidence in Younger vs Older People: A Systematic Review and Meta-analysis

Abstract

Importance: Overall stroke incidence is falling in high-income countries, but data on time trends in incidence of young stroke (ie, stroke in individuals younger than 55 years) are conflicting. An age-specific divergence in incidence, with less favorable trends at younger vs older ages, might be a more consistent underlying finding across studies.

Objective: To compare temporal trends in incidence of stroke at younger vs older ages in high-income countries.

Data sources: PubMed and EMBASE were searched from inception to February 2022. One additional population-based study (Oxford Vascular Study) was also included.

Study selection: Studies reporting age-specific stroke incidence in high-income countries at more than 1 time point.

Data extraction and synthesis: For all retrieved studies, 2 authors independently reviewed the full text against the inclusion criteria to establish their eligibility. Meta-analysis was performed with the inverse variance-weighted random-effects model. Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline was followed.

Main outcomes and measures: The main outcome was age-specific divergence (<55 vs ≥55 years) in temporal trends in stroke incidence (relative temporal rate ratio [RTTR]) in studies extending to at least 2000. RTTRs were calculated for each study and pooled by random-effects meta-analysis, with stratification by administrative vs prospective population-based methodology, sex, stroke subtype (ischemic vs intracerebral hemorrhage vs subarachnoid hemorrhage) and geographical region.

Results: Among 50 studies in 20 countries, 26 (13 prospective population-based and 13 administrative studies) reported data allowing calculation of the RTTR for stroke incidence at younger vs older ages across 2 or more periods, the latest extending beyond 2000. Reported trends in absolute incidence of young individuals with stroke were heterogeneous, but all studies showed a less favorable trend in incidence at younger vs older ages (pooled RTTR = 1.57 [95% CI, 1.42-1.74]). The overall RTTR was consistent by stroke subtype (ischemic, 1.62 [95% CI, 1.44-1.83]; intracerebral hemorrhage, 1.32 [95% CI, 0.91-1.92]; subarachnoid hemorrhage, 1.54 [95% CI, 1.00-2.35]); and by sex (men, 1.46 [95% CI, 1.34-1.60]; women, 1.41 [95% CI, 1.28-1.55]) but was greater in studies reporting trends solely after 2000 (1.51 [95% CI, 1.30-1.70]) vs solely before (1.18 [95% CI, 1.12-1.24]) and was highest in population-based studies in which the most recent reported period of ascertainment started after 2010 (1.87 [95% CI, 1.55-2.27]).

Conclusions and relevance: Temporal trends in stroke incidence are diverging by age in high-income countries, with less favorable trends at younger vs older ages, highlighting the urgent need to better understand etiology and prevention of stroke at younger ages.

Figure 1.. Temporal Trends in Population- and Administrative-Based Studies in Stroke Incidence at Younger Ages and in the Ratio of Incidence at Younger Ages/Incidence at Older Ages

A, Results of individual studies reporting stroke or ischemic stroke (IS) incidence rates at younger ages beyond 2000 stratified by study methodology (population- vs administrative-based studies). One study reporting incident rates in individuals aged 45 to 59 years could not be plotted on the same scale. Full age-specific results are reported in eFigure 5 in the Supplement where full details of age bands and stroke subtypes of all individual studies are provided. B, Change in the ratio of young-age vs old-age stroke over time within individual studies providing age-specific stroke or ischemic stroke incidence rates over time stratified by study methodology (population- vs administrative-based studies). Not all of the studies in panel A are included in panel B, as some did not report incidence rates at older ages (eFigure 4 in the Supplement). Young age includes any individuals younger than 60 years, with the majority reporting younger than 55 years. TIA indicates transient ischemic attack.

Figure 2.. Meta-analysis of the Relative Stroke Incidence Change Over Time at Younger vs Older Ages

Relative temporal trend ratios (RTTRs) for each study were pooled with inverse variance–weighted random-effects meta-analysis to generate a pooled RTTR with 95% CI. This analysis included studies reporting all stroke/ischemic stroke (IS) with an age comparison of younger than 55 years vs 55 years or older where possible, stratified study method (population- vs administrative-based data) and by recency of latest time period (2000-2010 vs after 2010). RTTRs were calculated by dividing the temporal incidence rate ratio within each study in the younger age group (where possible, <55 years) by the incidence rate ratio of the older age group.

Figure 3.. Pooled Estimates of the Relative Stroke Incidence Change Over Time at Younger vs Older Ages Stratified According to Clinical or Study Characteristics

Relative temporal trend ratios (RTTRs) for each study were pooled with inverse variance–weighted random-effects meta-analysis to generate a pooled RTTR with 95% CIs. Details of each subgroup analysis are presented in eFigure 7 in the Supplement. CVD indicates cerebrovascular disease; ICH, intracerebral hemorrhage; SAH, subarachnoid hemorrhage. ^aLimited to studies that reported data within 3 years of a decade boundary in 2 consecutive decades.