Intraregional decline in case-fatality and hospital use after occlusive stroke in the Southeastern United States.

OBJECTIVE: To identify changes in mortality and hospital use among patients admitted for ischemic stroke in Alabama. BACKGROUND: The decline in stroke mortality in the Southeast is greater than in other US regions. Whether this decline in a result of decreased incidence or improved case-fatality rates is unknown. METHODS: We examined Medicare hospitalization data from approximately 625,000 beneficiaries and identified patients admitted for ischemic stroke between January 1992 and December 1994. The search was carried out using International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) codes pertinent to all diagnoses related to ischemic stroke. Data relevant to mortality and length of stay (LOS) were collected, and comparisons were made of the average case-fatality rate and LOS in each of the 3 years. RESULTS: No significant difference was found in the incidence of ischemic stroke during the 3 years. The number of admissions was 4438 for 1992, 4124 for 1993, and 4762 for 1994. Conversely, the average LOS showed a significant decline, with values of 10.05, 9,36, and 8.72 days, respectively (P<.0003). A significant decline in mortality, with average case-fatality rates of 11.72%, 11.56%, and 9.71%, respectively (P<.003), was also found. CONCLUSION: These data suggest that the decline in stroke mortality in the Southeast is because of improved patient survival after stroke, rather than decreased incidence. Although several factors may be contributing to the decreased case-fatality rates, improved care of hospitalized stroke patients is likely of primary importance. Additionally, decreased mortality associated with decreased LOS suggests more efficient hospital use.

Persistence and extinction of local populations of the garden snail Helix aspersa in unfavorable environments.

In southern California, previously disturbed but currently uncultivated habitats are unfavorable environments for the introduced snail Helix aspersa. In these habitats, snails were often distributed in small, local populations only a few meters apart. Migration between neighboring populations was minimal because the snails have strong homing tendencies. Local micro-environmental differences produced differences in the demographic properties of 4 adjacent populations during studies spanning 5 years.The major unfavorable feature of these habitats was 6-8 months annual drought which caused slow and intermittent population growth. Snails nested successfully only 3 times in 5 years, but juveniles from only 2 of these cohorts reached sexual maturity. Most growth was restricted to the spring and snails were up to 4 years old when they matured, except for one population where additional water during dry weather enabled snails to mature in 6-8 months.At least 74% of deaths were caused by small mammals, and one population went extinct when adverse physical conditions prevented recruitment during a period of heavy mortality. Adverse physical conditions alone did not lead to population declines or extinctions.