title: Differing association of alcohol consumption with different stroke types: a systematic review and meta-analysis.
abstract: Whether light-to-moderate alcohol consumption is protective against stroke, and whether any association differs by stroke type, is controversial. We conducted a meta-analysis to summarize the evidence from prospective studies on alcohol drinking and stroke types.
  
  
  
  Studies were identified by searching PubMed to September 1, 2016, and reference lists of retrieved articles. Additional data from 73,587 Swedish adults in two prospective studies were included. Study-specific results were combined in a random-effects model.
  
  
  
  The meta-analysis included 27 prospective studies with data on ischemic stroke (25 studies), intracerebral hemorrhage (11 studies), and/or subarachnoid hemorrhage (11 studies). Light and moderate alcohol consumption was associated with a lower risk of ischemic stroke, whereas high and heavy drinking was associated with an increased risk; the overall RRs were 0.90 (95 % CI, 0.85-0.95) for less than 1 drink/day, 0.92 (95 % CI, 0.87-0.97) for 1-2 drinks/day, 1.08 (95 % CI, 1.01-1.15) for more than 2-4 drinks/day, and 1.14 (95 % CI, 1.02-1.28) for more than 4 drinks/day. Light and moderate alcohol drinking was not associated with any hemorrhagic stroke subtype. High alcohol consumption (>2-4 drinks/day) was associated with a non-significant increased risk of both hemorrhagic stroke subtypes, and the relative risk for heavy drinking (>4 drinks/day) were 1.67 (95 % CI, 1.25-2.23) for intracerebral hemorrhage and 1.82 (95 % CI, 1.18-2.82) for subarachnoid hemorrhage.
  
  
  
  Light and moderate alcohol consumption was inversely associated only with ischemic stroke, whereas heavy drinking was associated with increased risk of all stroke types with a stronger association for hemorrhagic strokes.
authors.affiliation: Unit of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, SE-17177, Stockholm, Sweden. susanna.larsson@ki.se.|Stroke Research Group, Neurology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0QQ, UK. susanna.larsson@ki.se.
authors.forename: Susanna C
authors.initials: SC
authors.lastname: Larsson
authors.affiliation: Unit of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, SE-17177, Stockholm, Sweden.
authors.forename: Alice
authors.initials: A
authors.lastname: Wallin
authors.affiliation: Unit of Nutritional Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, SE-17177, Stockholm, Sweden.
authors.forename: Alicja
authors.initials: A
authors.lastname: Wolk
authors.affiliation: Stroke Research Group, Neurology Unit, Department of Clinical Neurosciences, University of Cambridge, Cambridge, CB2 0QQ, UK.
authors.forename: Hugh S
authors.initials: HS
authors.lastname: Markus
mesh_terms: D000328:Adult; D000428:Alcohol Drinking / Q000009:adverse effects*; D005260:Female; D006801:Humans; D020300:Intracranial Hemorrhages / Q000453:epidemiology / Q000209:etiology; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology* / Q000209:etiology*; D013548:Sweden
keywords: Alcohol consumption; Meta-analysis; Prospective studies; Stroke