We investigated the seasonal pattern of stroke using the Lehigh Valley Stroke Register. This register includes all patients hospitalized with stroke or transient ischemk attack (TIA) from among the 600,000 Lehigh Valley residents. Meterological data were obtained from the National Oceanic and Atmospheric Administration. The study, which uses 18 months of data, included 1,944 cases. Using single harmonic regression analysis, the seasonal pattern of TIA and infarction, but not hemorrhage, fit a sine-cosine wavefunction with a 12-month period (R 2 = 41% and 36%, respectively). For infarction, the strongest seasonal pattern was exhibited for women of all ages and for both sexes in the age groups 65-74 and 75-84, but only the sine component was significant. The peak months for TIA were June-August, while the peak months for infarcts were February-April. Correlations between ambient temperature and each type of stroke were computed. A significant positive correlation for TIA was found (r = 0.57, p = 0.01). After adjusting for a 2-month lag between the low for infarction and the peak for temperature, a significant negative correlation was found (r = -0.64, p = 0.01). No significant correlation was found for hemorrhage. Possible reasons for the opposite relations of TLA and infarct are discussed. (Stroke 1987; 18:38-42)

We investigated black/white differences in stroke rate (standardized morbidity), severity, and subtype, and the relative frequencies of 5 primary risk factors (hypertension, diabetes, myocardial infarction, other heart diseases, and transient ischemic attack [TIA]) using the Lehigh Valley Stroke Register. Blacks had a statistically significant higher, age-adjusted rate of stroke than whites. We found no differences in stroke severity using our measures but blacks had a statistically higher proportion of lacunar stroke, while whites had a higher proportion of embolic stroke. There were no differences in proportions of thrombotic stroke or intracerebral hemorrhage. The relative frequencies of hypertension, myocardial infarction, other heart diseases, and diabetes were higher for blacks, while the relative frequency of TIA was higher for whites. These observations are consistent with other reports that blacks have a higher frequency of stroke and tend to have more small-vessel cerebrovascular pathology than whites.

Age-specific risk of recurrent stroke for various risk factors, calculated independently, was estimated using the first year of data from the Lehigh Valley Stroke Register. The register is based on a population of more than one-half million. Among the risk factors examined, the highest overall risk of recurrent stroke, 41.4, occurred with a history of at least one transient ischemic attack (TIA). After myocardial infarction (MI), the relative risk of a recurrent stroke was 8.0, while with all other heart diseases combined it was 8.4. With diabetes, the relative risk of a recurrent stroke was 5.6; with hypertension, it was 4.5. The relative risk increased with age after TIA and MI, but not for other heart disease, diabetes, and hypertension, except in the 85+-year-old age group.

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