Impact of functional status at six months on long term survival in patients with ischaemic stroke: prospective cohort studies

Objective To estimate the impact on long term survival of functional status at six months after ischaemic stroke.Design Prospective cohort study.Settings Three cohorts: Oxfordshire community stroke project, Lothian stroke register, and the first international stroke trial (in the United Kingdom).Participants 7710 patients with ischaemic stroke registered between 1981 and 2000 and followed up for a maximum of 19 years.Main outcome measures Functional status at six months after stroke assessed with modified Rankin scale or “two simple questions.” Mortality during follow-up. Survival analysis with Kaplan-Meier curves, log rank test, and Cox’s regression model.Results In a combined analysis of all three cohorts, among patients who survived to assessment six months after the index stroke, the subsequent median length of survival among those independent in daily living and those dependent was 9.7 years (95% confidence interval 8.9 to 10.6) and 6.0 years (5.7 to 6.4), respectively. In a combined analysis of the Oxfordshire and Lothian cohorts, subsequent median survival fell progressively from 12.9 years (10.0 to 15.9) for patients with a Rankin score of 0-1 at six months after the stroke to 2.5 years (1.4 to 3.5) for patients with a Rankin score of 5. All previously stated differences in median survival were significant (log rank test P<0.001). The influence of functional outcome on survival remained significant (P<0.05) in each cohort after adjustment for relevant covariates (such as age, presence of atrial fibrillation, visible infarct on computed tomography, subtype of stroke) in a Cox’s regression model.Conclusion Functional status six months after an ischaemic stroke is associated with long term survival. Early interventions that reduce dependency at six months might have positive effects on long term survival.