Cot deaths in Birmingham.

The spatial and temporal distributions of cot deaths and of infant respiratory deaths in Birmingham between 1964 and 1984 were examined. Respiratory deaths declined and cot deaths increased, and the combined rate showed a downward trend. Seasonal variations were identical in the two groups and in each case were more powerfully related to date of death than to date of birth. Cumulative mortalities were parallel by age, depended crucially upon the quarter of the year in which the child was born, and were identical for the two classes of death. The separation of the temporal trends probably owed more to changes in diagnostic practice than to biological or epidemiological processes. Powerful space-time interactions were detected for both groups and for cross-pairs belonging to different groups. There was a four-yearly oscillation in the combined death rate, of doubtful statistical significance, but synchronous with a similar oscillation reported by other investigators using national data. The four-yearly oscillation was also synchronous with the four-yearly pattern for national isolations of Mycoplasma pneumoniae.