Association Between Alcohol Intake and Lipids in Diabetes
Association Between Alcohol Intake and Lipids in Diabetes
A cross-sectional study was performed using a local population-based database. The subjects in the original database of the health checkup were male workers aged from 35 to 70 years (n = 37693) who had received periodic health examinations at their workplaces in Yamagata Prefecture in Japan. Subjects with diabetes (n = 1477) were extracted from the database according to the definition of diabetes given below. Subjects with diabetes were defined as those showing high hemoglobin A1C levels (≥ 6.5%), according to the recent criteria for diagnosis of diabetes by the American Diabetes Association, and/or having a current history of drug therapy for diabetes. Those receiving treatment for dyslipidemia were excluded from the subjects. All of the subjects were of Japanese origin. Subjects who were receiving treatment for any illness were requested to state the names of the diseases in a questionnaire at the health checkup. This study was approved by the Ethics Committee of Yamagata University School of Medicine. The histories of alcohol consumption, cigarette smoking and regular exercise were also surveyed by questionnaires.
The average alcohol consumption of each subject per week was reported on questionnaires during health examinations at each workplace. Since it is difficult to know the correct average alcohol consumption of occasional drinkers, only regular drinkers who drank almost every day were used as drinkers for the analysis in this study. The usual daily alcohol consumption was calculated in terms of the equivalent number of "go", a traditional Japanese unit of sake (rice wine). The amounts of other alcoholic beverages, including beer, wine, whisky and shochu (a traditional Japanese distilled spirit), were converted and expressed as units of "go". One go approximately corresponds to 180 ml of sake, 500 ml of beer, 240 ml of wine, 60 ml of whisky and 80 ml of shochu. The amount of alcohol consumed daily was categorized as "null", "less than 1 go per day", "1 go or more, but less than 2 go per day", "2 go or more, but less than 3 go per day" and "3 go or more per day". One "go" contains about 22 g of ethanol, and this amount was used to separate moderate drinkers from light drinkers since it is generally accepted that alcohol intake should be reduced to less than 20 – 30 g per day from the viewpoint of the prevention of hypertension. The average daily alcohol intake (grams of ethanol per day) was then calculated. The subjects were divided into four groups according to the ethanol consumption per day (non-drinkers; light drinkers: < 22 g of ethanol per day; moderate drinkers: ≥ 22 g and < 44 g of ethanol per day; heavy drinkers: ≥ 44 g of ethanol per day).
The height and body weight were measured with the subjects wearing light clothes at the health checkup. The waist circumference was measured at the navel level according to the recommendation of the definition of the Japanese Committee for the Diagnostic Criteria of Metabolic Syndrome. Fasted blood was sampled from each subject in the morning, and the serum triglycerides, HDL cholesterol and LDL cholesterol levels were measured by enzymatic methods using commercial kits: the pureauto S TG-N, cholestest N-HDL and cholestest LDL (Sekisui Medical Co., Ltd, Tokyo, Japan), respectively. The coefficients of variation for the reproducibility of each measurement were ≤ 3% for triglycerides, ≤ 5% for HDL cholesterol and ≤ 5% for LDL cholesterol. The cut-off values for a high LDL-C/HDL-C ratio and high TG/HDL-C ratio were defined as 3.5 and 3.75, respectively. The LAP was determined by using the triglycerides (TG) level and waist circumference (WC) as follows: LAP = TG (mmol/L) × (WC (cm) – 65). The values of LAP were arranged in ascending order, and the subjects were then divided into three groups of approximately equal sizes. Subjects in the highest tertile of LAP were defined as subjects with a high LAP, since a common cut-off value for LAP has not been confirmed. Hemoglobin A1c was measured by the NGSP (National Glycohemoglobin Standardization Program)-approved technique using the latex cohesion method with a commercial kit (Determiner HbA1c, Kyowa Medex, Tokyo, Japan). The coefficient of variation for reproducibility of the hemoglobin A1c measurement was ≤ 5%. Since the standards of hemoglobin A1c used for measurement are different in the NGSP method and JDS (the Japan Diabetes Society) method, the hemoglobin A1c values were calibrated by using a formula proposed by the JDS: hemoglobin A1c (NGSP) (%) = 1.02 × hemoglobin A1c (JDS) (%) + 0.25%.
The statistical analyses were performed using a computer software program (SPSS version 16.0 J for Windows, Chicago IL, USA). The percentages of smokers, subjects exercising regularly and subjects receiving drug therapy for diabetes were compared between each pair of groups using the chi-square test for independence. In the univariate analysis, means of each variable were compared among the groups by using an analysis of variance (ANOVA) followed by Scheffé's F-test as a post-hoc test. In the multivariate analysis, the mean levels of each variable were compared by using an analysis of covariance (ANCOVA), followed by Student's t-test after Bonferroni correction. Since the triglycerides, TG/HDL-C ratio and LAP levels did not show a normal distribution, these parameters were compared between the groups non-parametrically by using the Kruskal-Wallis test, followed by the Steel-Dwass test as a post-hoc test in the univariate analysis (ANOVA), or were used after log-transformation in the multivariate analysis (ANCOVA). In the logistic regression analysis, the crude and adjusted odds ratios for a high LDL-C/HDL-C ratio, high TG/HDL-C ratio, high LAP or a combination of these high lipid indices were calculated. Age, smoking, regular exercise and drug therapy for diabetes were used as other explanatory variables or covariables in the multivariate analyses. In the analyses of variables other than waist circumference and LAP, body weight was also added to the explanatory variables and covariables. Probability (p) values less than 0.05 were defined as significant.
