Smoking and the risk of dementia in the oldest‐old: The Monzino 80‐plus study

Abstract

AbstractBackgroundNicotine is a cholinergic agonist that can enhance short‐term cognitive performance. After initial findings suggesting a possible protective effect of smoking against dementia, subsequent research has pointed out smoking as a risk factor for dementia and Alzheimer’s disease. However, very few data are available on this relationship in the oldest‐old. Objectives: To explore the association of smoking with the development of dementia in advanced age in a prospective population‐based study of 80‐years or older residents in Varese province, Italy (Monzino 80‐plus Study).MethodInformation on smoking habit was obtained from the subject and/or a primary informant, mostly a family member, using a standardized questionnaire. Diagnosis of dementia fulfilled DSM‐IV criteria. Logistic regression and Cox proportional hazard models were used to investigate cross sectional and longitudinal associations between smoking and dementia risk.ResultThe initial population consisted of 2,193 individuals (mean age: 90.2 years; women: 72.7%). At first visit oldest‐old who had never smoked represented the large majority of the population (1778, 81.1%), while current smokers were very few (n=49, 2.2%). On average, they currently smoked 9.7±7.9 cigarettes daily, started smoking at 22.8±11.7 years of age, and had been smoking for 67.1±10.3 years. Former smokers (n=366; 16.7%) had quit smoking on average 29.6±18.0 years before initial interview. Prevalence of dementia was lower among current smokers (18.4%) compared to never smokers (40.0%; p=0.0036), but this difference was no longer significant after adjustment for age, sex, and education (adjusted p=0.2435). There were 1,138 individuals without dementia at first visit with at least one follow‐up available (mean age: 88.4 years; women: 69.2%). In the following 15.5 years, current smokers (n=28) had a higher occurrence of dementia (60.7%) than never smokers (50.1%; age, sex, and education adjusted HR: 1.30, 95% CI: 0.80‐2.12, p=0.2913) or non‐smokers (never and former) (46.9%; age, sex, and education adjusted HR: 1.34, 95% CI: 0.83‐2.18, p=0.2349). The low proportion of current smokers limited the possibility to investigate the effect of smoking on dementia incidence.ConclusionSmoking habit is very uncommon among oldest‐old and it was not significantly associated with the risk of dementia either in cross sectional or longitudinal analysis.