Finn Gyntelberg

Ventilation rates and health: multidisciplinary review of the scientific literature

UNLABELLED The scientific literature through 2005 on the effects of ventilation rates on health in indoor environments has been reviewed by a multidisciplinary group. The group judged 27 papers published in peer-reviewed scientific journals as providing sufficient information on both ventilation rates and health effects to inform the relationship. Consistency was found across multiple investigations and different epidemiologic designs for different populations. Multiple health endpoints show similar relationships with ventilation rate. There is biological plausibility for an association of health outcomes with ventilation rates, although the literature does not provide clear evidence on particular agent(s) for the effects. Higher ventilation rates in offices, up to about 25 l/s per person, are associated with reduced prevalence of sick building syndrome (SBS) symptoms. The limited available data suggest that inflammation, respiratory infections, asthma symptoms and short-term sick leave increase with lower ventilation rates. Home ventilation rates above 0.5 air changes per hour (h(-1)) have been associated with a reduced risk of allergic manifestations among children in a Nordic climate. The need remains for more studies of the relationship between ventilation rates and health, especially in diverse climates, in locations with polluted outdoor air and in buildings other than offices. PRACTICAL IMPLICATIONS Ventilation with outdoor air plays an important role influencing human exposures to indoor pollutants. This review and assessment indicates that increasing ventilation rates above currently adopted standards and guidelines should result in reduced prevalence of negative health outcomes. Building operators and designers should avoid low ventilation rates unless alternative effective measures, such as source control or air cleaning, are employed to limit indoor pollutant levels.

Serum selenium concentration and risk of ischaemic heart disease in a prospective cohort study of 3000 males.

Whether an association, causative or not, exists between the level of serum selenium and the risk of ischaemic heart disease (IHD) remains unsettled. We investigated the issue in a cohort of 3387 males aged 53-74 years (mean 63). Based on information about health status, life-style and socioeconomic factors given in a prefilled comprehensive questionnaire, the men were interviewed and the information validated. Following the interview, they underwent a clinical examination and had a venous blood sample drawn for the determination of a number of biochemical characteristics. Three hundred and forty-six men were excluded due to prevalent cardiovascular disease, including stroke. During the next three years (1986-1989) 107 men (approximately 3%) suffered an IHD event; 25 events were fatal. Compared to others, men with serum selenium levels less than or equal to 1 mumol/l, approximately the lowest tertile, had a 70% increased risk of IHD, relative risk (RR) with 95% confidence limits was 1.70 (1.14-2.53). After multivariate adjustment for cholesterol, social class, smoking and age, RR was 1.55 (1.00-2.39). Serum selenium level was significantly (P less than 0.05), but not strongly, correlated with a number of IHD risk factors: serum cotinine, tobacco smoking, social class, alcohol consumption, total cholesterol, hypertension, age and physical inactivity. Body mass index, HDL-cholesterol and triglycerides were not significantly associated with serum selenium. We conclude that middle-aged and elderly Danish men with serum selenium less than or equal to 1 mumol/l had a significantly increased risk of ischaemic heart disease. This association was not explained by the interrelationship of serum selenium and major cardiovascular risk factors.

Alcohol consumption, serum low density lipoprotein cholesterol concentration, and risk of ischaemic heart disease: six year follow up in the Copenhagen male study.

