Follow up study of children born to mothers resident in Seascale, West Cumbria (birth cohort).

Records on 1068 children who were born to mothers resident in Seascale Civil Parish during 1950-83 were studied. There was a large degree of mobility among the families, and nearly half of the children did not subsequently attend the main local school. Use of the National Health Service Central Register, however, enabled us to follow up the children's records regardless of place of residence. The excess of leukaemia among Seascale children first supported from the analysis of geographical areas is confirmed. There were five deaths from leukaemia identified to 30 June 1986 compared with 0.53 expected at national rates--a ratio of 9.36 (95% confidence interval 3.04 to 21.84). One of these deaths occurred after the child had left Seascale. There were four deaths from other cancers compared with 1.06 expected--a ratio of 3.76 (95% CI 1.02 to 9.63). In addition, three further cases of cancer, apart from the deaths, were reported compared with 1.19 expected since 1971--a ratio of 2.53 (95% CI 0.52 to 7.40). For other causes of death, including stillbirths and infant mortality, there was a reported deficit compared with national rates, some of which at least was to be expected on the basis of the social class composition of the population of Seascale. In view of the importance of this cohort of births continued follow up is planned, with the possibility of extending it to include births since 1983, and the methods available for this type of study will be examined further.