In the Helsinki Heart Study, a randomized five-year, double-blind trial, a 34% reduction in the incidence of coronary heart disease (CHD) was observed in dyslipidemic men treated with gemfibrozil. Averaged over the five years of the trial, gemfibrozil therapy produced, compared with placebo, mean decreases of 10% in serum total cholesterol level, 14% in non-high-density lipoprotein (HDL) cholesterol level, 11% in low-density lipoprotein (LDL) cholesterol level, 35% in triglyceride level, and a mean increase of 11% in HDL cholesterol level from baseline levels measured prior to treatment. While changes in HDL cholesterol level were similar in all Fredrickson types, the effect on concentrations of total cholesterol and LDL cholesterol was largest in type IIA and on LDL minimal in type IV. The reduction of CHD incidence over placebo was largest in type IIB and smallest in type IIA. The lipid changes were dependent on lipid levels prior to treatment and on compliance with the medication regimen. When risk factors for CHD, including age, blood pressure, smoking and drinking habits, baseline lipid levels, and exercise and relative weight, were controlled by applying the Cox proportional hazards model, the changes in serum HDL and LDL cholesterol levels were both statistically significantly associated with the decline in CHD incidence within the gemfibrozil-treated group. The large decrease in serum triglyceride levels had relatively small effect on CHD incidence. Thus, the results of this study, together with earlier observations, suggest that both elevating HDL and lowering LDL cholesterol levels are effective in the primary prevention of CHD.
Objectives The combined effects of age, leisure-time physical activity, smoking, alcohol consumption, and different forms of shift work on the prevalence of sleep compIaints and daytime sleepiness were studied among workers in industly, transport, and traffic. Methods Altogether 3020 subjects were studied using a psychosocial questionnaire. The participants were currently employed men, aged 45-60 years, from a postal and telecommunication agency, the railway company, and 5 industrial companies. On the basis of a factor analysis of an 1 I-item sleep questionnaire, the sleep complaints were grouped into the categories of insomnia, sleep deprivation, daytime sleepiness, and snoring. The importance of the shift schedule, age, and lifestyle factors as simultaneous predictors of the complaints was studied in a logistic regression analysis and an analysis of covariance. Results The prevalence of insomnia, sleep deprivation, and daytime sleepiness depended significantly on the shift system. All sleep complaints were more common in 2-and 3-shift work and in irregular shift work than in day work. The prevalence of daytime sleepiness was 20-37%, depending on the shift system. Leisure-time physical activity and alcohol consumption were the most important lifestyle factors predicting all sleep complaints, except snoring. The effects of physical activity and alcohol consumption differed for different shift schedules. C O~~C~U S~O~~S Different shift systems, also 2-shift work and permanent night work, seem to increase the frequency of sleep complaints. Especially 3-shift work seems to interact with lifestyle factors by increasing the adverse effects and decreasing the beneficial effects on sleep and sleepiness.
Objectives The joint effect of shift work and certain adverse life-style factors on coronary heart disease (CHD) was studied. Methods Base-line measurements were obtained for a 6-year follow-up of an industrially employed cohort (N=1806), whose shiftwork status was recorded from a questionnaire filled out by a sample of the cohort. The CHD end points (codes 4 1 0 4 1 4 of the 9th revision of the International Classification of Diseases) were obtained from official Finnish registers. In order that the joint effects of shift work and life-style factors on the risk of CHD could be studied, dichotomized variables and their combinations as a dummy variable system in Cox's proportional hazards models were used. Results The relative risks were 1, 1.6 [95% confidence interval (95% CI) 1.1-2.51, 1.3 (95% CI 0.9-2.1), and 2.7 (95% CI 1 . 8 4 . 1 ) for the following combinations of shift work (SW) and smoking (SM): SW-&SM-, SW-&SM+, SW+&SM-, and SW+&SM+, respectively; and the corresponding figures for shift work and obesity (BMI 228 kg/m2) were 1,1.2 (95% CI0.8-1.9), 1.3 (95% CI0.9-1.9), and 2.3 (95% CI 1.5-3.6), respectively. Inboth cases the effect was at least multiplicative. For the shift workers the relative risk for CHD rose gradually with increasing numbers of adverse life-style factors, but for the day workers there was no clear dose-response pattern. C O~C~U S~O~S Shift work seems to trigger the effect of other, lifestyle-related risk factors of CHD and therefore calls for active prevention among shift workers.
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...
The Helsinki Heart Study is a coronary primary prevention trial in a group of middle aged men with lipid abnormalities. Its aim is to investigate the effects on the incidence of coronary heart disease of simultaneously lowering serum total and low density lipoprotein (LDL)-cholesterol and elevating high density lipoprotein (HDL)-cholesterol with gemfibrozil, over a period of 5 years. Participants were selected from a population of 23 531 men between 40 and 55 years of age. The mean serum total cholesterol among 18 966 screened subjects was 6.3 mmol l-1 (245 mg dl-1) and the mean HDL-cholesterol 1.3 mmol l-1 (50.3 mg dl-1). All subjects meeting the lipid acceptance criterion of non-HDL-cholesterol (i.e. total cholesterol minus HDL-cholesterol) greater than 5.2 mmol l-1 (200 mg dl-1) on two separate occasions two to three months apart, who were free from coronary heart disease or other major illness, were invited to participate. The total cholesterol level for the final 4081 study participants was 7.5 mmol l-1 (290 mg dl-1) and HDL-cholesterol was 1.23 mmol l-1 (47.6 mg dl-1). Mean systolic and diastolic blood pressures were 141.7 and 91.3 mmHg. About 15% of participants were hypertensive and 36% were smokers. A total of 2051 men were randomly allocated to receive gemfibrozil 600 mg twice daily and 2030 matching placebo capsules. A cholesterol-lowering diet was also prescribed for all participants. The randomized treatment groups were well balanced. Equal distribution of major risk factors was achieved in relevant sub-groups. This report describes the procedures involved in setting up the study, summarizes the baseline data obtained and reviews the success of the randomization procedure. Finally, it compares the design of this study with that of some other major preventive trials.
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