Cigarette smoking and dementia: potential selection bias in the elderly

Epidemiology. 2008 May;19(3):448-50. doi: 10.1097/EDE.0b013e31816bbe14.


We conducted a systematic review of published prospective studies that estimated the association between smoking and the incidence of Alzheimer disease and dementia. The relative rate for smokers versus nonsmokers ranged from 0.27 to 2.72 for Alzheimer disease (12 studies) and from 0.38 to 1.42 for dementia (6 studies). The minimum age at entry (range: 55-75 years) explained much of the between-study heterogeneity in relative rates. We conjecture that selection bias due to censoring by death may be the main explanation for the reversal of the relative rate with increasing age.

Publication types

  • Comment
  • Review

MeSH terms

  • Aged
  • Dementia / epidemiology*
  • Dementia / etiology*
  • Humans
  • Middle Aged
  • Prospective Studies
  • Selection Bias
  • Smoking / adverse effects*