Differences between long-term participants and non-responders in a study of coalminers’ respiratory health and exposure to dust

We examined data from a sample of 7624 coalminers who attended medical surveys held in the 1960s at 24 collieries in Britain in order to investigate differences between long-term participants and non-responders in a long-term study. About 11 years later, 1305 men had died and of the survivors 4833 attended, with 1486 failing to respond.

The representativeness of those who where re-examined was studied by comparing the characteristics of these three groups at the time of the earlier surveys. Lung function, measured by FEV1 and by FVC, was found after adjustment for other variables to be lower in those who subsequently died. There were also differences in adjusted lung function values between men who died from different causes; lower lung function was associated particularly with deaths ascribed to non-malignant respiratory disease. However, there was no evidence that the slope of the inverse relationship between lung function and exposure to respirable dust differed between the groups. There was no evidence, therefore, of increased susceptibility to the effects of dust in those who did not attend. It is concluded that cross-sectional estimates of the effect of coalmine dust on lung function from later surveys are unlikely to have been seriously biased by non-response among those surveyed initially.