Association of Lifestyle with Serum Lipid Levels : a Study of Middle-Aged Japanese Men

Cross-sectional associations between lifestyle and serum lipid levels were examined in 1591 Japanese male office workers aged 35 to 59 years in Osaka, Japan. From multiple linear regression analyses, significant correlates with low-density lipoprotein (LDL) cholesterol, highdensity lipoprotein (HDL) cholesterol, and Log triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol were, in the order of relative importance: BMI, alcohol intake (negative) and age for LDL cholesterol level; BMI (negative), cigarette smoking (negative), alcohol intake, consideration for nutritional balance, hours of brisk walking, hours of walking at an ordinary pace and physical exercise for HDL cholesterol level; BMI, cigarette smoking, consideration for nutritional balance (negative), hours of work (negative), alcohol intake and coffee drinking (negative) for Log triglyceride level; and BMI, alcohol intake (negative), cigarette smoking, consideration for nutritional balance (negative), age, hours of brisk walking (negative) and the frequency of snack intake between meals for the ratio of LDL cholesterol to HDL cholesterol. Our data suggest that obesity, cigarette smoking and snack intake between meals are atherogenic whereas alcohol consumption, consideration for nutritional balance and walking long hours, especially at a brisk pace, are anti-atherogenic in middle-aged Japanese men. J Epidemiol, 2000 ; 10 : 216-225.


MATERIALS AND METHODS
A survey to evaluate lifestyle factors related to serum lipid profiles was conducted in 1994 among employees of T Corporation, which is one of the biggest building contractors in Osaka, Japan.The surveillance population in May 1994 consisted of 1580 Japanese male office workers aged 35 to 59 years, and the participation rate was 99.9%.
The survey included a questionnaire on lifestyle, physical examinations and collection of blood samples for laboratory analysis.Data on lifestyle were obtained by interview.Selected items of lifestyle for this study were as follows: overall obesity, alcohol intake, cigarette smoking, eating breakfast, snack intake between meals, physical exercise, hours of sleep, consideration for nutritional balance, hours of work, coffee drinking and hours of walking at an ordinary pace and/or at a brisk pace.The former seven items of lifestyle have been identified as healthy lifestyle indices in the studies of Belloc and Breslow 21) and the following two items (consideration for nutritional balance and hours of work) have been recommended by Morimoto et al.22), composed of eight items on healthy lifestyle for use in a study in Japan, based on that of Belloc and Breslow.Body mass index (BMI) was used as a measure of overall obesity.Weight and height were measured with the subjects wearing typical indoor clothing but with their shoes off, and BMI was calculated as weight/height 2(kg/m2).Alcohol intake was obtained by interview as usual weekly intake of alcohol in go (a traditional Japanese unit of volume corresponding to 23 g ethanol) and converted to grams of ethanol per day.One go is 180 ml of sake and corresponds to one bottle of beer (633 ml), two shots (70 ml) of whisky, or two glasses (180 ml) of wine.As for coffee drinking, examinees were asked their usual daily intake in cups, but information on the brewing method of coffee was not collected.Information of walking hours was based on the following question: *How long do you usually walk at an ordinary pace (4 kilometers an hour on average for Japanese) and/or at a brisk pace a day, except for working hours?', which could be answered in minutes.Nineteen subjects were under medication for dyslipidemia, and the remaining 1561 subjects constituted the study population.Data on lifestyle were grouped into three subgroups as shown in Table 1.Fasting blood samples were drawn from an antecubital vein.Serum total cholesterol, HDL cholesterol and triglyceride were analyzed with Olympus AU-5000 (Olympus Japan Co., Ltd., Tokyo, Japan) by the Nihon Clinical Laboratories Inc. (Tokyo, Japan).The level of LDL cholesterol was calculated from total cholesterol, HDL cholesterol and triglyceride using Friedewald's formula (LDL cholesterol = total cholesterol -HDL cholesterol -triglyceride/5) in the subjects whose serum triglyceride level was < 400 mg/dl 23).The triglyceride value was * 400 mg/dl in 42 subjects (2.7%), and we excluded these cases showing this value from statistical analysis involving LDL cholesterol.
For statistical assessment, analysis of covariance was used to compare the age-adjusted means of serum lipids among the three subgroups of lifestyle.Stepwise multiple regression analyses were performed to examine an independent association of lifestyle factors and their relative importance as determinants of serum lipids.In the statistical analyses, the logarithm for the triglyceride (because of the non-gaussian distribution of the frequency for this variable) was used.
Data analysis was performed with the SPSS/PC statistical package (Marija J. Norusis, SPSS Inc., Chicago, IL, USA).All reported p-values are two-tailed and a p-value of less than 0.05 was considered significant.

