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 m atched by winter excess morbidity. The aim of the study was to test the pre diction that winter excess morbidity would be observable and would show a s ocial 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 fr equently to outdoor cold exposure. Methods The study was set in the Metropolitan Borough of Stockport and docu mented, from routine health services hospital admissions data, winter and s ummer differences in ACORN-specific, age- and sex-standardized hospital adm ission rates and ratios, for ischaemic heart disease, directly and indirect ly standardized using the Stockport population as the standard. Results The expected social class gradient in ischaemic heart disease admis sions was more clearly observable in the summer than in the winter. Affluen t groups showed winter excess morbidity, less affluent groups showed summer excess morbidity. Conclusion The data serendipitously indicate an alternative hypothesis - th at winter excess morbidity is a feature of health benefits derived in the s ummer and differentially available to the more affluent, such as opportunit ies for outdoor leisure. This hypothesis deserves testing in a study design ed for that purpose, although it is not entirely satisfactory as an explana tion of existing data.