Modification of the association of alcohol drinking with blood pressure by cigarette smoking

Abstract

The purpose of this study was to investigate whether the association of alcohol drinking with blood pressure was modified by cigarette smoking. The subjects were healthy male workers aged 40–59 years and were divided into three different groups by average daily consumption of alcohol (non‐drinkers; light drinkers, less than 30 g ethanol per day; heavy drinkers, 30 g or more ethanol per day) and cigarettes (non‐smokers; light smokers, less than 20 cigarettes per day; heavy smokers, 20 cigarettes or more per day). The mean levels of both systolic and diastolic blood pressures were significantly lower in the light and heavy smoker groups than in the non‐smoker group. In the light and heavy smoker groups, systolic blood pressure was higher in the light drinker subgroup than in the non‐drinker subgroup, while there was no significant difference between systolic blood pressures in the non‐ and light drinker subgroups of non‐smokers. In the non‐, light and heavy smoker groups, systolic and diastolic blood pressures were significantly higher in the heavy drinker subgroup than in the non‐drinker subgroup, and these differences tended to be greater in light and heavy smokers than in non‐smokers. The above differences in the relationships of alcohol drinking with blood pressure in non‐, light and heavy smokers were also observed when age and body mass index were adjusted and when alcohol intake‐matched groups were used. These results suggest that the association of alcohol drinking with blood pressure is stronger in smokers than in non‐smokers, independently of age, body mass index and alcohol intake.

• alcohol drinking
• atherosclerosis
• blood pressure
• cigarette smoking
• hypertension

Introduction

Habitual alcohol drinking contributes to induction of hypertension [1], [2]. Alcohol has been estimated to contribute to 16% of all hypertensive diseases [3]. A meta‐analysis study has shown that alcohol reduction was associated with significant reductions in mean systolic and diastolic blood pressures of −3.31 mmHg and −2.04 mmHg, respectively [4]. Although adrenergic discharge associated with withdrawal of alcohol intake has been suggested as an important mechanism, the exact mechanism for alcohol‐induced hypertension still remains to be clarified [5].

Cigarette smoking is a major risk factor for atherosclerotic disease [6], [7]. A variety of mechanisms, including injury of the vascular endothelium and lipid peroxidation, have been proposed for the mechanisms of facilitation of atherosclerotic progression by smoking [8], [9]. Blood pressure has been shown to be lower in smokers than in non‐smokers [10–13], whereas there have also been studies showing no significant difference between blood pressures in smokers and non‐smokers [14], [15]. There is a strong association between smoking and drinking habits [16]. However, there has been very limited information on the effect of drinking–smoking interaction on blood pressure. The association of alcohol drinking with blood pressure has been reported to be stronger in smokers than in non‐smokers in German, Dutch and English subjects [17–19]. However, it has not been determined whether there is a dose–response effect of smoking on the association of alcohol drinking with blood pressure. Moreover, there have been no studies on the effects of smoking on alcohol–blood pressure relationships with difference in alcohol consumption between smokers and non‐smokers being taken into account. Higher alcohol intake in smokers than in non‐smokers is thought to considerably influence the relationship between alcohol drinking and blood pressure.

The purpose of this concise study was therefore to investigate whether the association of alcohol drinking with blood pressure was different in smokers and non‐smokers using Japanese subjects with different degrees of cigarette consumption and using alcohol intake‐matched groups of smokers and non‐smokers.

Methods

Subjects

The subjects of this cross‐sectional study were 27 845 healthy men, aged from 40 to 59 years, who underwent periodic health examinations at their workplaces. In Japan, workers in companies with 50 employees or more must undergo annual health checkups, and the companies are required by law to pay the costs for health checkups of the workers. The annual health checkup included a clinical examination, blood screening (GOT, GPT, γGTP, total cholesterol, triglyceride, HDL cholesterol, glucose, hemoglobin and red blood cell), urine screening (glucose and protein) and electrocardiogram. The subjects were consecutively enrolled by a major health‐checkup company in the Yamagata Prefecture of Japan. Data from a database on periodic medical check‐ups, which was prepared by the health‐checkup company, were used in this study, and the data for each subject were registered in the database only by code numbers. Workers from various kinds of companies (e.g. construction, manufacturing, information and communications, transport, wholesale and retail trade, eating and drinking places, accommodations, and services) were included in the subjects. The present study protocol was approved by the Ethics Committee of Yamagata University School of Medicine. Subjects who indicated in the questionnaire that they had a present illness were excluded from the subjects of this study. The major illnesses for exclusion were hypertension (8.26%), peptic ulcer (3.77%), diabetes mellitus (2.61%), low back pain (1.39%), dyslipidemia (1.31%), liver disease (1.03%), hyperuricemia (0.97%), arrhythmia (0.70%), ischemic heart disease (0.65%) and stroke (0.41%).

