title: Combined impact of smoking and heavy alcohol use on cognitive decline in early old age: Whitehall II prospective cohort study.
abstract: BACKGROUND
  Identifying modifiable risk factors for cognitive decline may inform prevention of dementia.
  
  
  OBJECTIVE
  To examine the combined impact of cigarette smoking and heavy alcohol consumption on cognitive decline from midlife.
  
  
  METHODS
  Prospective cohort study (Whitehall II cohort) with three clinical examinations in 1997/99, 2002/04 and 2007/09. Participants were 6473 adults (72% men), mean age 55.76 years (s.d. = 6.02) in 1997/99. Four cognitive tests, assessed three times over 10 years, combined into a global z-score (mean 0, s.d. = 1).
  
  
  RESULTS
  Age-related decline in the global cognitive score was faster in individuals who were smoking heavy drinkers than in non-smoking moderate alcohol drinkers (reference group). The interaction term (P = 0.04) suggested that the combined effects of smoking and alcohol consumption were greater than their individual effects. Adjusting for age, gender, education and chronic diseases, 10-year decline in global cognition was -0.42 z-scores (95% CI -0.45 to -0.39) for the reference group. In individuals who were heavy alcohol drinkers who also smoked the decline was -0.57 z-scores (95% CI -0.67 to -0.48); 36% faster than the reference group.
  
  
  CONCLUSIONS
  Individuals who were smokers who drank alcohol heavily had a 36% faster cognitive decline, equivalent to an age-effect of 2 extra years over 10-year follow-up, compared with individuals who were non-smoking moderate drinkers.
authors.affiliation: Department of Epidemiology and Public Health, University College London, UK. g.hagger-johnson@ucl.ac.uk
authors.forename: Gareth
authors.initials: G
authors.lastname: Hagger-Johnson
authors.forename: Séverine
authors.initials: S
authors.lastname: Sabia
authors.forename: Eric John
authors.initials: EJ
authors.lastname: Brunner
authors.forename: Martin
authors.initials: M
authors.lastname: Shipley
authors.forename: Martin
authors.initials: M
authors.lastname: Bobak
authors.forename: Michael
authors.initials: M
authors.lastname: Marmot
authors.forename: Mika
authors.initials: M
authors.lastname: Kivimaki
authors.forename: Archana
authors.initials: A
authors.lastname: Singh-Manoux
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000523:psychology*; D000428:Alcohol Drinking / Q000009:adverse effects*; D003071:Cognition; D003072:Cognition Disorders / Q000175:diagnosis / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term; D008875:Middle Aged; D009483:Neuropsychological Tests; D011340:Problem Solving; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*