a Laboratorio di Epidemiologia e Biostatistica, Istituto Superiore di Sanità, Roma, Italy.
b Dipartimento di Medicina Interna e Scienze Endocrine e Metaboliche, Università di Perugia, Italy.
c Associazione per la Ricerca cardiologica, Roma, Italy.
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Abstract |
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Methods In 1965, a total of 1536 Italian males aged 4565 years underwent an examination which included: a general questionnaire, anthropometric measurements, an overall physical examination, ECG recording, blood pressure and serum cholesterol measurements and measurement of food consumption including alcohol. The cohort was followed for total mortality from 1965 to 1995.
Results During a period of 30 years 1096 deaths occurred. Age-adjusted life expectancy for men assuming a mean daily quantity of 63 g of alcohol (range 47 drinks per day) was 21.6 ± 0.4 years, roughly 2 years more than men taking a mean quantity of 3.7 g (1 drink) and men consuming >10 drinks per day. Taking smoking habit into account, the longest survival of 22.4 ± 0.5 years was observed in non-smokers drinking 47 drinks daily; the lowest, 18.5 ± 0.7 years, in smokers drinking >10 drinks. Stratifying for physical activity, the longest survival (23.4 ± 0.7 years) was experienced by men engaged in heavy physical activity at work drinking 14 drinks per day.
Conclusions The relationship between life expectancy and alcohol consumption (97% wine in this Italian cohort and mostly red wine) is confirmed to be non-linear. Men aged 4564 at entry drinking about 5 drinks per day have a longer life expectancy than occasional and heavy drinkers.
Keywords Alcohol, survival, cohort study, men, Italy
Accepted 17 December 1999
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Introduction |
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In a 1992 paper by some of the authors of this study, concerning a 20-year follow-up of an Italian rural cohort of men, aged 4565 years at the entry examination in 1965, a U-shaped relation between alcohol consumption and mortality was shown.4 In the present study, which applies to a 30-year follow-up of the same cohort, we examine the relation between survival and alcohol consumption, controlling for smoking habit and physical activity, and comparing groups in terms of life expectancy rather than in terms of mortality rates (30-year crude mortality rates are unlikely to differ much for different subgroups since in a few years the whole group will be deceased and the crude mortality rate will be 100% in each group).
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Subjects and Methods |
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At baseline, 1712 men were examined, representing 98.8% of the eligible defined population (99% in MTG and 98.5% in CRV). Dietary data were then collected only in subsamples of the cohorts.
During the first 5 years of follow-up, 89 men died. The 1623 surviving participants were invited to another examination which included an individual dietary habits survey. In 1965, 1564 subjects accepted the invitation and were examined. Owing to missing data 28 people could not be considered for this analysis. Therefore, the current analysis included 1536 men aged 4564 years, representing 94.6% of those people alive in 1965 (95.6% in MTG and 93.9% in CRV).
Baseline examination
In 1965, experienced dieticians collected data on food consumption, using the dietary history method; details on the method have been provided in previous papers.17,18 Alcohol consumption was measured in glasses of wine or spirits. Beer was very seldom consumed by these rural Italian populations. Specifically, different types of glasses were shown to the subjects, and they were asked about the number and the type of glasses of wine and spirits usually consumed. For heavy drinkers, reported consumption was verified in local wine shops and among relatives. No important differences in alcohol consumption between the two villages were found. The mean consumption value was 84 g/day in MTG and 88 g/day in CRV. Since participation rates and alcohol consumption were similar in both villages, we decided to combine the two populations. Overall 97% of the alcohol was derived from wine.
In addition to the dietary survey, all subjects underwent an examination which included a general questionnaire concerning lifestyle habits and some anthropometric measurements: blood pressure and total serum cholesterol (but not [high density lipoprotein] HDL cholesterol) measurements; an ECG recording; the administration of a standard medical questionnaire mainly concerned with cardiovascular diseases; an overall physical examination. No data were collected on socioeconomic status of the subjects (only their job was known, and no data about income or education), and psychosocial factors. It should be noted that health status has been carefully assessed only for cardiovascular diseases, not for any other condition. Only age at entry, smoking habit and physical activity have been considered in the present analysis. Usual physical activity has been classified as follows: sedentary subjects engaged in little physical exercise (group 1), subjects moderately active during a substantial part of the day (group 2) and subjects performing hard physical work during most of working time (group 3).
Mortality follow-up
The mortality follow-up consisted of a complex information-gathering system which started from the official death certificate and included the collection of information from hospital physicians, relatives of the dead and other witnesses. The cause of death was assigned by a single reviewer following pre-determined criteria.15 Two subjects were lost to follow-up.
Statistical methods
Since there were only 38 non-drinkers (2.5%) among the 1536 subjects, they alone could not be taken as the reference category and had to be included in the category of occasional drinkers consuming 1 drink per day (012 g/day of alcohol). Other cutpoints were chosen at 48, 84 and 120 g/day corresponding roughly to 4, 7 and 10 glasses per day.