Measurements

Blood pressure in a sitting position was measured only once by trained nurses with a mercury sphygmomanometer after each subject had rested quietly for at least 5 min. Korotkoff phase V was used to define diastolic pressure. Body mass index (BMI) was calculated as weight in kilograms divided by the square of height in meters.

Classification of alcohol drinkers and smokers

Average alcohol consumption of each subject per week and average cigarette consumption per day were reported on questionnaires during the health examinations at each workplace. Usual weekly alcohol consumption was recorded in terms of the equivalent number of “go”, a traditional Japanese unit of amount of sake (rice wine). One “go” contains about 28 ml of ethanol. The amounts of other alcoholic beverages, including beer, wine and whisky, were converted and expressed as units of “go”. Average daily alcohol intake (grams of ethanol per day) was then calculated. The subjects in each age group were divided into three groups according to ethanol consumption per day (non‐drinkers; light drinkers, less than 30 g per day; heavy drinkers, 30 g or more per day). The value of 30 g per day was used to separate heavy drinkers from light drinkers because it is recommended for prevention of hypertension to reduce ethanol consumption to less than 20–30 g per day for men [20]. One pack of cigarette generally contains 20 cigarettes, a number that is often used for dividing light and heavy smokers in surveys. The subjects were divided into three groups by average cigarette consumption (non‐smokers; light smokers, less than 20 cigarettes per day; heavy smokers, 20 or more cigarettes per day).

Since alcohol consumption was different in smokers and non‐smokers (Table I), alcohol intake‐matched groups of non‐, light and heavy smokers were also used in a part of the analysis in order to compare the relationships of alcohol drinking with blood pressure among the smoking groups. Alcohol intake‐matched groups were prepared as follows. Subjects were selected from each alcohol intake category randomly and the subject number of each alcohol intake category was adjusted to be the same among the non‐smoker, light smoker and heavy smoker groups

Table I. Profiles of overall subjects and alcohol intake‐matched subjects.

	Overall	Alcohol intake‐matched
Subject number
Non‐smokers
Total	9801	7164
Non‐drinkers	2454	1797
Light drinkers	4182	2295
Heavy drinkers	3165	3072
Light smokers
Total	9816	7164
Non‐drinkers	2192	1797
Light drinkers	3617	2295
Heavy drinkers	4007	3072
Heavy smokers
Total	8228	7164
Non‐drinkers	1797	1797
Light drinkers	2295	2295
Heavy drinkers	4136	3072
Age (years)
Non‐smokers	48.9±5.3	49.0±5.3
Light smokers	48.1±5.5**	48.2±5.5**
Heavy smokers	47.4±5.0**,††	47.4±5.0**,††
BMI (kg/m^2)
Non‐smokers	23.93±2.84	23.95±2.83
Light smokers	22.88±2.88**	22.88±2.93**
Heavy smokers	23.35±2.96**,††	23.37±2.97**,††
SBP (mmHg)
Non‐smokers	130.1±15.9	130.6±16.1
Light smokers	128.8±16.4**	128.6±16.2**
Heavy smokers	128.8±16.3**	128.3±16.2**
DBP (mmHg)
Non‐smokers	79.0±10.9	79.4±10.9
Light smokers	77.2±10.8**	77.1±10.7**
Heavy smokers	77.7±11.0**,†	77.3±11.0**
Alcohol intake (g/day)
Non‐smokers	27.1±28.1	31.8±29.8
Light smokers	31.8±30.1**	31.8±29.8
Heavy smokers	38.1±33.9**,††	31.8±29.8

Numbers of subjects and means with standard deviations of each variable are shown. Light smokers, less than 20 cigarettes per day; heavy smokers, 20 or more cigarettes per day. Light drinkers, less than 30 g of ethanol per day; heavy drinkers, 30 g or more of ethanol per day. BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure. p<0.01 (**) compared with non‐drinkers; p<0.05 (†) and p<0.01 (††) compared with light drinkers.