Methods
Subjects
A cross-sectional study was performed using a local population-based database. The subjects in the original database of the health checkup were male workers aged from 35 to 70 years (n = 37693) who had received periodic health examinations at their workplaces in Yamagata Prefecture in Japan. Subjects with diabetes (n = 1477) were extracted from the database according to the definition of diabetes given below. Subjects with diabetes were defined as those showing high hemoglobin A1C levels (≥ 6.5%), according to the recent criteria for diagnosis of diabetes by the American Diabetes Association, and/or having a current history of drug therapy for diabetes. Those receiving treatment for dyslipidemia were excluded from the subjects. All of the subjects were of Japanese origin. Subjects who were receiving treatment for any illness were requested to state the names of the diseases in a questionnaire at the health checkup. This study was approved by the Ethics Committee of Yamagata University School of Medicine. The histories of alcohol consumption, cigarette smoking and regular exercise were also surveyed by questionnaires.
Classification of Drinker Groups
The average alcohol consumption of each subject per week was reported on questionnaires during health examinations at each workplace. Since it is difficult to know the correct average alcohol consumption of occasional drinkers, only regular drinkers who drank almost every day were used as drinkers for the analysis in this study. The usual daily alcohol consumption was calculated in terms of the equivalent number of "go", a traditional Japanese unit of sake (rice wine). The amounts of other alcoholic beverages, including beer, wine, whisky and shochu (a traditional Japanese distilled spirit), were converted and expressed as units of "go". One go approximately corresponds to 180 ml of sake, 500 ml of beer, 240 ml of wine, 60 ml of whisky and 80 ml of shochu. The amount of alcohol consumed daily was categorized as "null", "less than 1 go per day", "1 go or more, but less than 2 go per day", "2 go or more, but less than 3 go per day" and "3 go or more per day". One "go" contains about 22 g of ethanol, and this amount was used to separate moderate drinkers from light drinkers since it is generally accepted that alcohol intake should be reduced to less than 20 – 30 g per day from the viewpoint of the prevention of hypertension. The average daily alcohol intake (grams of ethanol per day) was then calculated. The subjects were divided into four groups according to the ethanol consumption per day (non-drinkers; light drinkers: < 22 g of ethanol per day; moderate drinkers: ≥ 22 g and < 44 g of ethanol per day; heavy drinkers: ≥ 44 g of ethanol per day).
Measurements
The height and body weight were measured with the subjects wearing light clothes at the health checkup. The waist circumference was measured at the navel level according to the recommendation of the definition of the Japanese Committee for the Diagnostic Criteria of Metabolic Syndrome. Fasted blood was sampled from each subject in the morning, and the serum triglycerides, HDL cholesterol and LDL cholesterol levels were measured by enzymatic methods using commercial kits: the pureauto S TG-N, cholestest N-HDL and cholestest LDL (Sekisui Medical Co., Ltd, Tokyo, Japan), respectively. The coefficients of variation for the reproducibility of each measurement were ≤ 3% for triglycerides, ≤ 5% for HDL cholesterol and ≤ 5% for LDL cholesterol. The cut-off values for a high LDL-C/HDL-C ratio and high TG/HDL-C ratio were defined as 3.5 and 3.75, respectively. The LAP was determined by using the triglycerides (TG) level and waist circumference (WC) as follows: LAP = TG (mmol/L) × (WC (cm) – 65). The values of LAP were arranged in ascending order, and the subjects were then divided into three groups of approximately equal sizes. Subjects in the highest tertile of LAP were defined as subjects with a high LAP, since a common cut-off value for LAP has not been confirmed. Hemoglobin A1c was measured by the NGSP (National Glycohemoglobin Standardization Program)-approved technique using the latex cohesion method with a commercial kit (Determiner HbA1c, Kyowa Medex, Tokyo, Japan). The coefficient of variation for reproducibility of the hemoglobin A1c measurement was ≤ 5%. Since the standards of hemoglobin A1c used for measurement are different in the NGSP method and JDS (the Japan Diabetes Society) method, the hemoglobin A1c values were calibrated by using a formula proposed by the JDS: hemoglobin A1c (NGSP) (%) = 1.02 × hemoglobin A1c (JDS) (%) + 0.25%.
Statistical Analysis
The statistical analyses were performed using a computer software program (SPSS version 16.0 J for Windows, Chicago IL, USA). The percentages of smokers, subjects exercising regularly and subjects receiving drug therapy for diabetes were compared between each pair of groups using the chi-square test for independence. In the univariate analysis, means of each variable were compared among the groups by using an analysis of variance (ANOVA) followed by Scheffé's F-test as a post-hoc test. In the multivariate analysis, the mean levels of each variable were compared by using an analysis of covariance (ANCOVA), followed by Student's t-test after Bonferroni correction. Since the triglycerides, TG/HDL-C ratio and LAP levels did not show a normal distribution, these parameters were compared between the groups non-parametrically by using the Kruskal-Wallis test, followed by the Steel-Dwass test as a post-hoc test in the univariate analysis (ANOVA), or were used after log-transformation in the multivariate analysis (ANCOVA). In the logistic regression analysis, the crude and adjusted odds ratios for a high LDL-C/HDL-C ratio, high TG/HDL-C ratio, high LAP or a combination of these high lipid indices were calculated. Age, smoking, regular exercise and drug therapy for diabetes were used as other explanatory variables or covariables in the multivariate analyses. In the analyses of variables other than waist circumference and LAP, body weight was also added to the explanatory variables and covariables. Probability (p) values less than 0.05 were defined as significant.
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