Gil Harari

Association of Calcitriol and Blood Pressure in Normotensive Men

The purpose of this study was to clarify the possible associations between the serum 1,25-dihydroxyvitamin D (calcitriol) level and blood pressure. Cross-sectional analysis of data was performed. Data collected included levels of serum calcitriol, parathyroid hormone, serum calcium, and blood lead; blood pressure; dietary history; and demographic and anthropometric variables. One hundred normotensive male industrial employees made up the study population. Systolic blood pressure and diastolic blood pressure were main outcome measures. After possible confounders were controlled for, multivariate analyses yielded an inverse, independent, and statistically significant association between calcitriol level and systolic blood pressure (standardized beta= -0.2704, P=.0051). A similar trend of borderline significance was found for the association between calcitriol and diastolic blood pressure (standardized beta= -0.1814, P=.0611). Parathyroid hormone, serum calcium, and blood lead levels were not associated with blood pressure. When subjects were divided into four groups by calcitriol level, those in the lowest quartile showed significantly higher systolic and diastolic blood pressures than those in the upper quartile (difference=11 mmHg, P=.007, and difference=4 mmHg, P=.071, respectively). There is an inverse association between serum calcitriol level and blood pressure. This suggests that in addition to its role in calcium homeostasis, the active metabolite of vitamin D may play a role in determining blood pressure. The differences in both systolic and diastolic blood pressures between the upper and lower quartiles of serum calcitriol were substantial and may be of clinical significance.

Changes in dietary intake account for seasonal changes in cardiovascular disease risk factors.

Objectives: (1) to compare dietary intake in summer and winter time; (2) to measure the change in body mass index (BMI), blood pressure and serum cholesterol between winter and summer; and (3) to determine the relationships between seasonal differences in dietary intake and BMI, blood pressure and serum cholesterol measurements.Subjects and methods: Ninety-four male industrial employees were screened twice in one year, in their work place, at winter and summer time. Workers were recruited from two factories and response rate was 95%. Health-related variables, including dietary intake, blood pressure and serum cholesterol were evaluated at each season and were compared. Correlation coefficients between seasonal differences in dietary intake and in BMI, blood pressure and serum cholesterol were calculated.Results: From summer to winter the mean values of BMI increase from 26.1 kg/cm2 to 26.6 (P=0.038), systolic blood pressure from 119.6 to 121.6 (P=0.025), diastolic blood pressure from 75.2 to 77.2 mmHg (P=0.001), total cholesterol from 200.8 to 208.6 mg/dL (P=0.001), LDL cholesterol from 125.2 to 134.9 (P=0.001) and HDL cholesterol from 42.7 to 44.3 (P=0.0084). Triglycerides levels decrease from 174 to 145 in the winter (P=0.03). Mean dietary intake of fat increases from 99.1 to 106.0 (P=0.0016), saturated fat from 43.6 to 46.3 (P=0.0137), polyunsaturated fat from 25.1 to 28.3 (P=0.0002), cholesterol from 462.0 to 497.9 (P=0.0313), sodium from 5778.5 to 8208.2 (P=0.0035), zinc from 11.6 to 12.3 (P=0.0001), vitamin B1 from 1.4 to 1.5 (P=0.002), vitamin D from 4.3 to 4.9 (P=0.0323) and vitamin E from 11.2 to 12.7 (P=0.0073). Significant correlation was shown between the seasonal increase in saturated fat and the increase in BMI (r=0.37), total cholesterol (r=0.21) and LDL cholesterol (r=0.29). Seasonal change in dietary cholesterol intake was significantly and positively correlated with serum total cholesterol (r=0.24) and LDL cholesterol (r=0.24). Blood pressure was not associated with nutritional intake variables.Conclusions: Dietary intake in summer and winter is different as well as blood pressure, BMI and serum cholesterol. The seasonal increase in fat and cholesterol intake at winter time is associated with changes in BMI and serum cholesterol.Sponsorship: The study was supported by the committee for preventive Action and Research in Occupational Health, the Ministry of Labor and Social Affairs, Jerusalem, Israel.Guarantor: Dr Estela Kristal-Boneh.

A PROSPECTIVE STUDY OF THE EFFECTS OF CHANGES IN SMOKING HABITS ON BLOOD COUNT, SERUM LIPIDS AND LIPOPROTEINS, BODY WEIGHT AND BLOOD PRESSURE IN OCCUPATIONALLY ACTIVE MEN. THE ISRAELI CORDIS STUDY

In cross-sectional studies, significant differences in cardiovascular disease risk factors have been observed between smokers and non-smokers. The aim of this study was to examine the effects of smoking initiation and cessation on these factors in a population-based prospective study. 987 male employees in Israeli industry underwent health screening in the CORDIS study and were re-examined an average of two and a half years later. We examined the associations between smoking initiation and cessation and changes in blood count, serum lipids and lipoproteins, body weight and blood pressure. After adjusting for potential confounders, smoking cessation was associated with significant decreases in leukocyte count, hemoglobin and hematocrit whereas smoking initiation resulted in increased leukocyte count. There were moderate, non-significant increases in both serum HDL cholesterol (HDL-C) and LDL-C, and a slight decrease in serum triglycerides. Blood pressure remained essentially unchanged, despite the fact that smoking cessation resulted in a significant weight increase and smoking initiation in a significant decline in weight. These findings demonstrate that changes in smoking habits result in fairly rapid changes in blood count and body weight, but have much smaller effects on serum lipids and blood pressure.