Statistical analysis

Statistical analyses were performed using computer software (SPSS version 14.0J for Windows). Comparison of each variable among the three groups of cigarette smoking or alcohol drinking was performed by using analysis of variance (ANOVA) followed by Scheffé's F‐test. In multivariate analysis, each variable was calculated after adjustment for age and BMI, and the mean levels were compared between the groups using ANOVA and then Student's t‐test after Bonferroni correction. Probability (p) values less than 0.05 were defined as significant.

Results

Profile of subjects

Profiles of subjects divided into groups by habitual smoking are shown in Table I. When overall subjects were used, mean age was significantly younger in the light and heavy smoker groups than in the non‐smoker group and was significantly younger in the heavy smoker group than in the light smoker group. The mean BMI was significantly lower in the light and heavy smoker groups than in the non‐smoker group and significantly lower in the light smoker group than in the heavy smoker group. Both the mean levels of systolic and diastolic blood pressures were significantly lower in the light and heavy smoker groups than in the non‐smoker group. The mean daily alcohol intake was significantly higher in the light and heavy smoker groups than in the non‐smoker group and was significantly higher in the heavy smoker group than in the light smoker group. The above relationships of smoking with age, BMI and systolic and diastolic blood pressures were also observed when alcohol intake‐matched groups were used (Table I).

Univariate analysis of relationships of alcohol drinking with systolic blood pressure in smokers and non‐smokers

Blood pressure was compared among non‐, light and heavy drinker subgroups in each group of cigarette consumption (Figure 1A). Systolic blood pressure was significantly higher in light drinkers than in non‐drinkers in the light and heavy smoker groups but was not significantly different in non‐drinkers and light drinkers of the non‐smoker group. In the non‐, light and heavy smoker groups, systolic blood pressure was significantly higher in the heavy drinker subgroup than in the non‐drinker and light drinker subgroups. The difference between levels of systolic blood pressure in non‐drinkers and heavy drinkers tended to be greater in the light and heavy smoker groups than in the non‐smoker group.

Figure 1 Univariate analysis, using overall subjects(A) and alcohol intake‐matched subjects (B), of the relationships between blood pressure and alcohol drinking in different groups divided by daily cigarette consumption. Means with standard errors are shown. Light smokers, less than 20 cigarettes per day; heavy smokers, 20 or more cigarettes per day. Light drinkers, less than 30 g of ethanol per day; heavy drinkers, 30 g or more of ethanol per day. p<0.01 (**) compared with non‐drinkers; p<0.01 (††) compared with light drinkers.

Univariate analysis of relationships of alcohol drinking with diastolic blood pressure in smokers and non‐smokers

In the non‐, light and heavy smoker groups, diastolic blood pressure was significantly higher in light drinkers than in non‐drinkers and was significantly higher in heavy drinkers than in non‐drinkers and light drinkers (Figure 1A). The difference between levels of diastolic blood pressure in the non‐ and heavy drinker subgroups also tended to be greater in the light and heavy smoker groups than in the non‐smoker group.

Multivariate analysis of relationships of alcohol drinking with systolic and diastolic blood pressure after adjustment for alcohol intake, age and BMI

The aforementioned relationships of alcohol drinking with systolic and diastolic blood pressure in non‐, light and heavy smokers were also observed when alcohol intake‐matched subject groups were used (Figure 1B, Table II) and when age and BMI were adjusted in the multivariate study (Table II).

Table II. Multivariate analysis, using overall subjects and alcohol intake‐matched subjects, of the relationships between blood pressure and alcohol drinking in different groups divided by daily cigarette consumption.

	Non‐smokers	Light smokers	Heavy smokers
Overall
SBP (mmHg)
Non‐drinkers	128.1±0.3	124.9±0.3	124.3±0.4
Light drinkers	128.8±0.2	127.5±0.3**	126.5±0.3**
Heavy drinkers	133.4±0.3**,††	132.1±0.2**,††	132.0±0.2**,††
DBP (mmHg)
Non‐drinkers	77.3±0.2	74.5±0.2	74.4±0.2
Light drinkers	78.5±0.2**	76.6±0.2**	76.3±0.2**
Heavy drinkers	81.0±0.2**,††	79.3±0.2**,††	79.9±0.2**,††
Alcohol intake‐matched
SBP (mmHg)
Non‐drinkers	128.2±0.4	124.9±0.4	124.3±0.4
Light drinkers	128.8±0.3	127.2±0.3**	126.5±0.3**
Heavy drinkers	133.5±0.3**,††	131.7±0.3**,††	131.9±0.3**,††
DBP (mmHg)
Non‐drinkers	77.3±0.2	74.5±0.2	74.5±0.2
Light drinkers	78.8±0.2**	76.3±0.2**	76.3±0.2**
Heavy drinkers	81.0±0.2**,††	79.2±0.2**,††	79.8±0.2**,††

Means with standard errors after adjusting age and body mass index are shown. Light smokers, less than 20 cigarettes per day; heavy smokers, 20 or more cigarettes per day. Light drinkers, less than 30 g of ethanol per day; heavy drinkers, 30 g or more of ethanol per day. SBP, systolic blood pressure; DBP, diastolic blood pressure. p<0.01 (**) compared with non‐drinkers; p<0.01 (††) compared with light drinkers.

