SEASONALITY OF SUDDEN-INFANT-DEATH-SYNDROME (SIDS) BY AGE AT DEATH

Seasonality of sudden infant death syndrome (SIDS) is a well-establish ed epidemiological finding, The purpose of the study was to determine whether this feature varied significantly with age at death. In total, 13 990 cases of SIDS in Scotland, England and Wales during 1982-1992 were studied by age group at death. Seasonality was established by fit ting a sinusoidal curve and for each set of monthly data the peak posi tion in the year and its magnitude were determined. Weighted regressio n revealed significant differences in peak position and amplitude of s easonal variation between those dying at less than or equal to 4 month s and those aged greater than or equal to 5 months at death. Those inf ants in the younger age group were more likely to die earlier in the w inter months and had a smaller variation in seasonality. The peak (acr ophase) months were January for less than or equal to 4 months and Feb ruary for greater than or equal to 5 months at death. Weighted regress ions of peak position and amplitude on ase at death had p-values of <0 .001 and <0.01, respectively. A log linear model relating SIDS inciden ce to month of birth, month of death and age was able to explain some of these findings. The findings support the hypothesis that in SIDS th ere may be more than one infant cohort, each of which passes through a vulnerable developmental window at different ages.