Abstract Objectives: To investigate the interplay between use of alcohol, concentration of low density lipoprotein cholesterol, and risk of ischaemic heart disease. Design: Prospective study with controlling for several relevant confounders, including concentrations of other lipid fractions. Setting: Copenhagen male study, Denmark. Subjects: 2826 men aged 53-74 years without overt ischaemic heart disease. Main outcome measure: Incidence of ischaemic heart disease during a six year follow up period. Results: 172 men (6.1%) had a first ischaemic heart disease event. There was an overall inverse association between alcohol intake and risk of ischaemic heart disease. The association was highly dependent on concentration of low density lipoprotein cholesterol. In men with a high concentration (>/=5.25 mmol/l) cumulative incidence rates of ischaemic heart disease were 16.4% for abstainers, 8.7% for those who drank 1-21 beverages a week, and 4.4% for those who drank 22 or more beverages a week. With abstainers as reference and after adjustment for confounders, corresponding relative risks (95% confidence interval) were 0.4 (0.2 to 1.0; P<0.05) and 0.2 (0.1 to 0.8; P<0.01). In men with a concentration <3.63 mmol/l use of alcohol was not associated with risk. The attributable risk (95% confidence interval) of ischaemic heart disease among men with concentrations >/=3.63 mmol/l who abstained from drinking alcohol was 43% (10% to 64%). Conclusions: In middle aged and elderly men the inverse association between alcohol consumption and risk of ischaemic heart disease is highly dependent on the concentration of low density lipoprotein cholesterol. These results support the suggestion that use of alcohol may in part explain the French paradox. Key messages Key messages The low risk of ischaemic heart disease in men with a low concentration of serum low density lipoprotein cholesterol was not modified by use of alcohol The risk of ischaemic heart disease in men with a high concentration of serum low density lipoprotein cholesterol was strongly modified by use of alcohol: those who did not drink alcohol had five times the risk of ischaemic heart disease compared with those who consumed three alcoholic beverages or more a day The results support the hypothesis that the apparent discrepancy between a low risk of ischaemic heart disease and a high intake of fat, a phenomenon known as the French paradox, may partly be explained by consumption of alcohol In studies of the use of alcohol and risk of ischaemic heart disease, serum low density lipoprotein cholesterol should be regarded as a potentially strong effect modifier not as a potential confounder

Shift work, social class, and ischaemic heart disease in middle aged and elderly men; a 22 year follow up in the Copenhagen Male Study.

OBJECTIVES: Shift work has been associated with an increased risk of ischaemic heart disease (IHD). Most published studies have had potential problems with confounding by social class. This study explores shift work as a risk factor for IHD after controlling for social class. METHODS: The Copenhagen male study is a prospective cohort study established in 1970-1 comprising 5249 men aged 40-59. Information obtained included working time, social class, and risk factors for IHD. A second baseline was obtained in 1985-6. The cohort was followed up for 22 years through hospital discharge registers for IHD, and cause of death was recovered from death certificates. RESULTS: One fifth of the cohort was shift working at entry with a significantly larger proportion of shift workers in lower social classes. Risk of IHD and all cause mortality over 22 years, adjusted for age only, for age and social class, and finally for age, social class, smoking, fitness, height, weight, and sleep disturbances, did not differ between shift and day workers. The relative risk of IHD, adjusted for age and social class was 1.0 (95% confidence interval (95% CI) 0.9-1.2). Men being shift workers in both 1971 and 1985 had the same risk as ex-shift workers in an 8 years follow up from the 1985-6 baseline. CONCLUSIONS: The present study questions shift work as an independent risk factor for IHD. The results of the study emphasise the importance of controlling adequately for the interplay of shift work and social class.

High Triglycerides and Low HDL Cholesterol and Blood Pressure and Risk of Ischemic Heart Disease

Treatment of high blood pressure (BP) has not produced the expected reduction in risk of ischemic heart disease (IHD). Subjects with high BP often have the metabolic syndrome X, an aggregation of abnormalities in glucose and lipid metabolism. We tested the hypothesis that the BP level would be less predictive of risk of IHD in those with high triglycerides (TG) and low HDL cholesterol (HDL-C), the characteristic dyslipidemia in the metabolic syndrome than in those without. Baseline measurements of fasting lipids, systolic BP (SBP), diastolic BP (DBP), and other risk factors were obtained in 2906 men, age 53 to 74 years, free of overt cardiovascular disease. High TG/low HDL-C was defined as TG >1.59 mmol/L and HDL-C <1.18 mmol/L. Within an 8-year period, 229 men developed IHD. In men with high TG/low HDL-C, the incidence of IHD according to SBP (<120, 120 to 140, >140 mm Hg) was 12.5%, 12.9%, and 10.0% (P=NS), respectively, and according to DBP, the incidence of IHD was (<75, 75 to 90, >90 mm Hg) 13.7%, 10.6%, and 13.7% (P=NS), respectively. The corresponding figures for other men were 5.2%, 8. 0%, and 9.7% for SBP (P<0.001), and 6.1%, 7.5%, and 9.9% for DBP (P<0.03). In conclusion, the BP level did not predict the risk of IHD in those with high TG/low HDL-C. This finding may explain the reason lowering BP has not produced the expected reduction in IHD.