Blood pressure in finer‐classified groups of alcohol drinking and cigarette smoking

The relationships between alcohol drinking and blood pressure in each smoking group were also investigated using finer‐classified groups of alcohol drinking (super‐light drinkers, less than 15 g ethanol/day; light drinkers, 15 g or more and less than 30 g ethanol/day; heavy drinkers, 30 g or more and less than 60 g ethanol/day; super‐heavy drinkers, 60 g or more ethanol/day) and finer‐classified groups of smoking (light smokers, less than 20 cigarettes/day; heavy smokers, 20 or more and less than 40 cigarettes/day; super‐heavy smokers, 40 or more cigarettes/day). As shown in Table III, systolic and diastolic blood pressure after adjustment for age and BMI increased in light, heavy and super‐heavy drinkers, depending on alcohol intake, and the increases in systolic and diastolic blood pressure in drinkers tended to be greater in smokers as cigarette consumption increases. No statistical differences in systolic and diastolic blood pressure between the light drinker and non‐drinker subgroups in the super‐heavy smokers may be due to the small number of subjects in the super‐heavy smoker group.

Table III. Multivariate analysis, using overall subjects divided into five drinking groups and four smoking groups, of the relationships between blood pressure and alcohol drinking in different groups divided by daily cigarette consumption.

Overall	Non‐smokers	Light smokers	Heavy smokers	Super‐heavy smokers
SBP (mmHg)
Non‐drinkers	128.1±0.3	124.9±0.3	124.4±0.4	123.1±1.2
Super‐light drinkers	127.4±0.4	125.9±0.5	125.3±0.7	122.6±2.2
Light drinkers	129.4±0.3*	128.2±0.3**	127.1±0.4**	125.9±1.5
Heavy drinkers	132.8±0.3**	131.8±0.3**	131.3±0.3**	130.6±1.3**
Super‐heavy drinkers	135.1±0.5**	133.0±0.5**	133.3±0.4**	134.7±1.2**
DBP (mmHg)	77.3±0.2	74.5±0.2	74.4±0.3	74.8±0.8
Non‐drinkers
Super‐light drinkers	77.5±0.3	75.6±0.3*	75.2±0.4	74.0±1.4
Light drinkers	79.0±0.2**	77.0±0.2**	76.6±0.3**	76.8±1.0
Heavy drinkers	80.8±0.2**	79.1±0.2**	79.3±0.2**	80.2±0.8**
Super‐heavy drinkers	81.5±0.4**	80.0±0.3**	80.7±0.3**	81.8±0.8**

Means with standard errors after adjusting age and body mass index are shown. Light smokers, less than 20 cigarettes per day; heavy smokers, 20 or more and less than 40 cigarettes per day; super‐heavy smokers, 40 or more cigarettes per day. Super‐light drinkers, less than 15 g of ethanol per day; light drinkers, 15 g or more and less than 30 g of ethanol per day; heavy drinkers, 30 g or more and less than 60 g of ethanol per day; super‐heavy drinkers, 60 g or more of ethanol per day. SBP, systolic blood pressure; DBP, diastolic blood pressure. The numbers of subjects in each group are 2454 (non‐smokers and non‐drinkers), 1336 (non‐smokers and super‐light drinkers), 2846 (non‐smokers and light drinkers), 2413 (non‐smokers and heavy drinkers), 752 (non‐smokers and super‐heavy drinkers), 2192 (light smokers and non‐drinkers), 1021 (light smokers and super‐light drinkers), 2596 (light smokers and light drinkers), 2960 (light smokers and heavy drinkers), 1047 (light smokers and super‐heavy drinkers), 1651 (heavy smokers and non‐drinkers), 538 (heavy smokers and super‐light drinkers), 1613 (heavy smokers and light drinkers), 2547 (heavy smokers and heavy drinkers), 1287 (heavy smokers and super‐heavy drinkers), 146 (super‐heavy smokers and non‐drinkers), 47 (super‐heavy smokers and super‐light drinkers), 97 (super‐heavy smokers and light drinkers), 139 (super‐heavy smokers and heavy drinkers and 163 (super‐heavy smokers and super‐heavy drinkers). p<0.05 (*) and p<0.01 (**) compared with non‐drinkers.

