Between May 1991 and January 1994, a sample of 10
600 men aged 50-59 years was examined in one centre in Northern Ireland (Belfast; n=2745) and three centres in France—Lille in the north (n=2633), Strasbourg in the east (n=2612), and Toulouse in the south west (n=2610). Of these 10
600 participants, 842 (7.9%) were excluded because of a medically diagnosed history of angina pectoris or myocardial infarction, or because of chest pain at entry according to the Rose questionnaire. A total of 317 (3.0%) men were lost to follow-up after 10 years, 215 (2%) refused to continue participating in the study, and 653 (6.1%) died in the course of follow-up. The proportion of refusals and participants lost to follow-up was similar in Belfast and the French centres (150/2745 (5.5%) and 382/10
600 (3.6%), respectively). The number of men included was 9778 in total: 2405 and 7373 in Belfast and in the French centres, respectively.
Patterns of alcohol consumption
A total of 1456 (60.5%) of the 2405 men in Belfast and 6679 (90.6%) of the 7373 men at the French centres reported drinking alcohol at least once a week. Only half of the drinkers in Belfast were regular drinkers compared with most alcohol drinkers in France (1229/2405 (51.1%) and 6646/7373 (90.1%), respectively), whereas 227 (9.4%) men in Belfast and 33 (0.5%) in France were binge drinkers (table 1). Among drinkers, 5008 (75%) in France drank alcohol every day, whereas in Belfast only 173 (11.9%) drank daily and 1052 (72.2%) drank on one, two, or three days a week. The proportion of men in Belfast who drank alcohol was two to threefold higher on Fridays (937/2405 (39%)) and Saturdays (1231/2405 (51%)) compared with the other days of the week.
Table 1 Patterns of alcohol consumption in Belfast and in three French centres
Drinkers in Belfast mainly consumed beer (1100/1456 (75.5%)), followed by spirits (892/1456 (61.3%)), with a small minority consuming wine (399/1456 (27.4%)). In stark contrast, wine was predominantly consumed in the French centres (6134/6679 (91.8%)), followed by liquor (4941/6679 (74.0%)) and, less frequently, beer (3770/6679 (56.4%)).
In France, the proportions of non-drinkers were comparable across centres: 8.2% (n=199) in Strasbourg, 9.7%, (n=243) in Toulouse, and 10.3% (n=252) in Lille. Among drinkers, the numbers of men who drank every day were similar in Strasbourg, Toulouse, and Lille (n=1689 (75.3%), n=1631 (72.2%), and n=1688 (77.3%), respectively). The most significant difference between the centres was in the type of alcohol consumed: in Toulouse 83% of alcohol consumed was as wine, whereas in Strasbourg and Lille only 63% and 61%, respectively, was consumed as wine, most of the rest of the alcohol being provided by beer.
Amount of alcohol consumed
Among regular drinkers, the total volume of alcohol consumed over a week was practically identical in Belfast and in France (281.7 g (SD 279.2) v 254.6 g (198.1); table 1). Mean daily alcohol consumption was 22.1 g in Belfast and 32.8 g in France. However, the alcohol volume tended to be consumed on one or two days in participants from Belfast and throughout the week in people enrolled at the three French centres. Mean alcohol consumption was 2-3 fold higher at weekends in Belfast than in France. On Fridays, drinkers in Belfast consumed on average 61.1 g (74.3) of alcohol compared with 33.7 g (29.8) in France, and on Saturdays the respective means were 91.4 g (84.3) and 41.1 g (31.8). Among drinkers in France, the quantities of alcohol consumed daily were similar in Strasbourg, Toulouse, and Lille (36.6 g/day, 33.0 g/day, and 39.2 g/day, respectively).
Baseline characteristics stratified by level of alcohol consumption are shown in table 2. Irrespective of centre, higher alcohol consumption was associated with increased levels of smoking; higher total cholesterol, high density lipoprotein cholesterol, apolipoprotein A-1, and triglyceride levels; and raised blood pressure (P=0.001 for all). In France, non-drinkers were more likely to be receiving treatment for diabetes (P=0.003), and higher alcohol consumption was associated with higher body mass index, waist circumference, and apolipoprotein B levels. Low educational level was associated with non-drinking in France but with the heaviest drinking in Belfast (P=0.001 for both).
Table 2 Baseline characteristics according to level of alcohol consumption in Belfast and the French centres
Incidence of ischaemic heart disease
After 10 years’ follow-up, 322 (3.3%) incident hard coronary events (127 (5.3%) v 195 (2.6%) in Belfast and the French centres, respectively) and 361 (3.7%) incident angina events were identified (120 (5.0%) v 241 (3.3%), respectively). In France, the numbers of hard coronary events were similar in the three centres: 69 (2.8%), 66 (2.6%), and 60 (2.5%) in Strasbourg, Toulouse, and Lille, respectively. A comparable picture was observed for angina events: 74 (3.1%), 89 (3.6%), and 78 (3.2%) in Strasbourg, Toulouse, and Lille, respectively.
Annual incidence of hard coronary events per 1000 participants was 5.63 (95% confidence interval 4.69 to 6.69) in Belfast and 2.78 (95% CI 2.41 to 3.20) in the French centres. Annual incidence of angina was 5.46 (95% CI 4.53 to 6.54) and 3.49 (95% CI 3.06 to 3.96) per 1000 participants, respectively.
In all French centres combined, the proportion of individuals who experienced a hard coronary event differed significantly across categories of alcohol volume (P=0.02; table 3). This relation was not observed in Belfast. In both countries, the highest incidence of hard coronary events was noted in the non-drinking groups (6.4% in Belfast and 4.6% in the French centres). Whatever the category of alcohol consumption, the proportions of individuals who experienced a hard coronary event or an angina event were always higher in Belfast than in the French centres.
