Geographical variations in the incidence of sarcoidosis in Great Britain: A comparative study of four areas: A report to the Research Committee of the British Thoracic and Tuberculosis Association

Abstract

The incidence of sarcoidosis in four areas of Great Britain (Cornwall and Plymouth; East Anglia; Sheffield and neighbouring towns; and North-east and East Scotland) was estimated in a survey during the five-year period 1961–1966. The areas were selected because they have contrasting geographical features and degrees of industrialisation and definable administrative boundaries. Physicians, dermatologists and ophthalmologists in these areas were asked to submit reports of all cases in which sarcoidosis was diagnosed or suspected to a central panel whose opinion on the diagnosis, decided in some instances only after additional investigations or a further review after a period of observation, was accepted for the purpose of the survey. Exceptional efforts were made to ensure reporting of every case, so that for the first time reliable information might be obtained about the annual incidence of sarcoidosis in all its forms in a civil population.The incidence was found to increase from north to south in both sexes, but the range of variation between the areas was much smaller in women than in men. Among women, the highest incidence was 0·45/10,000/year in Cornwall and Plymouth, and the lowest 0·35 in Sheffield. Among men, the highest was 0·41 in Cornwall and Plymouth and the lowest 0·21 in N.E. and E. Scotland. The female/male ratio of annual incidence varied correspondingly from 1·10 in Cornwall and Plymouth, through intermediate figures for East Anglia and Sheffield, to 1·72 in N.E. and E. Scotland.In all four areas, the peak incidence in both sexes was in the age group 25–34 years. In all areas except Sheffield, there was a smaller and less well-defined rise in women over the age of 45 years, accounting for most of the excess of female over male incidence. Sheffield, the one highly industrialised area, showed two differences from the other areas; a very low incidence in both men and women over the age of 45, and an exceptionally high incidence among younger women in the 15–24 year age group.All the cases in all areas occurred in persons of Caucasian stock, 97% of whom had been born in Great Britain. The ABO blood-group distributions of the sarcoidosis patients did not differ from that of the general populations in the four areas. Variations in incidence could not be related to occupational factors, to differences in afforestation, or to tuberculosis rates. The rising incidence from north to south, especially among men, and the peculiar age-distribution in the one heavily industrialised area, especially among women, remain unexplained.