Incidence of ischaemic heart disease and prognostic importance of risk factors in agricultural and industrial populations.

A longitudinal epidemiological study of ischaemic heart disease (IHD) in men aged 40-59 years showed that the five-year incidence of the manifest form was 7.8% in agricultural workers and 9.7% in industrial employees. The corresponding incidence of the latent form was 9.0% and 12.2%, respectively. The differences in the incidence of both forms between the population samples studied was at the border of statistical significance. The importance of risk factors was evaluated on the basis of the score represented by the difference between the respective five-year incidence of IHD in subjects with and without the risk factors concerned. The highest relative scores were found with systolic and diastolic hypertension, positive family history and obesity. For prognostic purposes, the total relative risk, represented by the sum of the scores of the risk factors proved to be useful. Autopsies confirmed that a total relative risk exceeding 40% was a sensitive indicator of morphological substrate of coronary heart disease.