Secular trends of sudden infant death syndrome and other causes of post perinatal mortality in Norwegian birth cohorts 1967-1984.

Lack of positive diagnostic criteria and increasing professional concern, probably causing increasing ascertainment, have rendered reported increases in SIDS-rates controversial. However, these problems related to cause specific mortality do not apply to the total mortality. Due to the exceptional age-at-death distribution of SIDS cases, the SIDS fraction of all deaths increases during the first year of life to reach a maximum, in the present study of 56%, from the 105th through the 125th day of life. During these days, the total mortality rate in Norway increased from 0.24 per 1,000 in 1971-72 to 0.46 in 1983-84. Thus, the observed trend, with an increase in the SIDS rate from 1.02 per 1,000 in 1971-72 to 2.34 in 1983-84, is considered true. Observed in a country where perinatal and neonatal mortality have decreased for a long period of time and still remain very low in a global perspective, the increasing SIDS rate is a matter of great concern.