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Seasonality and the sudden infant death syndrome during 1987-9 and 1991-3 in Australia and Britain
A S Douglas1, T M Allan, P J Helms
1Department of Medicine and Therapeutics, University of Aberdeen Medical School, Foresterhill.
Objective:
To determine whether seasonality of the sudden infant death syndrome persists now that rates have fallen, mostly after widespread adoption of the "face upwards" sleeping position.
Design:
Monthly data on the sudden infant death syndrome during 1987-9 were compared for seasonality with those of 1991-3; rates were studied as deaths per 1000 live births.
Setting:
Australia and Britain (England, Wales, and Scotland).
Subjects:
Infants under 1 year dying of the syndrome (2401 for Australia and 6630 for Britain).
Main Outcome Measure:
Extent of seasonal variation (amplitude) was established by cosinor analysis; amplitudes for the earlier and later years were compared.
Results:
The rate fell in every month, and, though it did so relatively more in winter than summer, seasonality remained a distinctive feature. In the comparison of amplitudes the ratio between the earlier and later years was 1.4 in both Australia and Britain. Some differences between the hemispheres were noted.
Conclusions:
Seasonality of the sudden infant death syndrome remains to be explained and continues to be an important aetiological lead. Studies from other countries are needed.