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Lancet. 1991 Jun 8;337(8754):1393-7.

Seasonality of disease in Kuwait.

Author information

1
Department of Medicine and Therapeutics, University of Aberdeen, UK.

Abstract

To compare the seasonal variation in total mortality and deaths from cardiovascular, respiratory, and malignant disease, data were collected from North-East Scotland (Grampian region) and Kuwait. Seasonal differences were similar, in both timing and degree, for total mortality and deaths from circulatory disease, but were greater in Kuwait for respiratory disease. Peak mortality was during winter in both areas: in Grampian, when the climate is most uncomfortable, and in Kuwait, when the climate is at its most comfortable. Socioeconomic changes in Kuwait have been accompanied by a rapid fall in the degree of seasonality (deseasonality) for both total and infant mortality. These findings suggest that mortality peaks in winter, not because of a seasonally low temperature, but because of a seasonal fall in mean temperature irrespective of the annual mean temperature.

PIP:

Seasonality of total mortality in Kuwait and causes of death from cardiovascular, respiratory, malignancy, injuries and poisoning, and all other diseases was analyzed by the cosinor method, and compared to data from Grampian, East Scotland as an example of an industrialized area. Data for Kuwait were taken from Ministries of Public Health and of Planning. For cosinor analysis, the mean mortality from each cause was computed, and the percent change for each month is called amplitude. For Kuwait the total mortality peaks in winter, with a declining amplitude, from 20% in the mid-1970s, to about 10% in the mid 1980s. Improved public health typically causes this reduction in seasonal amplitude, called deseasonality. Kuwait's seasonal deaths are largely due to 40% seasonality in cardiovascular deaths. Deaths due to malignancy, injuries and poisonings, and all other deaths are not seasonal. In comparison, in Grampian, 60% of total mortality is cardiovascular and is seasonal, and injuries and all other diseases are also seasonal, while malignancies are not seasonal. The phasing of seasonal cardiovascular deaths is similar in both locations, with similar peaks of about 20% in January. For both areas the timing of respiratory deaths peaks in February, but the amplitude is 46% for Kuwait compared to 33% for Grampian. Kuwait also had significant winter peaks for infectious and parasitic diseases, congenital anomalies and perinatal deaths, accounting for 27% of all deaths, while these causes made up only 2% of deaths in Scotland. Kuwait has a relatively higher proportion of infant deaths, 24.7%, with seasonality, while Grampian has more deaths of elderly 75, 48%, also seasonal. Both locations are in the northern hemisphere, with lowest temperatures in the winter. Grampian's July mean temperatures, however are similar to Kuwait's January mean. Grampian also differs from Kuwait in a much wider variation in photoperiodicity, or day length. The reasons why mortality peaks in warm climates in pleasant winter conditions is not known.

PMID:
1674772
DOI:
10.1016/0140-6736(91)93069-l
[Indexed for MEDLINE]

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