The changing epidemiology of infantile hypertrophic pyloric stenosis in Scotland.

Background: The aetiology of infantile hypertrophic pyloric stenosis (IHPS) has not been fully elucidated. Since the 1990s, a sharp decline in IHPS has been reported in various countries. Recent research from Sweden reported a correlation between falling rates of IHPS and of sudden infant death syndrome (SIDS). This was attributed to a reduction in the number of infants sleeping in the prone position following the "Back to Sleep" campaign.

Objectives: To describe the changing epidemiology of IHPS in Scotland, to examine the relationship between IHPS and SIDS rates and to examine trends in other factors that may explain the observed reduction in IHPS incidence.

Design: Incidence rates of IHPS and SIDS were derived from routine data and their relationship analysed. Trends in mean maternal age, maternal smoking, mean birth weight and breastfeeding rates were also examined.

Setting: The whole of Scotland between 1981 and 2004.

Results: IHPS incidence fell from 4.4 to 1.4 per 1000 live births in Scotland between 1981 and 2004. Rates were consistently higher in males, although the overall incidence patterns in males and females were similar. Rates showed a positive relationship with deprivation. The fall in the incidence of IHPS preceded the fall in SIDS by 2 years and the incidence of SIDS displayed less variability than that of IHPS. Significant temporal trends were also observed in other maternal and infant characteristics.

Conclusion: There has been a marked reduction in Scotland's IHPS incidence, but this is unlikely to be a consequence of a change in infant sleeping position.