Original Article

Molecular Psychiatry (2015) 20, 778–785; doi:10.1038/mp.2014.187; published online 10 February 2015

Cigarette smoking and thinning of the brain’s cortex
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S Karama1,2, S Ducharme1,3,4,5, J Corley6, F Chouinard-Decorte1, J M Starr7,8, J M Wardlaw7,9,10, M E Bastin7,9,10 and I J Deary6,7

  1. 1Department of Neurology and Neurosurgery, McConnell Brain Imaging Center, Montreal Neurological Institute, McGill University, Montreal, QC, Canada
  2. 2Department of Psychiatry, Douglas Mental Health University Institute, McGill University, Verdun, QC, Canada
  3. 3Department of Psychiatry, McGill University Health Centre, Montreal, QC, Canada
  4. 4Department of Psychiatry and Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
  5. 5Department of Neurology, McLean Hospital, Harvard Medical School, Belmont, MA, USA
  6. 6Department of Psychology, University of Edinburgh, Edinburgh, UK
  7. 7Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK
  8. 8Department of Psychology, Alzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, UK
  9. 9Department of Radiology, Division of Neuroimaging Sciences, Brain Research Imaging Centre, University of Edinburgh, Edinburgh, UK

Correspondence: Dr S Karama, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Quebec, Canada H3A 2B4. E-mail: sherif.karama@mcgill.ca or ian.deary@ed.ac.uk

10SINAPSE (Scottish Imaging Network, A Platform for Scientific Excellence) collaboration

Received 21 August 2014; Revised 4 November 2014; Accepted 28 November 2014
Advance online publication 10 February 2015

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Abstract

Cigarette smoking is associated with cognitive decline and dementia, but the extent of the association between smoking and structural brain changes remains unclear. Importantly, it is unknown whether smoking-related brain changes are reversible after smoking cessation. We analyzed data on 504 subjects with recall of lifetime smoking data and a structural brain magnetic resonance imaging at age 73 years from which measures of cortical thickness were extracted. Multiple regression analyses were performed controlling for gender and exact age at scanning. To determine dose–response relationships, the association between smoking pack-years and cortical thickness was tested and then repeated, while controlling for a comprehensive list of covariates including, among others, cognitive ability before starting smoking. Further, we tested associations between cortical thickness and number of years since last cigarette, while controlling for lifetime smoking. There was a diffuse dose-dependent negative association between smoking and cortical thickness. Some negative dose-dependent cortical associations persisted after controlling for all covariates. Accounting for total amount of lifetime smoking, the cortex of subjects who stopped smoking seems to have partially recovered for each year without smoking. However, it took ~25 years for complete cortical recovery in affected areas for those at the mean pack-years value in this sample. As the cortex thins with normal aging, our data suggest that smoking is associated with diffuse accelerated cortical thinning, a biomarker of cognitive decline in adults. Although partial recovery appears possible, it can be a long process.