Table 3 Incident ischaemic heart disease events according to level of alcohol consumption in Belfast and the French centres
Alcohol consumption and ischaemic heart disease
After multivariate adjustment for centre or country and classic cardiovascular risk factors (age, tobacco consumption, years of education, level of physical activity, systolic blood pressure, apolipoprotein A-1 and apolipoprotein B concentration, waist circumference, and treatment for hypertension, diabetes, and dyslipidaemia), alcohol consumption patterns remained associated with the occurrence of hard coronary events, regardless of country (Belfast P<0.02; France P<0.02; and in all centres P<0.001; global Wald χ2 test; fig 1 ). Conversely, alcohol intake was not associated with incidence of angina pectoris.
Fig 1 Hazard ratios for ischaemic heart disease in binge drinkers, never drinkers, and former drinkers in Belfast and in three centres in France, with regular drinkers as reference. Hazard ratios are adjusted for age, centre or country, tobacco consumption, (more ...)
The risk of hard coronary events in binge drinkers and in never drinkers was very similar and was about twofold higher than in regular alcohol drinkers. The hazard ratio for hard coronary events in binge drinkers compared with regular drinkers was 1.81 (95% CI 1.05 to 3.11) in Belfast and 1.93 (95% CI 0.46 to 7.40) in the French centres. In all centres combined, the hazard ratio for developing hard coronary events compared with regular drinkers was 2.03 (95% CI 1.41 to 2.94) in never drinkers and 1.97 (95% CI 1.21 to 3.22) in binge drinkers. This difference between never drinkers and binge drinkers was not significant (P=0.91; Wald χ2 test). In the entire cohort, the hazard ratio for former drinkers in comparison with regular drinkers was 1.57 (95% CI 1.11 to 2.21). There was no significant difference between the hazard ratios of former drinkers and never drinkers. Both in Belfast and in the French centres, the volume of alcohol intake and the frequency of alcohol consumption were not associated with the risk of developing hard coronary events in regular drinkers (fig 2 and fig 3).
Fig 2Hazard ratios for hard coronary events according to volume of alcohol consumption in regular drinkers compared with alcohol consumption of 1-24 g/day. Hazard ratios are adjusted for age, centre or country, tobacco consumption, years of education, (more ...)
Fig 3Hazard ratios for hard coronary events according to weekly frequency of alcohol consumption in regular drinkers compared with alcohol consumption of 1 day/week. Hazard ratios are adjusted for age, centre or country, tobacco consumption, (more ...)
We performed regression analyses with polynomial models (quadratic and cubic) using alcohol intake as a continuous variable to examine for possible non-linear relations between alcohol volume and the occurrence of hard coronary events. The parsimonious linear specification was adopted because the second and third order polynomial terms were not consistently significant, whatever the model. For an increase of 10 g in the amount of alcohol consumed a day, the risk of developing hard coronary events in regular drinkers was 1.04 (95% CI 0.97 to 1.12; P=0.31) in Belfast, 0.98 (95% CI 0.93 to 1.04; P=0.59) in the French centres, and 1.01 (95% CI 0.96 to 1.05; P=0.73) in the whole cohort (P=0.11 for interaction centre × alcohol volume).
Wine drinking compared to not drinking wine was associated with a lower risk of hard coronary events in regular alcohol drinkers after multivariate adjustment (age, centre, tobacco consumption, years of education, level of physical activity, systolic blood pressure, apolipoprotein A-1, apolipoprotein B, waist circumference, treatment for hypertension, diabetes and dyslipidaemia), whereas no significant association was found for beer compared with no beer or other alcoholic beverages versus no other alcoholic beverages (table 4). Further adjustment for volume of alcohol consumed or for weekly frequency of alcohol consumption did not change the results significantly. Interactions between types of alcohol drinks (wine v beer, wine v other drinks, and beer v other drinks) were not significant. Two by two comparisons showed significant differences in the risk of hard coronary events between wine and beer drinking and between wine and other types of alcohol when all centres were pooled.
Table 4 Hazard ratios for hard coronary events in regular drinkers according to type of drink
Alcohol consumption and ischaemic heart disease in Belfast versus France
The risk of developing ischaemic heart disease in Belfast in comparison with the French centres for the whole cohort (drinkers and non-drinkers) is given in table 5. Hazard ratios gradually decreased after successive adjustment for classic risk factors (age, centre, tobacco consumption, years of education, physical activity, systolic blood pressure, apolipoprotein A-1 and apolipoprotein B concentration, waist circumference, and treatment for hypertension, diabetes, and dyslipidaemia), drinking status, and wine drinking. The decreasing trend was more substantial for hard coronary events than for angina pectoris.
Table 5 Hazard ratios for ischaemic heart disease in Belfast in relation to the French centres
Among non-drinkers in the cohort, the hazard ratios for hard coronary events and angina pectoris in Belfast compared with in France were 1.36 (95% CI 0.88 to 2.08; P=0.16) and 1.25 (95% CI 0.76 to 2.06; P=0.37) in crude analyses. After multivariate adjustment for classic risk factors, these hazard ratios were 1.27 (95% CI 0.77 to 2.09; P=0.35) and 1.26 (95% CI 0.69 to 2.30; P=0.44), respectively.
After multivariate adjustment for classic risk factors and alcohol consumption, the hazard ratio for hard coronary events among regular drinkers in Belfast compared with the French centres was notably reduced, from 1.61 (95% CI 1.16 to 2.22) to 1.02 (95% CI 0.66 to 1.57).