What is the relationship between alcohol intake and coronary heart disease?

Strong evidence consistently demonstrates that compared to non-drinkers, individuals who drink moderately have lower risk of coronary heart disease (CHD).

Insufficient evidence was available to determine if drinking patterns were predictive of risk of CHD, although there was moderate evidence to suggest that heavy or binge drinking is detrimental.

Related to the association between alcohol consumption and risk of coronary heart disease (CHD), six systematic reviews/meta-analyses were reviewed. This evidence included four methodologically strong meta-analyses (Bagnardi, 2008; Corrao, 2000; Di Castelnuovo, 2002; and Rimm, 1999); one methodologically neutral meta-analysis (Cleophas, 1999) and one systematic review that was methodologically neutral (Britton and McKee, 2000).

Overall, the evidence shows that compared to those who abstain from alcohol, regular light to moderate drinking can reduce the risk of CHD; whereas, heavy irregular or binge drinking increases risk of CHD. In a meta-analysis of 20 observational studies, Bagnardi et al, (2008) found significant differences in the alcohol intake dose response relationship to CHD risk in regular vs. irregular drinkers. These authors concluded that the consumption of alcohol on more than two days per week has a significant protective effect against CHD. Cleophas et al, (1999) found that alcohol consumption at one to four drinks per day reduced risk of mortality and CHD, while more than five drinks per day increased risk of mortality, and wine, beer and spirits were equally beneficial. Interestingly, a meta-analysis conducted by Corrao et al, (2000) of 43 cohort studies, found that in Mediterranean countries, protective effects were seen up to 145g per day, but in all other countries, the protective effects were only seen up to 80grams per day. Di Castelnuovo et al, (2000) compared wine and beer consumption in a meta-analysis of 26 international studies. The relative risks of cardiovascular disease (CVD) were 0.68 (95% CI: 0.59-0.77) and 0.78 (95% CI: 0.70-0.86) for consumption of wine and beer, respectively, relative to non-drinkers. Rimm (1999) concluded that based on a meta-analysis of 42 randomized controlled trials (RCTs), alcohol consumption per se, not other components of alcoholic beverages, was responsible for the lower risk of CHD among moderate drinkers. Furthermore, based on measures of high-density lipoprotein cholesterol (HDL-C), triglycerides (TG) and fibrinogen, to the degree documented in the meta-analysis, consumption of two standard drinks per day would lower a person’s risk of CHD by approximately 25%. According to Britton and Mckee (2000) a systematic review of international studies, not only alcohol quantity, but also drinking patterns such as binge drinking, influenced CVD risk.

Collectively, the research suggests that whereas binge drinking (more than three alcoholic drinks every one to two hours) has harmful effects, light to moderate alcohol consumption spread over several days of the week has beneficial effects relative to CVD risk. Therefore, for a given volume of alcohol within a moderate drinking range, it is better to distribute this volume evenly over several days, rather than consuming it in two to three days.

Bagnardi et al, 2008 (positive quality) conducted a meta-analysis to evaluate whether drinking pattern, defined by the frequency of drinking days as well as drinking intensity per drinking occasion, modified the effect of alcohol intake on the risk of CHD. A Medline search for articles published between 1966 and 2006 was done using keywords related to disease (coronary heart disease, coronary death, myocardial infarction, ischemic heart disease), exposure (quantity or dose of alcohol intake and pattern of alcohol drinking) and frequency of alcohol drinking (regular, irregular, problem drinking, alcoholic intoxication, heavy episodic drinking, hangover). The final meta-analysis included six studies, four cohort studies and two case-control studies. Compared with those who abstained from alcohol, regular heavy drinkers had a reduced risk of CHD (RR 0.75; 95% CI: 0.64, 0.89) and heavy irregular or binge drinkers had an increased risk (RR 1.10; 95% CI: 1.03, 1.17). The dose-response relationship between the amount of alcohol consumed and CHD risk also differed between regular and irregular heavy drinkers (P<0.047). A J-shaped curve was seen for irregular drinkers: The nadir and the last protective dose of 28g per week (RR 0.59; 95% CI: 0.53 to 0.65) and 131g per week (RR 0.85; 95% CI: 0.72 to 0.99) were obtained included drinkers who consumed alcohol for two days a week or less. Conversely, in people who consumed alcohol for more than two days a week a significant protective effect was seen even when drinking high amounts of alcohol.

