Smoking and increased Alzheimer's disease risk: A review of potential mechanisms

Abstract

Background Cigarette smoking has been linked with both increased and decreased risk for Alzheimer’s disease (AD). This is relevant for the US military because the prevalence of smoking in the military is approximately 11% higher than in civilians. Methods Systematic review of published studies on the association between smoking and increased risk for AD, and preclinical and human literature on the relationships between smoking, nicotine exposure and AD-related neuropathology. Original data from comparisons of smoking and never-smoking cognitively normal elders on in vivo amyloid imaging are also presented. Results Overall, the literature indicates that former/active smoking is related to a significantly increased risk for AD. Cigarette smoke/smoking is associated with AD neuropathology in preclinical models and humans. Smoking-related cerebral oxidative stress is a potential mechanism promoting AD pathophysiology and increased risk for AD. Conclusions A reduction in the incidence of smoking will likely reduce the future prevalence of AD.

Effect of smoking cessation on the risk of dementia: a longitudinal study

“…Few studies have shown that nicotine may actually improve short‐term cognitive performance7, 30 and inhibit amyloid formation 31, 32. On the other hand, various other studies have shown that smoking is a risk factor for Alzheimer's disease, namely due to reactive oxygen species produced by smoking 33, 34, 35, 36, 37. Smoking directly delivers reactive oxidant species from the cigarette into the bloodstream, promotes the generation of endogenous reactive oxidant species and causes weakening of antioxidant defense systems 38, 39.…”

Biomarker assessment of tobacco smoking exposure and risk of dementia death: pooling of individual participant data from 14 cohort studies

“…As indicated, imaging studies suggest that, compared with abstainers, smokers have a greater degree of brain atrophy and lower grey matter density in selected areas 3. Other potential explanations include the observation that smoking exposure has a deleterious influence on the cardiovascular system, including increased coagulation of blood platelets, decreased coronary flow velocity reserves, accelerated atheroma genesis and endothelial dysfunction 15.…”

“…Small-scale, high-resolution studies showing that smokers, relative to their non-smoking counterparts, have a greater degree of brain atrophy and lower grey matter density in selected areas3 have prompted a series of large, population-based investigations of the link between this health behaviour and dementia risk. While these generally show that cigarette smokers typically experience higher rates of future dementia,3 4 with the evidence being based exclusively on self-reported smoking data, it has not been possible to explore the thresholds at which this exposure elevates risk.…”

Perceptions of harm from electronic-cigarette use among a sample of US Navy personnel

“…Additionally, the HBM has been shown to be beneficial in assessing perceived harms and cessation intentions in relation to EC use 4 . The prevalence of tobacco use within the U.S. military is markedly higher than its civilian counterpart 5,6 . The U.S. Navy closely mirrors the overall U.S. military in smoking frequency prevalence (8.3%, 8.2% infrequent smokers; 12.6%, 12.6% light/moderate smokers; 3.4%, 3.2% heavy smokers; respectively) 6 .…”