Midlife cigarette smoking of two packs per day or more portends an elevated risk for overall dementia, Alzheimer disease, and vascular dementia in later life.
Studies of smoking and dementia risk have yielded mixed results: Some data suggest that the risk for neurodegenerative illness is reduced by smoking, whereas other data suggest a positive correlation between amount of cigarette smoking and risk for Alzheimer disease (AD). In this retrospective analysis of prospectively collected data, more than 20,000 adults completed a survey regarding smoking habits between ages 50 and 60. Approximately 20 years later, they were assessed for dementia; more than 5000 of them received diagnoses of dementia by neurologists, neuropsychologists, or internists.
Compared with nonsmokers, those who reported heavy smoking (2 packs of cigarettes per day) in midlife demonstrated an elevated risk for later dementia diagnosis, even after adjustments for known risk factors for cerebrovascular disease and dementia, including hypertension, hyperlipidemia, stroke, age, education, and alcohol use (adjusted hazard ratio, 2.14). For the most part, amount of smoking correlated with dementia risk. However, those who had reported former smoking or smoking less than half a pack per day in midlife did not have an elevated risk for dementia compared with nonsmokers. Heavy midlife smoking conferred similar risks for AD and for vascular dementia (VaD) diagnosed by neurologists or neuropsychologists (adjusted HRs, 2.57 and 2.72, respectively), but AD and VaD risk did not correlate linearly with amount of smoking.
Comment: Limitations of this study include the lack of clearly defined diagnostic criteria for dementia (given the authors’ reliance on ICD-9 diagnostic coding) and the challenges inherent in using self-reported survey data to assess a risky behavior (tobacco use). Additionally, many participants may have started smoking, altered the amount of smoking, or quit smoking during the 20-year interval between the survey and ascertainment of diagnoses. Nonetheless, these findings add a new layer to the well-established body of literature associating heavy cigarette smoking with negative health consequences. Middle-aged patients can be counseled that smoking cessation may benefit not only vascular health but cognitive health as well.
Published in Journal Watch Neurology November 16, 2010
Citation(s):
Rusanen M et al. Heavy smoking in midlife and long-term risk of Alzheimer disease and vascular dementia. Arch Intern Med 2010 Oct 25; [e-pub ahead of print]. (http://dx.doi.org/10.1001/archinternmed.2010.393)