Britton and McKee, 2000 (neutral quality), presents the key findings of a comprehensive systematic review that examined the relationship between heavy drinking and irregular (binge) drinking and sudden cardiovascular mortality. Six prospective cohort studies, conducted in Europe and the US, were included, as well as a number of case-control studies. The prospective follow-up ranged from 6.7 to 40 years. The authors found considerable evidence that binge drinkers as are at greater risk of cardiac arrhythmias and sudden cardiac death. The evidence also supported a temporal and dose-response relationship for sudden cardiac death and for fatal myocardial infarction (MI). The authors concluded that physiological evidence indicates that a causal relationship is biologically plausible, and that the effects of binge drinking are quite different from those seen with regular moderate and even heavy drinking.

Cleophas, 1999 (neutral quality), a meta-analysis of 20 international studies, assessed the relationship between MI and consumption of different types of alcoholic beverages, both in low doses (one to four drinks per day) and high doses (more than four drinks per day). Eight cohort studies were included that reported on the association between alcohol consumption irrespective of the type of drink and cardiovascular death, as well as twelve prospective cohort studies that reported on the risk of MI and specific types of alcoholic drinks. Small doses of alcohol were associated with a reduced risk of mortality and CHD, while more than five drinks per day increased the risk of mortality; wine, beer and spirits were equally beneficial.

Corrao et al, 2000 (positive quality) conducted a meta-analysis to evaluate the relationship between alcohol consumption and risk of CHD. Searches were conducted using Medline, Current Content, EMBASE, CAB, and Core Biomedical Collection, and a hand search of general reviews and meta-analyses published on issue was performed. The search included studies published between 1966 and 1998, and used the keywords for disease (coronary heart disease, coronary artery disease, coronary event, coronary death, myocardial infarction, ischemic heart disease and angina pectoris) and alcohol consumption (alcohol or ethanol and consumption, intake and drinking). The final sample included 43 cohort studies, eight case-control studies. Results from all 51 studies showed that a protective effect was evident up to 90g per day (RR=0.94; 95%CI: 0.90, 1.00), with harmful effects evidence at 113g per day (RR=1.08; 95%CI: 1.00, 1.16). These effects were modified when only the high quality studies (N=28) were considered, such that a protective effect was evident up to 72g per day (RR=0.96; 95%CI: 0.92, 1.00), and harmful effects were evident at 89g per day (RR=1.05; 95%CI: 1.00, 1.11). When examining data from females only, a protective effect evident up to 31g per day (RR=0.93; 95%CI: 0.87, 1.00), and harmful effects were evident at 52g per day (RR=1.12; 95%CI: 1.00, 1.26); for males, a protective effect was evident up to 87g per day (RR=0.94; 95%CI: 0.88, 1.00), and harmful effects were evident at 114g per day (RR=1.09; 95%CI: 1.00, 1.19). When looking at Mediterranean countries, protective effects were seen up to 145g per day (RR=0.76; 95%CI: 0.61, 1.00), but in all other countries as a whole, protective effects were only seen up to 80g per day (RR=0.93; 95%CI: 0.87, 1.00).

Di Castelnuovo et al, 2002 (positive quality), a meta-analysis of 26 international studies, studied the relationship between wine or beer consumption and CVD. From 13 studies, the RR of vascular disease associated with wine intake was 0.68 (95% CI: 0.59-0.77) relative to non-drinkers, and 10 studies supported a J-shaped relationship between different amounts of wine intake and vascular risk. A statistically significant inverse relationship was found up to a daily intake of 150ml of wine. From 15 studies, the relative risk of vascular disease associated with moderate beer consumption was 0.78 (95% CI: 0.70-0.86). However, no significant (NS) relationship between different amounts of beer intake and vascular risk was found.

Rimm et al, 1999 (positive quality) a meta-analysis of 42 experimental trials quantitatively examined the association between moderate alcohol intake and CHD risk. All of these trials offered the advantage of being randomized design, but all we relatively small. Trials were weighted according to number of study participants. Consumption of 30g alcohol per day (approximately two standard drinks) increased HDL levels by 4.0mg/dL, which was associated with an adjusted 16.8% decrease in CHD risk. Fibrinogen concentration also decreased by 7.5mg/dL, but the decrease was NS. Conversely, TG levels increased by an estimated 5.7% resulting in a 4.6% increase in CHD risk, which slightly attenuated the alcohol benefit. Taken together, the estimated changes in HDL, TG and fibrinogen levels induced by consumption of 30g of alcohol result in a 24.7% reduction in the risk of CHD.