The survival experience of each group, after entry in the study, was described following the method suggested by Chiang.19 A life table for a follow-up population was constructed and the observed, crude and age-adjusted expectation of life was calculated.
Survival of each group was evaluated according to alcohol consumption adjusting for age and stratifying for smoking habit (yes/no) or usual physical activity (three groups).
To confirm the results obtained in the stratified analysis, the proportional hazards model was also used, adjusting at the same time for age, smoking habit and physical activity.
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Results |
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Survival rates and life expectancies
Figure 1 shows the unadjusted survival rates in some classes of alcohol consumption. The highest rate, during the whole 30-year follow-up period, was observed for men drinking 4984 g/day. Occasional (<12 g/day) and heavy drinkers (>120 g/day) showed lower survival rates. The greatest differences in survival rates are observed between 10 and 15 years after the entry examination; for longer periods, the differences decrease as would be expected since eventually all the men will die.
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Table 5 shows the estimated coefficients, and relative P-levels of three models with age and alcohol (model 1), age, alcohol and smoking habit (model 2), age, alcohol, smoking habit and physical activity (model 3). The coefficients of age, smoking habit and physical activity are always significantly different from zero. The linear coefficient of alcohol is always negative but not different from zero. The coefficient of the quadratic term of alcohol is always positive and significantly different from zero suggesting a non-linear and U-shaped relationship independent of the confounders included in each model. In fact the inclusion of new variables does not change the strength and the shape of the relationship among the main variables already considered in the model, as can be seen from the values of the coefficients of age and alcohol.
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Discussion |
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This work describes the experience of middle-aged men followed for 30 years and reports this experience in terms of life expectancy instead of relative risk. To this extent we can contribute to answering the question Do moderate drinkers live more than abstainers and heavy drinkers? And if so, what is the gain? The answer is that, in our cohort of middle-aged men, drinkers of about 60 g of alcohol per day live about 2 years more than occasional and heavy drinkers.
The amount of alcohol intake in the heavy drinker category would be regarded in many countries as binge drinking and is probably considered excessive by current standards. However, it must be considered that in this study it was derived almost exclusively from wine (97%) consumed mostly during meals, following a typical Italian pattern. Moreover, most men included in the study were engaged in heavy physical activity at work.15 Between 1970 and 1995 the consumption of wine in Italy decreased about 50% and the consumption of total alcohol by about 40%.21 In this cohort, between 1965 and 1991, the percentage of energy from beverages decreased more than 30%.18 A similar reduction has been observed in a French study recently published.6
Concerning individual habits, on the other hand, a certain stability in individual drinking patterns, in the context of an overall reduction of wine consumption, is very likely to have occurred in this cohort, although detailed data for such an analysis were not available. Such a phenomenon was observed in a recent study,9 where a second recording of alcohol consumption repeated 10 years after the first showed 95% of the non-drinkers remained abstainers or drunk occasionally and 78% of the drinkers were classified in the same or an adjacent (usually lower) consumption category.
In this study subjects with prevalent disease at entry examination were not excluded, since mortality from all causes was the considered endpoint, and complete prevalence data for all pathologies, excluding those related to cardiovascular diseases, were not assessed. In a previous work by some of the same authors the effect of not including in the analysis the subjects that develop cardiovascular pathologies in the first 5 years of the follow-up was analysed.4
Differences in life expectancies between alcohol drinkers can be compared with differences between smokers and non-smokers and with differences among men engaged in different physical activity levels. Our results show that about 2 years of life are gained by moderate drinkers both in comparison with occasional and heavy drinkers, but the same period of time is lost by smokers compared to non-smokers. This finding is not in complete agreement with another report where the benefit from moderate alcohol consumption was far smaller than the large increase in risk produced by tobacco.9
Larger differences are related to physical activity where, in comparison with sedentary men whose life expectancy is 17.5 years, men engaged in moderate activity gain 2.8 years and those engaged in heavy activity gain 3.9 years. Of course this result might also due to the well-known healthy worker effect but it must be noted that only 8% of these middle-aged men were unemployed or retired. According to our data the longest life expectancy moves toward lower values of alcohol consumption as physical activity increases. An increase in HDL cholesterol in blood induced by alcohol consumption is among the mechanisms that can possibly explain the protective effect of moderate quantities of alcohol consumption on cardiovascular and cerebrovascular diseases.6,22 It is also known that higher HDL cholesterol levels can be detected in people who practice regular physical activity, compared to levels in sedentary people.23,24 In our cohort, (although HDL cholesterol was not measured and therefore this hypothesis cannot be verified from our data), workers with heavy physical activity have the greatest life expectancy when their alcohol consumption is relatively low, while for sedentary workers the longest survival corresponds to an intake of quite heavy amounts of alcohol. This observation suggests that the benefits from alcohol and physical activity do not necessarily add together, and instead a saturation effect takes place.
The present study confirms once again the suitability of the preventive actions suggested by national and international organisations aimed at reducing alcohol consumption to moderate amounts, reducing or stopping smoking and increasing physical activity.
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