Physique and serum lipids of young London busmen in relation to ischaemic heart disease.

Earlier studies of white London busmen revealed that the ischaemic heart disease experience of conductors is better than that of drivers. Various factors which might be related to this difference have been considered, and earlier investigations have established that the physique and serum lipid concentrations of men in these two occupations are different. Since men in the younger occupational groups (25 to 29 years) showed some of these differences the suggestion has been made that conductors may be constitutionally different from drivers. The purpose of this paper is to report a study of the physique and serum lipid concentrations of young recruits for bus driving and conducting at an earlier age than in previous studies and before any occupational factors could have exerted an effect. Physical differences between the two groups of recruits were shown to exist. British bus driver recruits in the age group 21 to 24 years were on average 2·6 cm. taller than British conductor recruits. This is probably because selection favours the recruitment of taller men for driving. New entrant drivers were on average 7·3 lb. (3·3 kg.) heavier, approximately 1 cm. broader across the shoulders, and between 2 and 3 cm. bigger round the chests and waists than conductors. It is shown that these differences are mainly secondary to differences in height. Drivers recruited from the ranks of existing conductors resembled new entrant drivers in everything but height. British driver trainees carried more skin fat and had a tendency to higher serum lipid concentrations than conductors. This is shown to be neither secondary to differences in height nor occupationally acquired. The importance of these findings in relation to the differing ischaemic heart disease experience of bus drivers and conductors is discussed. It is suggested that the underlying factor responsible for the known later physical differences and different ischaemic heart disease experience of London bus drivers and conductors might be a common genetic one.