Living at high altitude and risk of sudden infant death syndrome

Objective-To investigate the association between altitude of residence and risk of sudden infant death syndrome (SIDS). Methods-A retrospective, case control study in the Tyrol, Austria enrolled 99 infants with SIDS occurring between 1984 and 1994, and 136 randomly sele cted control cases. Data on pregnancy, delivery, child care practice, and s ociodemographic characteristics including altitude of residence were collec ted with a standardised questionnaire. Results-The risk of SIDS increased gradually with increasing altitude of re sidence. This relation remained independently significant when the analysis was adjusted for gestational age, birth weight, prenatal care, mother's ag e at delivery, educational level of parents, and cigarette smoking during p regnancy. The prone sleeping position emerged as an obligatory cofactor in this association. In the whole of Austria, a similar trend of association e merged between the average altitudes in the 99 political counties and the r ates of SIDS. Conclusions-This study identified altitude of residence as a significant ri sk predictor of SIDS, primarily in combination with the prone sleeping posi tion. Respiratory disturbances, reduced oxygen saturation, and lower temper atures at high altitude might explain this association.