Functional status three months after the first ischemic stroke is associated with long-term outcome: data from a community-based cohort

Abstract

Background: The impact of public health interventions to reduce disability after stroke may be underestimated if only the modest effects on short-term disability are measured. We estimated the impact of differences in short-term functional outcome on long-term functional outcome.

Methods: In a prospective community-based study from October 1998 to September 2000, the first-ever ischemic strokes were registered in a population of 95,816 in Northern Portugal. Patients were examined at baseline and followed-up at three months, one and seven years. The Oxfordshire classification and the Unified Neurological Stroke Scale were used to define the stroke type and the severity of neurological impairments. The functional status was assessed with the modified Rankin Scale (mRS). Ridit analysis was used to estimate the odds of a more serious 7-year outcome based on the adjacent values of the 3-month mRS. Cox proportional hazards models were used for estimating the effect of 3-month mRS on survival, adjusting for patients' characteristics, stroke type and severity.

Results: The odds of a more serious 7-year outcome was different among patients with mRS = 1 and 2 and also with mRS = 3 and 4, defining the no significant (mRS = 0-1), moderate (mRS = 2-3) and severe disability (mRS = 4-5). Of the 380 first-ever strokes, at 3 months, 126 (33.2%) had mRS <2, 114 (30.0%) mRS = 2-3, 73 (19.2%) mRS = 4-5, and 67 (17.6%) had died. We found linear relations between the 3-month mRS and the patient's baseline profile, stroke type and severity. The Kaplan-Meier 7-year survival estimates for 3-month survivors with mRS 0-1, 2-3 and 4-5 were 67, 50 and 23%, respectively. For mRS at 3 months of 2-3 versus 0-1 the hazard ratio (HR) for death was 1.61, (95% CI: 1.10-2.38) and for mRS = 4-5 versus 2-3 the HR was 2.20 (95% CI: 1.52-3.20); after adjustment the HRs were 1.19 (95% CI: 0.77-1.84) and HR = 1.87 (95% CI: 1.18-2.95), respectively. A change in the 3-month mRS from 4-5 to 2-3 would have a 'number needed to change' of 9 (95% CI: 6-18) patients to avoid one death in the long run; identical outcome is obtained by shifting the mRS from 2-3 to 0-1 in 27 (95% CI: 15-141) patients.

Conclusions: In patients with ischemic stroke who survive to 3 months, a three grade simplified mRS summarizes the patient risk profile and stroke characteristics. These data confirm that modest differences in the functional status at 3 months are associated with significant differences in survival and functional status over 7 years follow-up and have implications for health care planning and the health economic assessment of treatments for acute stroke.