Re Wigfield

Can the fall in Avon's sudden infant death rate be explained by changes in sleeping position?

OBJECTIVE--To examine the impact of changing practice with regard to infant sleeping position on mortality from the sudden infant death syndrome. DESIGN--A population based study of all infants dying suddenly and unexpectedly during February 1990 to July 1991, and two groups of controls; one comprising every 125th baby born to Avon residents and the other comprising pairs of infants matched to each index case for age, neighbourhood, and date of study. Information about sleeping position was collected at home visits soon after the index babys death or, for the population based controls, on several occasions in the first six months of life. The design was comparable to that of an earlier study of the same population. SETTING--County of Avon. SUBJECTS--35 infants who died suddenly and unexpectedly (32 of the sudden infant death syndrome), 70 matched controls, and 152 population based controls. RESULTS--The prevalence of prone sleeping in the matched controls was much lower than that found in an earlier study in Avon (28% (18/64) 1990-1 v 58% (76/131) 1987-9; p less than 0.001) and was comparable with the prevalence in population based controls (29%). This would be expected to lead to a reduction in the incidence of the sudden infant death syndrome to 2.0/1000 live births (95% confidence interval 1.8/1000 to 2.5/1000). The actual mortality fell from 3.5/1000 in 1987-9 to 1.7/1000. CONCLUSION--The fall in mortality can be almost entirely accounted for by the reduction in prone sleeping, suggesting a causal relation exists between them. Side and supine positions confer protection but the side position is unstable and the infant may roll prone. We therefore recommend supine as the safest sleeping position for babies.

SIDS: risk reduction measures

Increasing public awareness of the prone sleeping position, maternal smoking and overheating as potentially avoidable risk factors for the sudden infant death syndrome (SIDS) has been accompanied by a dramatic reduction in mortality. The results of two population based studies of SIDS in Avon are compared; the first one occurred before these risk factors were widely known and during the second study there was a gradual increase in publicity. Between the studies the prevalence of prone sleeping in the control populations fell significantly from 60% to 28% and almost all of the reduction in SIDS mortality (3.5 to 1.7 per thousand live births) could be attributed to this change. Other changes were also found: the seasonal pattern of incidence was lost, the proportion of expreterm babies increased and the male predominance was accentuated. The relative importance of smoking and bottle feeding appeared to increase whereas the odds ratios for heavy wrapping and overnight heating were no longer significantly elevated. Small numbers limit the significance of these individual variations but demonstrate that changes are occurring. Local and national public health campaigns have been launched in the UK and abroad to encourage infant care practices that reduce the risk of SIDS. Monitoring the effectiveness of these campaigns is important and may allow new risk factors to be identified which could in turn be targeted in future preventative campaigns. Significant reductions in mortality have followed these initial campaigns but in order to maintain them the message must be regularly renewed using an appropriate approach and effective channels of communication to target high risk families within the community.

Electric and magnetic fields of 50 Hz are not associated with sudden infant death syndrome

Sudden infant death syndrome (SIDS) is a multifactorial condition. Power frequency magnetic fields have been implicated in SIDS. Through the use of a case-control study measuring 50 Hz electric and magnetic fields at the SIDS babys last head position, no association could be found between SIDS and either electric (p = 0.327) or magnetic (p = 0.827) 50 Hz fields.