Alcohol consumption, Lewis phenotypes, and risk of ischaemic heart disease

We have previously found an increased risk of ischaemic heart disease (IHD) in men with the Lewis phenotype Le(a-b-) and suggested that the Lewis blood group has a close genetic relation with insulin resistance. We have investigated whether any conventional risk factors explain the increased risk in Le(a-b-) men. 3383 men aged 53-75 years were examined in 1985-86, and morbidity and mortality during the next 4 years were recorded. At baseline, we excluded 343 men with a history of myocardial infarction, angina pectoris, intermittent claudication, or stroke. The potential risk factors examined were alcohol consumption, physical activity, tobacco smoking, serum cotinine, serum lipids, body-mass index, blood pressure, prevalence of hypertension and non-insulin-dependent diabetes mellitus, and social class. In 280 (9.6%) men with Le(a-b-), alcohol was the only risk factor significantly associated with risk of IHD. There was a significantly inverse dose-effect relation between alcohol consumption and risk; trend tests, with adjustment for age, were significant for fatal IHD (p = 0.02), all IHD (p = 0.03), and all causes of death (p = 0.02). In 2649 (90.4%) men with other phenotypes, there was a limited negative association with alcohol consumption. In Le(a-b-) men, a group genetically at high risk of IHD, alcohol consumption seems to be especially protective. We suggest that alcohol consumption may modify insulin resistance in Le(a-b-) men.

Occupational and leisure time physical activity: risk of all-cause mortality and myocardial infarction in the Copenhagen City Heart Study. A prospective cohort study

Objectives Men with low physical fitness and high occupational physical activity are recently shown to have an increased risk of cardiovascular disease and all-cause mortality. The association between occupational physical activity with cardiovascular disease and all-cause mortality may also depend on leisure time physical activity. Design A prospective cohort study. Setting The Copenhagen City Heart Study. Participants 7819 men and women aged 25–66 years without a history of cardiovascular disease who attended an initial examination in the Copenhagen City Heart Study in 1976–1978. Outcome measures Myocardial infarction and all-cause mortality. Occupational physical activity was defined by combining information from baseline (1976–1978) with reassessment in 1981–1983. Conventional risk factors were controlled for in Cox analyses. Results During the follow-up from 1976 to 1978 until 2010, 2888 subjects died of all-cause mortality and 787 had a first event of myocardial infarction. Overall, occupational physical activity predicted all-cause mortality and myocardial infarction in men but not in women (test for interaction p=0.02). High occupational physical activity was associated with an increased risk of all-cause mortality among men with low (HR 1.56; 95% CI 1.11 to 2.18) and moderate (HR 1.31; 95% CI 1.05 to 1.63) leisure time physical activity but not among men with high leisure time physical activity (HR 1.00; 95% CI 0.78 to 1.26) (test for interaction p=0.04). Similar but weaker tendencies were found for myocardial infarction. Among women, occupational physical activity was not associated with subsequent all-cause mortality or myocardial infarction. Conclusions The findings suggest that high occupational physical activity imposes harmful effects particularly among men with low levels of leisure time physical activity.