RESULTS
Characteristics of the study subjects are summarized in Table 1.The mean values of LDL cholesterol and HDL cholesterol levels and the ratio of LDL cholesterol to HDL cholesterol were 116.6 mg/dl (standard deviation; 28.7 mg/dl), 53.3 mg/dl (12.0 mg/dl) and 2.29 (0.78), respectively.The frequency distributions of LDL cholesterol and HDL cholesterol levels and the ratio of LDL cholesterol to HDL cholesterol showed unimodal curves with medians of 114.4 mg/dl, 53 mg/dl and 2.19, respectively.The mean Log triglyceride level was 4.72 mg/dl with the standard deviation of 0.59 mg/dl, and the frequency distribution of Log triglyceride showed some skewing to the right with a median of 4.64 mg/dl.There were no definite differences in lifestyle between all 1561 subjects of this study and 1519 subjects whose LDL cholesterol levels were available for.
The age-adjusted means of LDL cholesterol, HDL cholesterol and Log triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol by lifestyle are shown in Table 2. Age-adjusted means of LDL cholesterol level were significantly different among the three subgroups of BMI, alcohol intake, cigarette smoking, eating breakfast and snack intake between meals.LDL cholesterol levels increased with an increase in BMI or with the increased frequency of snack intake between meals.Age-adjusted means of LDL cholesterol level were lower in those who drank alcohol daily than in those who did not, and were also lower in those who smoked currently than in those who did not.Age-adjusted means of LDL cholesterol level were higher in those who ate breakfast sometimes or everyday than in those who did not.
Age-adjusted means of HDL cholesterol differed significantly among the three subgroups of BMI , alcohol intake, cigarette smoking, snack intake between meals, consideration for nutritional balance, coffee drinking, hours of walking at an ordinary pace or at a brisk pace and physical exercise.Age-adjusted means of HDL cholesterol decreased with an increase in BMI , cigarette smoking, or the frequency of snack intake between meals.On the other hand, age-adjusted means of HDL cholesterol increased with an increase in alcohol intake, consideration In parentheses are the percentages of men whose LDL cholesterol were available for.
for nutritional balance or the frequency of physical exercise.Age-adjusted means of HDL cholesterol were lower in those who consumed 3 cups/day of coffee or more than in those who consumed coffee hardly ever or who consumed less than 3 cups/day of coffee.Furthermore, age-adjusted means of HDL cholesterol were lower in those who walked at an ordinary pace or at a brisk pace less than 0.5 hours a day than in those who walked an ordinary pace or at a brisk pace 0.5 hours a day or more.
As for the Log triglyceride level, age-adjusted means of Log triglyceride level were significantly different among the three subgroups of BMI, alcohol intake, cigarette smoking, consideration for nutritional balance and hours of work.Log triglyceride levels increased with increasing BMI and cigarette smoking.The subjects who drank 46 .0g/day of ethanol or more had the higher levels of Log triglyceride than those who did not Table 2. Age-adjusted means of LDL cholesterol, HDL cholesterol and Log triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol according to lifestyle factors in 1561 Japanese male office workers.
*Data for LDL cholesterol were available for 1519 men .
Analysis of covariance was used to compare the age-adjusted means of serum lipid and lipoprotein levels among the three subclasses.
drink alcohol or who drank less than 46.0 g/day of ethanol.Log triglyceride levels decreased with an increase in working hours.
Age-adjusted ratios of LDL cholesterol to HDL cholesterol differed significantly among the three subgroups of BMI, alcohol intake, cigarette smoking, snack intake between meals, coffee drinking and hours of brisk walking.Age-adjusted ratios of LDL cholesterol to HDL cholesterol increased with an increase in BMI, cigarette smoking, or the frequency of snack intake between meals.On the other hand, age-adjusted ratios of LDL cholesterol to HDL cholesterol decreased with an increase in alcohol intake.Age-adjusted ratios of LDL cholesterol to HDL cholesterol were lower in those who consumed 3 cups/day of coffee or more than in those who consumed coffee hardly ever or who consumed less than 3 cups/day of coffee, and were higher in those who walked at a brisk pace less than 0.5 hours a day than in those who walked at a brisk pace 0.5 hours a day or more.
Table 3 shows the results of multiple linear regression analyses for LDL cholesterol, HDL cholesterol and Log triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol in relation to age and lifestyle factors.Independent and significant correlates with LDL cholesterol, HDL cholesterol and Log triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol were, in the order of relative importance: BMI, alcohol intake (negative) and age for LDL cholesterol level; BMI (negative), cigarette smoking (negative), alcohol intake, consideration for nutritional balance, hours of brisk walking, hours of walking at an ordinary pace and physical exercise for HDL cholesterol level; BMI, cigarette smoking, consideration for nutritional balance (negative), hours of work (negative), alcohol intake and coffee drinking (negative) for Log triglyceride level; and BMI, alcohol intake (negative), cigarette smoking, consideration for nutritional balance (negative), age, hours of brisk walking (negative) and the frequency of snack intake between meals for the ratio of LDL cholesterol to HDL cholesterol.The cumulative percentages of variation for LDL cholesterol, HDL cholesterol and Log triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol were 5.0%, 17.8%, 15.5% and 13.8%, respectively.