Discussion

A significantly higher systolic blood pressure in light drinkers than in non‐drinkers was observed in smokers but not in non‐smokers, and increases in mean levels of both systolic and diastolic blood pressures in heavy drinkers compared with those in non‐drinkers tended to be greater in light and heavy smokers than in non‐smokers. The above finding that the association of alcohol drinking with blood pressure is stronger in smokers than in non‐smokers was also observed when drinkers and smokers were divided into more groups. Thus, the drinking‐blood pressure association is suggested to be stronger in smokers than in non‐smokers.

It is known that there is a strong relationship between alcohol consumption and smoking [16], and, in fact, alcohol intake was significantly higher in light and heavy smokers than in non‐smokers and was significantly higher in heavy smokers than in light smokers in this study (Table I). Therefore, one possible explanation for the stronger alcohol–blood pressure association in smokers than in non‐smokers is higher alcohol consumption in smokers. However, the influence of smoking on the alcohol–blood pressure association was not changed in the analysis using the three alcohol intake‐matched groups of non‐, light and heavy smokers. Thus, the present study is the first study to show by using alcohol intake‐matched groups of smokers and non‐smokers that the influence of smoking on the alcohol–blood pressure association was independent of alcohol consumption as well as of age and BMI, which were also different between smokers and non‐smokers and between light and heavy smokers. However, the reason for the stronger alcohol–blood pressure association in smokers than in non‐smokers remains unknown.

On the other hand, increases in systolic and diastolic blood pressures in alcohol drinkers were not different in light and heavy smokers. Thus, the modifying effect of smoking on the association of alcohol drinking with blood pressure was suggested to be comparable in light and heavy smokers. The reason for this no clear dose–response relationship between smoking and its effect on the alcohol–blood pressure association is also unknown. Interestingly, a dose–response relationship was also not obtained in the relationship between smoking and blood pressure: systolic and diastolic blood pressure was lower in light and heavy smokers than in non‐smokers, while blood pressure was not lower in heavy smokers than in light smokers. This agrees with the results of previous studies on the smoking–blood pressure relationship [13], [21], [22] and suggests that neither the smoking effect on blood pressure nor the smoking effect on the association between alcohol drinking and blood pressure results from the direct effects of smoking, e.g. actions of nicotine. Although possible explanations for the difference in blood pressure between smokers and non‐smokers, such as reduction of body weight and rebound against the acute blood pressure‐elevating effect, have been proposed, the exact reason for the above difference remains unknown [23]. In the present study, the association of smoking with the alcohol–blood pressure relationship was not confounded by BMI. Further studies are needed to elucidate the chronic effects of habitual smoking on function of the cardiovascular system.

While smoking as well as hypertension is a major risk factor for atherosclerotic disease [6], [7], alcohol drinking has both beneficial and harmful effects on the progression of atherosclerosis, which are in part explained by actions of alcohol on blood lipid profiles [24], [25] and on blood pressure [26], [27], respectively. The present findings suggest that even light smoking augments the blood pressure‐elevating action of alcohol. Thus, in addition to the known atherogenic action of smoking per se, blood pressure‐elevating action of alcohol drinking is greater in smokers than in non‐smokers. Therefore, it is recommended more strongly for smokers than for non‐smokers to reduce alcohol intake from the viewpoint of prevention of hypertension, although blood pressure is slightly but significantly lower in smokers than in non‐smokers.

There is a possible bias for this study as follows. Several possible confounders for the relationship between alcohol drinking and blood pressure, such as diet, nutrition, physical activity and genetic sensitivity to alcohol, were not investigated in the present study. Since this study is a cross‐sectional study, causal relationships among blood pressure, alcohol drinking and smoking could not be concluded. Therefore, further prospective studies including the above explanatory factors are needed in the future to clarify the effect of smoking on the association of alcohol drinking with blood pressure.

In conclusion, the association of alcohol drinking with blood pressure is stronger in smokers than in non‐smokers, independently of age, BMI and alcohol intake.

Acknowledgements

This work was supported by a grant for scientific research from the Ministry of Education, Science and Culture of Japan (No. 19590656).