Shift work, occupation and coronary heart disease over

Abstract

ObjectivesThe risk of coronary heart disease (CHD) in shift work and the possible pathways for CHD in industrial workers were studied along with the importance of shift work as an occupational class gradient of CHI) risk. Methods Data from a psychosocial questionnaire and on life-style factors, blood pressure, and serum lipid levels were used for a follow-up study of a cohort of 1806 workers. CHD was determined from official Fi~~nish registers. Cox's proportional hazards models were used with different covariates to evaluate the relative rislcs associated with shift work. Results All the blue-collar workers smoked more and a had higher systolic blood pressure than the whitecollar workers. Three-shift workers scored low for job-decision latitude on the Karasek job stress scales. There were no differences in the total cholesterol or high-density lipoprotein cholesterol levels. When all the shift workers were compared with all the day workers, the relative risk of CHD was 1.5 [95% confidence interval (95% CI) 1.1-2.11 when only age was adjusted for and 1.4 (95% CI 1.0-1.9) when life-style factors, blood pressure, and serum lipids were also adjusted for. The blue-collar day workers and 2-shift and 3-shift workers had relative risks of 1.3 (95% CI 0.8-2.0), 1.9 (95% CI 1.1-3.4), and 1.7 (95% CI 1.1-2.7), respectively, when compared with the white-collar day workers. C O~C~U S~O~S Shift work is an important part of the occupational gradient in CHD risk among industrial workers; some evidence was found for the hypothesis that a direct stress-related mechanism explains part of the increased CHD risk.Key terms blood pressure, coronary heart disease, job stress, life-style, occupation, shift work.While most occupational health hazards have been strongly curtailed in Western industrialized countries, shift work remains common. In fact, the number of shift workers has even increased in some branches of industry, for example, in manufacturing (1). The total number of night and shift workers seems to be between some 15% and 20% of the total working population in most European Community countries (1). Approximately 20% of shift workers are forced to move to day work during their first year of employment due to disturbances in their circadian rhythm, with accompanying sleep disturbances, difficulties in social life, and various stress reactions (2). Even those who accommodate may nevertheless be at increased risk of long-term health hazards. Whether or not shift workers are at increased risk of coronary heart disease (CHD) has been studied since the middle of the century with contrasting findings. In 1978 Harrington (3) concluded in his review that there was no conclusive evidence for an increased incidence of cardiovascular disorders for shift workers. After the followup study of Knutsson et a1 (4) and the massive aggregated data study by Alfredsson et a1 (3, Waterhouse and his colleagues (6) found, in their review from 1992, that the evidence in favor of an increased risk of CHD in association with shift work is becoming more...

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