Objectives: To determine whether the prevalence of known risk factors and the magnitude of their association with sudden infant death syndrome (SIDS) differed between weekends and weekdays.
Method: A large nationwide case-control study, comparing interview data for 393 cases with 1591 controls.
Results: Sudden infant death syndrome occurred more often at weekends, more deaths occurring on Sunday than on any other day of the week. Significant interaction effects were found between weekends and sharing a room with an adult and the parents going to a party. After adjustment for confounders, room sharing was less protective at the weekends (odds ratio (OR) = 0.66, 95% confidence interval (CI) 0.43 to 1.03) than it was on weekdays (OR = 0.41, 95% CI 0.30 to 0.57) using not room sharing and weekdays as the reference group. Although the likelihood of SIDS after a party was higher at weekends (OR = 2.47, 95% CI 1.11 to 5.47) than on weekdays (OR = 0.55, 95% CI 0.21 to 1.37), few cases were reported. Being Maori (OR = 3.35, 95% CI 1.75 to 6.43) or the child of an unmarried mother (OR = 3.91, 95% CI 2.20 to 6.92) were risk factors for SIDS occurring on Sundays.
Conclusions: The increase in SIDS at weekends may be explained in part by the lesser protective effect of sharing a bedroom with an adult at that time. It may also be related to social activities that occur at weekends.