DISCUSSION
As expected, overall obesity indicated by BMI was found to be positively associated with LDL cholesterol and triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol and negatively associated with HDL cholesterol level, and BMI was the most important factor for atherogenicity in serum lipid profiles.Obesity has been found to be accompanied by an increased risk of CHD 24), but whether obesity is an independent risk factor for CHD is still uncertain, since CHD is mediated mainly through the metabolic consequences of obesity: increased levels of LDL cholesterol4-8) and triglyceride 5,6) and reduced levels of HDL cholesterol 6-8) as well as hypertension 25,26) and glucose intolerance and diabetes mellitus 27,28).However, the fact that weight reduction in obese patients affects these other risk factors for CHD makes obesity important in the treatment of lipid disorders 18,29.30).Although only 11.8% of our participants were deemed overweight (BMI * 26.4 kg/m2), obesity should be a major target for CHD prevention in middle-aged Japanese men.
We showed that alcohol intake was positively association with HDL cholesterol and triglyceride levels.On the other hand, alcohol intake had an inverse association with LDL cholesterol level and the ratio of LDL cholesterol to HDL cholesterol.These findings are consistent with the results of previous studies 8, 10,12,14) It can therefore be suggested that alcohol has an anti-atherogenic effect by altering both HDL and LDL cholesterol, resulting in the decreased risk in serum lipid levels.However, clinical opinion holds that abstinence from alcohol is fundamental to the control of hypertriglyceridemia.
As for the effects of alcohol intake on health, an inverse association between drinking alcohol and the mortality and incidence of CHD have been found [31][32][33][34] .Reports from the Lipid Research Clinics Follow-up Study and a Multiple Risk Factor Intervention Trial have suggested that approximately 45-50% of the association between average alcohol consumption and death from CIID may be attributable to HDL cholesterol level 35,36).Recent studies on the effect of alcohol on platelet function have revealed that platelet aggregation is significantly inhibited by alcohol, which might be another mechanism of protection from CHD in moderate drinkers 37.38).However, large amounts of alcohol intake are associated with higher risk of mortality from hypertension, stroke, cardiomyopathy and cirrhosis 32.33).Therefore, moderation in drinking should be recommended for the prevention of cardiovascular disease.
As for smoking, many studies have noted an inverse relationship between smoking and HDL cholesterol levels all) The triglyceride level in whole serum and a very low density lipoprotein (VLDL) fraction have been also found to increase with cigarette smoking 10).Phillips et al. 10) have reported a positive association between the amount of cigarettes smoked and beta lipoproteins and posited that this effect is secondary to the higher VLDL triglyceride levels in smokers.We also showed that current cigarette smoking was negatively associated with HDL cholesterol level and positively associated with triglyceride level and the ratio of LDL cholesterol to HDL cholesterol.In the population surveyed for this study, more than half of our participants smoked cigarettes, smoking cessation is one of the most effective factors in health education programs at the workplace to reduce the risk of CHD.
Favorable effects of regular physical activity on increased levels of HDL cholesterol and reduced levels of triglyceride have been observed 15-18).Nikkila et al. 15)have reported that endurance training is associated with an adaptive increase in Eating breakfast: 1 for hardly ever, 2 for sometimes, 3 for every morning .Snack intake between meals: I for hardly ever, 2 for sometimes, 3 for every day .Consideration for nutritional balance: I for hardly ever, 2 for sometimes , 3 for always.Coffee drinking (cups/day): I for hardly ever , 2 for I or 2, 3 or more.Hours of walking at ordinary speed (hours/day): I for < 0 .5, 2 for 0.5-0.9, 3 for > 1.0.Hours of brisk walking (hours/day): 1 for < 0.5, 2 for 0.5-0 .9, 3 for * 1.0.Working hours (hours/day): I for * 8.0, 2 for 8.1-9.9, 3 for * 10 .0.Physical exercise (times/week): I for hardly ever, 2 for once , 3 for twice or more.Sleeping hours (hours/night): I for * 6.5, 2 for 6.5-7.4,3 for * 7 .5.
lipoprotein lipase (LPL) activity not only in skeletal muscle but also in adipose tissue and that the high HDL cholesterol levels of physically active people are probably accounted for , at least partly, by the increase in LPL activity and the concomitant rapid turnover of triglyceride-rich lipoproteins.In this study , HDL cholesterol level was positively associated with physical exercise and the hours of walking at an ordinary pace and at a brisk pace.Furthermore, the hours of brisk walking showed a negative association with the ratio of LDL cholesterol to HDL cholesterol.
We assume that for our population walking long Variables and values of the study were as follows: Age (years): exact values.
hours, especially at a brisk pace, may be an important preventive modality for subjects with reduced levels of HDL cholesterol and increased ratios of LDL cholesterol to HDL cholesterol and may have a beneficial protective effect on CHD.
Several studies 3941) have reported that consumption of unfil-tered, boiled coffee is closely associated with raised serum cholesterol levels.The diterpenes cafestol and kahweol (nontriglyceride lipids present in coffee) are shown to be responsible for hypercholesterolemic effects of boiled coffee 42,43).On the other hand, instant or percolator coffee is reported to have

