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Smoking Is Associated With Reduced Cortical Regional Gray Matter Density in Brain Regions Associated With Incipient Alzheimer Disease

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Objectives

The results of observational studies suggest that smoking increases the risk of Alzheimer disease (AD). The authors designed this study to determine if older people who smoke have decreased gray matter density in brain regions associated with incipient AD.

Methods

The authors recruited 39 pairs (N = 78) of smokers/never-smokers 70 to 83 years of age who were matched for age, sex, education, and handedness. Participants were free of clinically significant cognitive impairment, depression, stroke, or other serious medical conditions. Gray matter density was determined by voxel-based morphometry using statistical parametric mapping of T1-weighted magnetic resonance images.

Results

Smokers had decreased gray matter density in the posterior cingulum and precuneus (bilateral), right thalamus, and frontal cortex (bilateral) compared with never-smokers.

Conclusions

Smoking is associated with decreased gray matter density in brain regions previously associated with incipient AD. Longitudinal investigations are required to clarify whether these changes are progressive in nature.

Section snippets

Participants

Subjects were recruited from various sources, including an ongoing community study of older men,18 general practices in metropolitan Western Australia, and advertisements in the local media. “Smokers” had to 1) consume a minimum of 5 cigarettes daily (or equivalent in loose tobacco) during the previous 12 months; 2) be 70 years of age or older; 3) be fluent in written and spoken English; 4) have a Mini-Mental State Exam score of ≥24;19 5) be free of clinically significant depressive symptoms

RESULTS

Forty-one smokers were available for this study. Two subjects had to be excluded from the study: one because of a brain tumor and one because of widespread subcortical lesions. Thus, 39 pairs were included in the analysis (39 smokers and 39 individually matched never-smokers). Participants’ ages ranged from 70 to 83 years (mean ± SD: 75.0 ± 3.4 years for smokers and 75.7 ± 3.2 years for never-smokers), 64% (25/39 pairs) were males, 91% were right handed, and 38% had a high school or university

DISCUSSION

Our results confirm that older adults who smoke have decreased gray matter densities in areas previously associated with chronic smoking and incipient or mild AD.15., 16., 25. Compared with controls who had never smoked, the most noticeable and consistent losses of gray matter density among smokers involved the posterior cingulum and precuneus, precentral gyri, and right thalamus. To our knowledge, the association between smoking and regional gray matter changes has not been studied previously

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    The authors thank their research staff for data collection and management and the participants for volunteering their time.

    This work was supported by National Health and Medical Research Council of Australia project grant 254572. GJG is partly supported by the Fundação de Amparoà Pesquisa do Estado de São Paulo (FAPESP project grant 03/11794-6).

    None of the authors have any actual or potential conflict of interest to declare.

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