The Lehigh Valley Recurrent Stroke Study: Description of Design and Methods

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Abstract
A community-based, prospective study was carried out in the Lehigh Valley to determine how 5 selected risk factors and their control affected the frequency of stroke recurrence and death after an initial stroke. The initial stroke was verified clinically and by computerized tomography. Between 1987 and 1989, 662 patients with an initial stroke were enrolled and followed regularly every 4–6 months for up to 7 visits. The average follow-up period was 2 years. The risk factors selected included hypertension, myocardial infarction, cardiac arrhythmia, diabetes mellitus and transient ischemic attacks. Interim death and its cause were noted. Surviving patients were interviewed and examined to determine whether a second stroke has occurred. At enrollment, 51.4% of the cohort was male. The average age of men was 69.6, while women were older, averaging 74.3 years. Stroke types were thrombosis, 14%; embolus, 23%; lacune, 9%; nonspecific infarct, 48%, and intracerebral hemorrhage, 6%. There were 138 deaths (21 %) and 81 second strokes (12%) during follow-up. The frequency of risk factors at enrollment was as follows; hypertension, 59%; myocardial infarction, 25%, cardiac arrhythmia, 47% (of which 16% had atrial fibrillation); diabetes mellitus, 29%, and transient ischemic attack, 18%. Of course many patients had multiple risk factors. We analyzed whether the presence of a risk factor at enrollment and its quality of control during follow-up affected stroke recurrence frequency and the mortality rates. These results will be reported in future papers. In this paper, we describe study design details and define the methods used to classify stroke type, risk factor status at enrollment and quality of control of each of the risk factors during follow-up. These details will be referred to in subsequent reports and will permit comparisons of the Lehigh Valley Stroke Cohort with other stroke cohorts.

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