Trends in Stroke Incidence in High-Income Countries in the 21st Century

Population-Based Study and Systematic Review

Linxin Li, DPhil; Catherine A. Scott, BMBCh; Peter M. Rothwell, FMedSci

Disclosures

Stroke. 2020;51(5):1372-1380. 

In This Article

Results

Based on 2811 incident stroke cases in OCSP (n=557) and OXVASC (n=2254), stroke incidence fell by 32% from 1981 to 1986 to 2014 to 2017 (IRR, 0.68 [95% CI, 0.60–0.78]; P<0.0001), with no evidence of heterogeneity before and after the year 2000 (P het=0.54; OXVASC 2002–2005 versus OCSP 1981–1986: 0.80 [95% CI, 0.70–0.91]; P=0.0006), and after (2014–2017 versus 2002–2005: 0.85 [95% CI, 0.74–0.98]; P=0.03).

Using the above estimates, we applied different scenarios for the projection of the number of first-ever stroke patients in the United Kingdom between 2015 and 2045. The UK population is projected to increase by 3.6 million (5.5%) over the next 10 years and reaching 72.9 million in mid-2041 with doubling number of individuals aged ≥85 years.[26] If the age-specific incidence remained stable over the next 30 years, the number of incident stroke would increase by 66% from year 2015 to 2045. If the age-specific stroke incidence continued to decline with its current magnitude (OXVASC estimates: 6% every 5 years), there would be a 13% increase of the number of first-ever strokes in the United Kingdom up to year 2045. To maintain a stable number of incident stroke patients in the United Kingdom in 2050, the incidence would have to decrease by 8% every 5 years.

Sixteen thousand six hundred thirty-eight citations were identified, and 13 population-based studies from 9 high-income countries were included in the systematic review (Figure I and References in the Data Supplement).[11–16,19,27–29,30–31] Of the 13 studies, 9 (including unpublished data from OXVASC)[11–19,29–31] reported temporal trends of stroke incidence including at least 1 period after year 2010 and were thus included in the main analysis (Table 1). An additional 4 studies reporting either temporal trends between 1990 and 2000 or after year 2000 were also included in the sensitivity analysis (Table I in the Data Supplement). No published study reported change of stroke incidence beyond year 2010.

Combining results from Oxfordshire and the systematic review, 31 351 new stroke cases occurred during ≈18 453 235 person-years of observation. Despite noticeable variation in absolute age-standardized stroke IRs between studies, stroke incidence declined significantly between the 1990s and 2010s in all studies (Table 1; Table I in the Data Supplement), resulting in less between-study difference in absolute rates after year 2010 (highest versus lowest incidence before year 2000: 183 versus 81 per 100 000 population; after year 2010: 143 versus 98 per 100 000 population).

Although the rates of reduction in stroke incidence varied slightly between studies, the trend of steady decline was consistent across studies (Figure 1). Consequently, the pooled estimate from the 9 studies between 1990s and 2010s suggested a 28% decline of stroke incidence during an average study duration of 16.5 years (IRR, 0.72 [95% CI, 0.66–0.79]; P<0.0001; Figure 2), with no differences between men and women (8 studies; Pdifference=0.56; Table 2). The results were also largely consistent by stroke subtypes (Table 2). Sensitivity analyses excluding the 4 studies with the longest study duration (Oxfordshire, Sweden,[17,18,32,33] and Auckland[11,12]) also showed consistent results (mean study duration, 12 years; IRR, 0.78 [95% CI, 0.70–0.86]; P<0.0001).

Figure 1.

Temporal trends of standardized stroke incidence in population-based studies reporting at least 1 time point after year 2010 (1990–2010).

Figure 2.

Meta-analysis (random effects) of standardized incidence rate ratio (IRR; temporal trend) in population-based studies of first-ever stroke (1990–2010). †Raw numbers of incident stroke cases for each study for the 2 time periods included are presented in Table 1.

Two studies of similar duration (Oxfordshire and Porto[13]) reported the temporal trends of stroke incidence stratified by stroke severity (Figure 3). In contrast to a 30% reduction of disabling or fatal stroke during a mean study duration of 11.5 years, there was no statistically significant reduction in nondisabling stroke (pooled IRR, 0.98 [95% CI, 0.85–1.12]; P=0.73; Figure 3) due apparently to reductions in the proportion of disabling or fatal stroke (2 studies; early versus later period, 53.6% versus 46.1%; odds ratio, 0.77 [95% CI, 0.62–0.96]; P=0.02; Figure 3).

Figure 3.

Meta-analysis (random effects) of standardized incidence rate ratio (IRR; temporal trend) in population-based studies of first-ever stroke stratified by stroke severity. A, Change of the proportions of disabling or fatal stroke. B, Change of IRR. OR indicates odds ratio. †Raw numbers of incident stroke cases for each study for the 2 time periods included can be derived from A.

In the subgroup analysis stratified by study periods, although more heterogeneity was observed post-year 2000 (Figure II in the Data Supplement), the pooled estimates for the reduction of stroke incidence in each period were consistent (1990–2000: 9 studies; mean study duration, 9 years; IRR, 0.84 [95% CI, 0.74–0.94]; P=0.003 versus post-year 2000: 11 studies; mean study duration, 10 years; IRR, 0.82 [95% CI, 0.73–0.93]; P=0.001; Figure II in the Data Supplement) and were maintained after year 2010 in OXVASC (Figure 1). There was also no difference in the trends between men and women within each period (P difference=0.22 for 1990–2000 and P difference=0.73 post-year 2000; Table 2). Again, results were also largely comparable for ischemic versus hamorrhagic strokes, although the reduction of subarachnoid hemorrhage was more marked post-year 2000 (Table 2), whereas the reduction of intracerebral hemorrhage became less marked in more recent periods (Table 2).

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