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. 2017 Oct;48(10):2731-2738.
doi: 10.1161/STROKEAHA.117.018187. Epub 2017 Aug 10.

Confounding by Pre-Morbid Functional Status in Studies of Apparent Sex Differences in Severity and Outcome of Stroke

Christel Renoux  1 , Janie Coulombe  2 , Linxin Li  2 , Aravind Ganesh  2 , Louise Silver  2 , Peter M Rothwell  2 ; Oxford Vascular Study
Affiliations

Confounding by Pre-Morbid Functional Status in Studies of Apparent Sex Differences in Severity and Outcome of Stroke

Christel Renoux et al. Stroke. 2017 Oct.

Abstract

Background and purpose: Several studies have reported unexplained worse outcomes after stroke in women but none included the full spectrum of symptomatic ischemic cerebrovascular events while adjusting for prior handicap.

Methods: Using a prospective population-based incident cohort of all transient ischemic attack/stroke (OXVASC [Oxford Vascular Study]) recruited between April 2002 and March 2014, we compared pre-morbid and post-event modified Rankin Scale score (mRS) in women and men and change in mRS score 1 month, 6 months, 1 year, and 5 years after stroke. Baseline stroke-related neurological impairment was measured with the National Institutes of Health Stroke Scale.

Results: Among 2553 patients (50.6% women) with a first transient ischemic attack/ischemic stroke, women had a worse handicap 1 month after ischemic stroke (age-adjusted odds ratio for mRS score, 1.35; 95% confidence interval, 1.12-1.63). However, women also had a higher pre-morbid mRS score compared with men (age-adjusted odds ratio, 1.58; 95% confidence interval, 1.36-1.84). There was no difference in stroke severity when adjusting for age and pre-morbid mRS (odds ratio, 1.10; 95% confidence interval, 0.90-1.35) and no difference in the pre-/poststroke change in mRS at 1 month (age-adjusted odds ratio, 1.00; 95% confidence interval, 0.82-1.21), 6 months, 1 year, and 5 years. Women had a lower mortality rate, and there was no sex difference in risk of recurrent stroke.

Conclusions: We found no evidence of a worse outcome of stroke in women when adjusting for age and pre-morbid mRS. Failure to account for sex differences in pre-morbid handicap could explain contradictory findings in previous studies. Properties of the mRS may also contribute to these inconsistencies.

Keywords: epidemiology; prognosis; sex; stroke; women.

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Figures

Figure 1.
Figure 1.
Distribution of modified Rankin Scale (mRS) 1 month after stroke among men and women (A) and mRS before stroke (B). CI indicates confidence interval; and OR, odds ratio.
Figure 2.
Figure 2.
Distribution of National Institutes of Health Stroke Scale score among men and women with ischemic stroke only. mRS indicates modified Rankin Scale; OR, odds ratio; TIA, transient ischemic attack; and TOAST, Trial of ORG 10172 in Acute Stroke Treatment.
Figure 3.
Figure 3.
Distribution of the change in modified Rankin Scale score before and 1 month after the ischemic stroke by sex and age category.
Figure 4.
Figure 4.
Mortality rates per 1000 person-years during the first year or during the entire study period.
See this image and copyright information in PMC

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