Long work hours and physical fitness: 30-year risk of ischaemic heart disease and all-cause mortality among middle-aged Caucasian men

Background No previous long-term studies have examined if workers with low physical fitness have an increased risk of cardiovascular mortality due to long work hours. The aim of this study was to test this hypothesis. Methods The study comprised 30-year follow-up of a cohort of 5249 gainfully employed men aged 40–59 years in the Copenhagen Male Study. 274 men with cardiovascular disease were excluded from the follow-up. Physical fitness (maximal oxygen consumption, Vo2max) was estimated using the Åstrand bicycle ergometer test, and number of work hours was obtained from questionnaire items; 4943 men were eligible for the incidence study. Results 587 men (11.9%) died because of ischaemic heart disease (IHD). Cox analyses adjusted for age, blood pressure, smoking, alcohol, body mass index, diabetes, hypertension, physical work demands, and social class, showed that working more than 45 h/week was associated with an increased risk of IHD mortality in the least fit (Vo2max range 15–26; HR 2.28, 95% CI 1.10 to 4.73), but not intermediate (Vo2max range 27–38; HR 0.94, 95% CI 0.59 to 1.51) and most fit men (Vo2max range 39–78; HR 0.91, 95% CI 0.41 to 2.02) referencing men working less than 40 h/week. Conclusions The findings indicate that men with low physical fitness are at increased risk for IHD mortality from working long hours. Men working long hours should be physically fit.

Does the benefit on survival from leisure time physical activity depend on physical activity at work? A prospective cohort study.

Purpose To investigate if persons with high physical activity at work have the same benefits from leisure time physical activity as persons with sedentary work. Methods In the Copenhagen City Heart Study, a prospective cohort of 7,411 males and 8,916 females aged 25–66 years without known cardiovascular disease at entry in 1976–78, 1981–83, 1991–94, or 2001–03, the authors analyzed with sex-stratified multivariate Cox proportional hazards regression the association between leisure time physical activity and cardiovascular and all-cause mortality among individuals with different levels of occupational physical activity. Results During a median follow-up of 22.4 years, 4,003 individuals died from cardiovascular disease and 8,935 from all-causes. Irrespective of level of occupational physical activity, a consistently lower risk with increasing leisure time physical activity was found for both cardiovascular and all-cause mortality among both men and women. Compared to low leisure time physical activity, the survival benefit ranged from 1.5–3.6 years for moderate and 2.6–4.7 years for high leisure time physical activity among the different levels of occupational physical activity. Conclusion Public campaigns and initiatives for increasing physical activity in the working population should target everybody, irrespective of physical activity at work.

Sleep Duration and Ischemic Heart Disease and All-Cause Mortality: Prospective Cohort Study on Effects of Tranquilizers/hypnotics and Perceived Stress

OBJECTIVES This prospective study aimed to examine if sleep duration is a risk indicator for ischemic heart disease (IHD) and all-cause mortality, and how perceived stress during work and leisure time and use of tranquilizers/hypnotics modifies the association. METHOD A 30-year follow-up study was carried out in the Copenhagen Male Study comprising 5249 men (40-59 years old). Confounders included lifestyle factors (smoking, alcohol, and leisure-time physical activity), clinical and health-related factors (body mass index, blood pressure, diabetes, hypertension, and physical fitness) and social class. Men with a history of cardiovascular disease at baseline were excluded. RESULTS During follow-up, 587 men (11.9%) died from IHD and 2663 (53.9%) due to all-cause mortality. There were 276 short (<6 hours), 3837 medium (6-7 hours), and 828 long (≥8 hours) sleepers. Men who slept <6 hours had an increased risk of IHD mortality but not all-cause mortality, when referencing medium sleepers. Perceived psychological pressure during work and leisure was not a significant effect modifier for the association between sleep duration and IHD mortality. In contrast, among men using tranquilizers/hypnotics (rarely or regularly), short sleepers had a two-to-three fold increased risk of IHD mortality compared to medium sleepers. Among those never using tranquilizers/hypnotics, no association was observed between sleep duration and IHD mortality. CONCLUSION Short sleep duration is a risk factor for IHD mortality among middle-aged and elderly men, particularly those using tranquilizers/hypnotics on a regular or even a rare basis, but not among men not using tranquilizers/hypnotics.