Increasing incidence of club foot with higher population density: incidence and geographical variation in Denmark over a 16-year period--an epidemiological study of 936,525 births.

BACKGROUND

The occurrence of club foot (CF) varies between countries and populations, and may be related to endogenous and exogenous factors. We analyzed the occurrence of CF in a whole country over a long period of time (16 years).

METHODS

Patients born in Denmark with a foot deformity 1978-93 were identified from the National Patient Register and the Register of Inborn Malformations. The records for each patient were studied in the hospital departments to establish the diagnoses and to obtain additional information. Demographic data were obtained from the Danish National Demographical Institute and from the Danish Population Register.

RESULTS

The incidence of isolated CF was 1.2/1,000 live births. It increased significantly during the study period, and the incidence of CF and the standardized morbidity ratio for CF were significantly positively correlated to population densities in the counties and the districts. There was no significant increase in the relative proportion of children with CF born to non-Scandinavian parents during the period.

INTERPRETATION

The increasing incidence of isolated CF with higher population density indicates that there may be exogenous factors that are pathogenic.