The consumption of heavy alcohol has been linked to an increased risk of acute ischemic stroke and hemorrhagic stroke. Previous studies have had conflicting results on the moderate consumption of alcohol and stroke risk.1-3 A meta-analysis and systematic review by Patra and colleagues showed that heavy alcohol consumption increases the relative risk of any stroke while light or moderate alcohol consumption may be protective against ischemic stroke.4 The authors of this study attempt to fill a gap in knowledge regarding variance between stroke risk and alcohol consumption. They specifically looked at whether stroke risk associated with alcohol consumption is stable over time. 


The authors analyzed 11,644 members of the population-based Swedish Twin Registry born 1886-1925 with alcohol data before the age of 60. The interaction of midlife alcohol consumption by age at stroke was evaluated in Cox regression and analyses of monozygotic twins were utilized. It was found that 29% of the cohort developed stroke. When comparing light drinkers to heavy drinkers, heavy drinkers were found to have a greater risk of stroke (HR = 1.34, p=0.02). Midlife heavy drinkers were at high risk from baseline until age 75 when hypertension and diabetes grew to being the more relevant risk factors. The authors further analyzed monozygotic twin pairs and showed prolongation of time to stroke for non-drinkers by 2.07 years (p=0.11), for light drinkers by 0.77 years (p=0.54), and for moderate drinkers by 1.15 years (p=0.47) compared to very-light drinkers. The results for heavy drinkers showed decreased time to stroke by 5.68 years (p=0.029).

This study primarily expands on previous research in the assessment of the risk of stroke attributable to alcohol consumption. The results show that risk of stroke associated with heavy drinking in midlife is at least comparable to stroke risk associated with risk factors like diabetes or hypertension; however, the age when those risk factors are relevant do vary. Interestingly, the authors find that the risk of hemorrhagic stroke is higher for heavy alcohol consumers relative to ischemic stroke. Based on a previous review from the cardiac literature, the authors postulate that alcohol can give some protection from ischemic stroke by improving thrombolytic profiles and increasing blood flow. A search in the medical literature yields previous studies that demonstrate the beneficial effects of alcohol in cardiovascular health however there were very few studies that investigated the effects of alcohol consumption and its protective/harmful effect on neurons during an ischemic stroke. The stroke community should make more targeted efforts on educating younger patients (midlife) on alcohol consumption and its risks going forward. However, there remains a need for further studies on different populations around the globe to be conducted (as this was based on a Swedish cohort) to ensure that the results can be generalizable.

References
1. Caicoya M, Rodriguez T, Corrales C, Cuello R, Lasheras C: Alcohol and stroke. A community case control study in Astrurias, Spain. J Clin Epidemiol 1999, 52:677-684.
2. Donahue RP, Abbott RD, Reed DM, Yano K: Alcohol and hemorrhagic stroke: the Honolulu Heart Program. JAMA 1986, 255:2311-2314.
3. Thrift A, Donnan G, McNeil J: Heavy drinking, but not moderate or intermediate drinking, increases the risk of intracerebral hemorrhage. Epidemiol 1999, 10:307-312
4. Patra J, Taylor B, Irving H, Roerecke M, Baliunas D, Mohapatra S, et al. Alcohol consumption and the risk of morbidity and mortality for different stroke types-a systematic review and meta-analysis. BMC public health. 2010;10:258