Absence of detrimental effect of the carrier state for the cystic fibrosis gene.

The most frequent, lethal, hereditary disease among white children in the United States is the recessively inherited cystic fibrosis of the pancreas, the birth incidence rate being approximately 4 per 10,000, as judged from a comprehensive survey in New England (1). This high frequency would be associated with a high frequency of heterozygous carriers, approximately 4 per cent among white persons. If, as has been suggested (2-10), carriers of the cystic fibrosis · gene have an increased susceptibility to, or incidence of, respiratory disease, they could comprise an important segment of the population so afflicted. The present study was undertaken in an effort to determine whether cystic fibrosis heterozygotes are, in fact, more susceptible to respiratory disease, or, for that matter, to any disease.