Inequalities in death--specific explanations of a general pattern?

In the Whitehall study, 17 530 civil servants were classified according to employment grade, and their mortality was recorded over 10 years. There was a steep inverse relation between grade and mortality. Compared with the highest grade (administrators), men in the lowest grade had 3 times the mortality rate from coronary heart disease, from a range of other causes, and from all causes combined. This is larger than the mortality differences, nationally, between classes I and V. Smoking and other coronary risk factors are more common in the lowest grades, but these differences account for only part of the mortality difference. The similarity of the risk gradient from a range of specific diseases could indicate the operation of factors affecting general susceptibility. The inverse relation between height and mortality suggests that factors operating from early life may influence adult death rates.