Epidemiology of sarcoidosis in the Isle of Man--1: A case controlled study.

A case controlled study of 96 cases of sarcoidosis has been carried out in the Isle of Man. Age and sex matched controls were selected at random from the pathology and radiology records, which cover 85% of the resident population, and a second control group was drawn from a tuberculosis register. Special efforts were made to achieve a high level of ascertainment. In this study most cases occurred in young adults. It affected the sexes equally and occurred more frequently in the indigenous Manx population. Thirty eight cases (39.6%) had been in contact with the disease before diagnosis, compared with two (1.2%) of the combined controls. These contacts included members of the same household, colleagues at work, and close friends. A bias may have been introduced as patients would inevitably be more aware of the disease and be more likely to mention previous contact than the controls. Nevertheless, the evidence is considered to support the view that sarcoidosis is a communicable disease.

Epidemiology of sarcoidosis in the Isle of Man--2: Evidence for space-time clustering.

The case-control test for space-time clustering developed by Pike and Smith was applied to 96 cases of sarcoidosis diagnosed in the Isle of Man from 1962 to 1983. There were significantly more links between cases separated by time intervals of less than 10 years and distances of less than 100 metres than between the others. Analysis of the type of links indicated that clusters consisted of pairs whose contact was by place of residence or work. More linked cases were diagnosed less than three years apart than would be expected by chance. These findings lend support to the idea that sarcoidosis is a communicable disease.

Incidence of sarcoidosis in the Isle of Man.

The incidence of sarcoidosis in a clearly defined island community has been determined in a seven year study. Special efforts were made to identify all cases, including those presenting to their general practitioners with only minor symptoms. A mean incidence of 14.7 per 100 000 per annum has been found in the years 1977-83 compared with an annual incidence of 3.5 per 100 000 in the preceding 15 years, when no specific attempts were made to identify sufferers from sarcoidosis. The lower figure is similar to the reported incidence in the United Kingdom and the difference is considered to be due to increased detection of cases during the study period. These findings suggest that a large proportion of cases of sarcoidosis in a general population may not be recorded in a registration system.