Winter excess morbidity: is it a summer phenomenon?

BACKGROUND: It was hypothesized that winter excess mortality is a feature of ill health produced by exposure to ambient low temperatures, and will be matched by winter excess morbidity. The aim of the study was to test the prediction that winter excess morbidity would be observable and would show a social class gradient with greater excesses in less affluent groups, who are less able to heat their houses or whose lack of a car exposes them more frequently to outdoor cold exposure. METHODS: The study was set in the Metropolitan Borough of Stockport and documented, from routine health services hospital admissions data, winter and summer differences in ACORN-specific, age- and sex-standardized hospital admission rates and ratios, for ischaemic heart disease, directly and indirectly standardized using the Stockport population as the standard. RESULTS: The expected social class gradient in ischaemic heart disease admissions was more clearly observable in the summer than in the winter. Affluent groups showed winter excess morbidity, less affluent groups showed summer excess morbidity. CONCLUSION: The data serendipitously indicate an alternative hypothesis - that winter excess morbidity is a feature of health benefits derived in the summer and differentially available to the more affluent, such as opportunities for outdoor leisure. This hypothesis deserves testing in a study designed for that purpose, although it is not entirely satisfactory as an explanation of existing data.