Hanna Virkkunen

Objectives The change in systolic blood pressure (SBP) over an 8-year period was explored in groups defined according to exposure to shift work, occupational noise, and physical workload. The impact of baseline SBP and its increase in relation to coronary heart disease (CHD) risk due to these exposures was also studied. Methods The study cohorts (N=1288 for CHD follow-up, N=884 for SBP follow-up) consisted of industrially employed middle-aged men from the Helsinki Heart Study. Shiftwork status was obtained from a questionnaire, and other exposures were determined with the Finnish job-exposure matrix. SBP was measured in the Helsinki Heart Study, and CHD end points were obtained from official Finnish registers. The joint effects of baseline SBP, its change, and the exposure in question were estimated via Cox´s regression models. Results During the SBP follow-up, the steepest SBP gradient was found for physical workload only and physical workload combined with noise; shift work alone or combined with noise primarily entailed a lower mean SBP level than no such exposure. However, the shift workers had a relative risk of 1.71 [95% confidence interval (95% CI) 1.01–2.87] even without an increase in SBP, but, with a baseline SBP of ≥140 mmHg and an additional increase, their relative risk rose to 4.62 (95% CI 2.31–9.24) when they were compared with day workers with an SBP of <140 mmHg and no increase. Conclusions In general, shift workers do not develop higher SBP levels than day workers, but, if they do, it entails high CHD risk. Noise shows a similar pattern. In contrast, physical workload entails a significant increase in SBP, and SBP is a key pathway to CHD risk.

Background:Shift work, noise, and physical workload are very common occupational exposures and they tend to cluster in the same groups of workers.Objectives:To study the short and long term effects of these exposures on risk of coronary heart disease (CHD) and to estimate the joint effects of these factors.Methods:The study population in this prospective 13 year follow up study of 1804 middle aged industrially employed men was collected at the first screening for the Helsinki Heart Study. The CHD end points (ICD-9 codes 410–414 and ICD-10 codes I20–I25) were obtained from official Finnish registers. The Finnish job-exposure matrix FINJEM provided information on occupational exposures. Relative risks (RR) of CHD for the exposures were estimated using Cox’s proportional hazard models adjusting for classical risk factors of CHD.Results:The RR in the five year follow up for continuous noise combined with impulse noise was 1.28; for shift work it was 1.59, and for physical workload 1.18, while in the 13 year follow up the RRs were 1.58, 1.34, and 1.31, respectively. When adjusted for white-collar/blue-collar status the RRs decreased markedly. The RR in the 13 year follow up for those exposed to two risk factors was close to 1.7 and for those exposed to all three, 1.87.Conclusion:Shift work and continuous noise entailed an excess risk for CHD in the shortest follow up with only a few retired workers but a decreasing risk during the longer follow up. For physical workload and impulse noise the trend was opposite: the CHD risk was increasing with increasing follow up time despite increasing numbers of retired workers.

Objectives The aim of the study was to investigate the short- and long-term effects of occupational exposure to continuous and impulse noise on the risk of CHD. Methods The effect of noise on CHD was studied among 6005 Finnish middle-aged industrially employed men (part of the screeners in the Helsinki Heart Study) in a prospective 18-year follow-up study. The CHD end points (codes 410-414 in the ninth revision of the International Classification of Diseases and codes I20-I25 in the tenth revision) were obtained from official Finnish registers. The Finnish job-exposure matrix FINJEM provided estimates of the proportion of exposed persons and the mean level of exposure among those exposed by occupation. The relative risks (RR) of CHD and the 95% confidence intervals (95% CI) for noise exposure were calculated from Cox’s proportional hazard models with adjustment for some other risk factors of CHD. Results The short-term (9-year follow-up) relative risk of CHD for the combined noise (continuous noise exceeding 80 decibels and impulse noise) was 1.38 (95% CI 1.04–1.82), and the long-term (18-year follow-up) RR was 1.54 (95% CI 1.28–1.86). For blue-collar workers the corresponding estimates were 1.11 (95% CI 0.82–1.51) and 1.29 (95% CI 1.05–1.57). Adjustment for other relevant risk factors did not materially change the results. Conclusions In our long-term follow-up of industrially employed men, exposure to noise, especially to impulse noise, was associated with a moderate, but statistically significant increase in CHD risk that persisted even after the workers had passed the age of retirement.