Table 1 .
Characteristics of 1561 Japanese male office workers aged 35 to 59 years.
* Data for LDL cholesterol were available for 1519 men .

Table 3 .
Multiple linear regression analyses of LDL cholesterol, HDL cholesterol and Log triglyceridelevels and the ratio of LDL cholesterol to HDL cholesterol in relation to age and lifestyle factors.

Table 3 .
(continued) Multiple linear regression analyses of LDL cholesterol, HDL cholesterol and Log triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol in relation to age and lifestyle factors.
0% and others 12.1%), and no one engaged in physical or muscular labor.Age-adjusted means of LDL cholesterol, HDL cholesterol, and Log triglyceride levels and the ratio of LDL cholesterol to HDL cholesterol were not significantly different among the four subgroups of job category, but the potential effect of the level or strength at work on serum lipids deserves further investigation.Fourth, waking speed was not measured quantitatively in the present study, and the questions used in this study may be too crude.Further investigations are needed to clarify how long we should walk a day and what speed is appropriate at walking for promoting better health.Despite these potential limitations, our findings present that obesity, current cigarette smoking and the frequency of snack intake between meals are closely associated with an increased risk of atherogenic lipid profiles.On the other hand, alcohol consumption, consideration for nutritional balance and walking long hours, especially at a brisk pace, may have an anti-atherogenic effect by altering serum lipid profiles in middle-aged Japanese men.as mediators for the effects of alcohol consumption and