Moderate Alcohol Intake May Reduce the Risk of Developing Multiple Sclerosis, but Smoking Cessation Is Also Important

Amid conflicting evidence, Swedish researchers have found an association between multiple sclerosis (MS) and alcohol consumption, but the benefits of regular moderate alcohol intake in reducing the risk of MS may be attenuated by smoking.

According to Swedish researchers Drs. Hedström, Hillert, Olsson, and Alfredsson, regular alcohol consumption may reduce the risk of developing multiple sclerosis (MS). This finding contradicts extensive earlier research including 2 case-control studies and 1 large prospective study.

Previous studies do not support the findings of Hedström et al. A 1993 study of 108 patients with MS found no association with alcohol abuse and the risk of developing MS. A 2006 case-control study of 210 patients with MS and 210 matched control subjects revealed higher rates of hard liquor consumption in patients with MS. Additionally, a 25-year study of approximately 100,000 female nurses found no association between total alcohol consumption and the risk of developing MS.

Despite the large number of participants in the 25-year study of female nurses, researchers report that the number of participants consuming 15 or more grams of alcohol daily was too low to detect a preventive effect of alcohol consumption in MS. The researchers also noted that experimental limitations and small sample sizes limited the relevance of the 1993 and 2006 studies.

Given that several autoimmune diseases are less likely to occur in alcohol drinkers than in nondrinkers, the researchers hypothesized that a large analysis might also detect a reduction in the risk of MS with regular alcohol intake.

To evaluate the hypothesis, researchers evaluated data from 2 prospective studies: Epidemiological Investigation of Multiple Sclerosis (EIMS) and Genes and Environment in Multiple Sclerosis (GEMS). In GEMS, data came from 5874 patients with MS and 5246 patients in a control group. Data from another prospective study, EIMS, included questionnaire results from 1301 potential MS patients and 2826 age-, sex-, and location-matched controls across 40 study centers in Sweden.

In both studies, women and men who consumed alcohol regularly had a significantly lower risk of developing MS than nondrinkers. Using data from EIMS, the odds ratio of developing MS in women consuming at least 112 g of alcohol per week was 0.6 (95% CI; 0.4 to 1.0); in men consuming at least 168 g of alcohol weekly, the odds ratio of developing MS was 0.5 (95% CI; 0.2 to 1.0) compared with nondrinkers. An analysis of data from GEMS revealed similar findings.

Another important finding is that smoking eliminated the protective effect of regular alcohol consumption and increased the risk of developing MS in nondrinkers. By smoking, regular drinkers increased the risk of MS by 40%, reducing the benefit of regular alcohol consumption (P ≤.001). Moreover, smokers who did not drink had the highest rate of MS—nearly double that of nonsmoking drinkers (odds ratio: 1.8 [EIMS data] to 1.9 [GEMs data]; P <.001, both comparisons).

Conflicting evidence may warrant caution in recommending regular alcohol intake as a preventive measure against MS. In addition, patients who read headlines about the preventive effects of alcohol on MS should know that the benefits of moderate alcohol may be reduced by smoking. As the results of this trial show, smoking cessation may be as important as encouraging moderate alcohol consumption for patients at risk for this debilitating disease.