Association of physical activity at work with mortality in Israeli industrial employees: the CORDIS study.

The objective of this study was to evaluate the association of physical activity at work with the risk of all-cause cardiovascular disease and cancer mortality. The cohort consisted of 3488 male, Israeli, industrial employees who participated in an 8-year follow-up study. During this period 129 deaths were recorded: 54 from cardiovascular disease, 47 from cancer, and 28 from other causes. Physical activity at work was assessed at entry on a 4-point scale (none, light, medium, and high). Potential confounding demographic, anthropometric, and socioeconomic variables, and health habits including leisure time physical activity were accounted for. We found that the hazard ratio of all-cause mortality in workers with a high physical workload was 1.82 (95% confidence interval, 1.18 to 2.81) compared with workers having a low workload. A similar trend was noted for cardiovascular disease and cancer mortality. We concluded that a high physical workload is associated with increased mortality rates. Future studies should differentiate between leisure time and work time physical activity.

Seasonal change in 24-hour blood pressure and heart rate is greater among smokers than nonsmokers

In general, blood pressure is higher in winter than in summer, and this factor may be partly responsible for the higher mortality from cardiovascular disease in winter. Cigarette smoking causes an acute pressor response that may interact with this cardiovascular response to cold exposure. We sought to determine whether the seasonal variation in blood pressure and heart rate differs between cigarette smokers and nonsmokers. We evaluated 24-hour ambulatory systolic blood pressure (SBP), ambulatory diastolic blood pressure (DBP), and ambulatory heart rate of 97 healthy men (73 nonsmokers and 24 smokers), 28 to 63 years of age, during the summer and winter, taking indoor temperatures into consideration. Smokers and nonsmokers both had higher daytime ambulatory SBPs and DBPs in winter than in summer (after adjustment for potential confounders). However, the winter increase seen in the smokers was significantly higher for mean daytime SBP (7.3 versus 2.7 mm Hg, P<.01), for mean daytime DBP (4.4 versus 3.1 mm Hg, P=.051), and for ambulatory heart rate (3.9 versus -1.7 beats/min, P<.001). The double product increased from summer to winter (daytime) by 10.53 for smokers and by only 0.11 for nonsmokers (P<.01). There was an independent interaction between season and smoking status that affected SBP (standardized beta=0.66, P<.0001) and DBP (standardized beta=0.32, P<.0001). Smokers have a greater seasonal variation in blood pressure and heart rate than nonsmokers and show a larger increase in the cardiovascular load in winter. Smoking apparently potentiates the cardiovascular response to various climatic conditions. Season should be taken into account in studies of blood pressure and in the diagnosis and treatment of hypertension, particularly among cigarette smokers.

Summer-Winter Differences in 24 h Variability of Heart Rate:

Objective To examine possible seasonal changes in heart rate variability (HRV). Background Greater than normal mortality from cardiovascular disease (CVD) in the winter has been reported for many countries and might be partly explained by considering seasonal changes in CVD risk factors. Depression of HRV is an independent predictor of arrhythmic complications and of cardiac death, and it is also among the variables that may be affected by the season of the year. Methods We compared pairs of 24 h HRV data of 120 healthy men who were examined once in the summer and once in the winter. Multivariate analyses were performed for each dependent variable (HRV indexes) in separate statistical models with age, resting heart rate, serum level of cholesterol, cigarette smoking, body mass index, sports habits, alcohol consumption, systolic blood pressure, physical activity at work, years of education, consumption of energy, and season as the independent variables. Results Although there were no seasonal differences in mean R–R interval, all indexes of HRV were found to be lower in the summer than they were during winter. Differences and 95% confidence intervals were standard deviation (SD) of coupling intervals between normal beats 12 ms, 6–17 ms; SD of 5 min mean R–R intervals 14 ms, 8–20 ms; mean of all 5 min SD of R-R intervals 2.0 ms, 0.6–2.5 ms; proportion of adjacent R-R intervals differing by > 50 ms 1.5%, 0.6–2.5% and root mean square of the difference between successive normal intervals 3.1 ms, 1.5–4 ms. Multivariate analyses showed that HRV in the winter was less than that in the summer even after adjustment for age, serum level of cholesterol, systolic blood pressure, and body mass index. Conclusions HRV indexes of healthy men vary physiologically by season, with lowest values obtained in the winter. Since low HRV is linked to pathologic conditions, the significance of seasonal changes for those suffering from CVD and their possible contribution to the greater mortality rates in winter have to be considered.

