Cystic fibrosis in Ontario.

The incidence of cystic fibrosis in Ontario, Canada has been determined from clinical data, from the cystic fibrosis database of the Hospital for Sick Children, Toronto, and from population statistics in the Province of Ontario. The survey included 420 confirmed cases of cystic fibrosis born during the period 1966-1980. The mean incidence during this period was one in 2,927. In the last 5-year period, a decline was noted in incidence that may have reflected in part the effectiveness of early diagnosis and genetic counseling in affected families. During the period of the survey, over 60% of cases were diagnosed within the first year of life, 74% by age 2 years, and 90% by age 5 years. Clinical diagnosis in the first year of life was more common in males (65%) than in females (54%), a consistent finding during the period of the survey. The incidence of meconium ileus was 15.7% of ascertained cases of cystic fibrosis, with similar incidences in males (16.4%) and females (14.4%). Although survival has not been the subject of this survey, mortality in the neonatal period was significantly higher in males than in females with cystic fibrosis.