A malfunctioning biological clock (circadian rhythms which recur on a roughly 24-hour basis) may be a factor in SIDS, because of the clock's key role in regulating sleep, temperature and hormonal rhythms. The development of mature stable sleep rhythms is an important part of infant development. The neurological processes involved in the control of the sleep-wake cycle develop and mature between 2 and 6 months of age. The [Adelaide Baby Study] seeks to generate baseline data about the normal development of infants' sleep-wake cycle within the home environment and under contemporary child-caring circumstances. The study is unique in that it looks at normal sleep development in the home rather than in a laboratory environment. Australian research (Adelaide University) also suggests that fluctuating body temperature may be important in SIDS. Young infants have greater difficulty controlling their body temperature than older babies and children. With varying internal temperatures, the fluidity and function of the surfactant lining the lungs may be altered in a way that causes respiratory distress.
However, all kinds of rhythms are important for the well-being of the baby. There is a possibility that the rhythms in children who are at risk of SIDS develop out of synchrony with each other. Drugs taken by the mother during pregnancy may contribute to the lack of synchrony. Three drugs are being studied by scientists in Adelaide: nicotine and caffeine because they are used by many pregnant and breast-feeding women and both have been implicated in adverse changes in the developing foetus; and cocaine because it is a major problem in pregnancy in the USA.