Acute and Chronic Effects of Noise Exposure on Blood Pressure and Heart Rate among Industrial Employees: The Cordis Study

The effects of industrial noise on resting heart rate and blood pressure were studied in 3,105 blue-collar workers. Heart rate and blood pressure were measured in different workers at various times during the workday. After controlling for several possible confounders, we found that resting heart rate in females was associated positively with noise intensity (p = .036) and with time of day (p = .054). In males, resting heart rate was associated with noise intensity; however, such association was related to time of day (p = .046). No such associations were found for blood pressure in either sex. We plotted the mean resting heart rate by time of day for workers exposed to high [ > or = 80 db(A)] and low noise, and no difference was evident with respect to morning heart rate in either sex. After 4 h of noise exposure for males (and less time for females), individuals who were exposed to high noise had higher heart rates; however, in females this was not observed at the end of the workday. Thus, recurrent daily exposure to high noise at work has an acute, though not residual, effect on resting heart rate.

Body Mass Index is Associated with Differential Seasonal Change in Ambulatory Blood Pressure Levels

Seasonal changes in blood pressure may be partially explained in thermoregulatory terms. We hypothesized that the seasonal variation in blood pressure is related to body mass index, due to the increased thermoregulatory requirements of leaner individuals. Ambulatory systolic and diastolic blood pressure were monitored once each in summer and winter in 101 healthy normotensive men aged 28 to 63 years. Environmental conditions and body mass index were measured. The population was divided according to quartiles of body mass index. The percentage of subjects with systolic blood pressure increases of more than 10 mm Hg from summer to winter was highest among subjects in the lowest body mass index category, and lowest among those in the highest body mass index category (35% and 8%, respectively, P < .0001). After adjusting for possible confounders, the change in mean systolic blood pressure from summer to winter was inversely associated with body mass index (beta = -0.26, P = .0149). There was no association between diastolic blood pressure change and body mass index. The increase in systolic blood pressure from summer to winter is inversely and independently associated with body mass index. Hypertension research and epidemiological blood pressure studies should take into account the interaction between season, body mass index, and blood pressure. It may also be important to assess hypertension and response to antihypertensive treatment in relation to season, particularly in lean hypertensives.

Seasonal changes in ambulatory blood pressure in employees under different indoor temperatures

OBJECTIVE--The effect of indoor temperature control on summer and winter ambulatory blood pressure levels at work was studied. METHOD--Ambulatory systolic blood pressure (SBP) and diastolic blood pressure (DBP) were monitored once in summer and once in winter in 101 healthy normotensive subjects aged 28-63 years, engaged in similar physical work, from two plants with and three without air conditioning. Subjects were interviewed about health related habits, and measurements of environmental and occupational conditions were obtained. RESULTS--After controlling for possible confounders, mean SBP and DBP during work were significantly higher in winter than in summer (delta SBP = 3.4 mm Hg, P = 0.035; delta DBP = 3.3 mm Hg, P < 0.003). The seasonal change in SBP and DBP showed an independent association with the presence or absence of air conditioning of the industrial plants (SBP: beta = 0.194, P < 0.0001; DBP: beta = 0.054, P = 0.038). The percentage of subjects with increases of more than 10 mm Hg from summer to winter was higher in plants without than with air conditioning. CONCLUSIONS--(1) In normotensive subjects ambulatory working BP varies by season, with higher values in winter. If validated for hypertensive subjects, it may be necessary to tailor drug treatment to these variations. (2) The findings make it clear that drawing valid conclusions from comparisons of BPs between groups requires controlling for several factors, particularly season of the year. (3) Climatic conditions in the industrial plant influence the magnitude of seasonal variations in BP. Work in plants without air conditioning places a considerable added load on the employees cardiovascular system.

Circannual Variations in Blood Cholesterol Levels

The seasonality of blood cholesterol is still not well established. Some have described a seasonal pattern with highest levels during autumn and lowest in summer, whereas others have reported no change. A number of studies showed circannual variations with maximum levels in winter and minimum in summer. The aim of this study was to examine the circannual variation of cholesterol in a large cohort in Israel. In the Israeli CORDIS study, employees of 21 factories were screened for cardiovascular disease risk factors during 1985-7. As part of the information gathered, serum cholesterol and blood counts were available for 3,726 men and 1,514 women. Serum cholesterol levels fit a circannual rhythm assessed by the cosinor analysis. Highest levels of serum cholesterol were found in spring and lowest in summer. We conclude that there is a circannual change of serum cholesterol, which could be partially associated with changes in environmental temperature. The circannual variation in serum cholesterol was considerable and should be taken into account when carrying out clinical evaluation of patients.