Meta-Analysis

. 2015 Dec 15;5(12):e008393.

doi: 10.1136/bmjopen-2015-008393.

Effect of smoking on physical and cognitive capability in later life: a multicohort study using observational and genetic approaches

Affiliations

¹ School of Social and Community Medicine, University of Bristol, Bristol, UK.
² School of Social and Community Medicine, University of Bristol, Bristol, UK Division of Health Sciences, Warwick Medical School, University of Warwick, Warwick, UK Department of Mathematics and Statistics, Lancaster University, Lancaster, UK.
³ MRC Unit for Lifelong Health and Ageing at UCL, London, UK.
⁴ Population, Policy and Practice, UCL Institute of Child Health, University College London, London, UK.
⁵ Department of Psychology, University of Edinburgh, Edinburgh, UK.
⁶ Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK.
⁷ Department of Psychology, University of Edinburgh, Edinburgh, UK Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK.
⁸ School of Social and Community Medicine, University of Bristol, Bristol, UK University of Bristol/University Hospitals Bristol NHS Foundation Trust National Institute for Health Research Bristol Nutrition Biomedical Research Unit, University of Bristol, Bristol, UK.
⁹ MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK.
¹⁰ ISER, University of Essex, Essex, UK Department of Epidemiology and Public Health, UCL, London, UK.
¹¹ MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK National Institute for Health Research Nutrition Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK National Institute for Health Research Musculoskeletal Biomedical Research Unit, University of Oxford, Oxford, UK.
¹² Department of Epidemiology and Public Health, UCL, London, UK.

PMID: 26671949
PMCID: PMC4679991
DOI: 10.1136/bmjopen-2015-008393

Meta-Analysis

Effect of smoking on physical and cognitive capability in later life: a multicohort study using observational and genetic approaches

Teri-Louise North et al. BMJ Open. 2015.

. 2015 Dec 15;5(12):e008393.

doi: 10.1136/bmjopen-2015-008393.

Authors

Affiliations

¹ School of Social and Community Medicine, University of Bristol, Bristol, UK.
² School of Social and Community Medicine, University of Bristol, Bristol, UK Division of Health Sciences, Warwick Medical School, University of Warwick, Warwick, UK Department of Mathematics and Statistics, Lancaster University, Lancaster, UK.
³ MRC Unit for Lifelong Health and Ageing at UCL, London, UK.
⁴ Population, Policy and Practice, UCL Institute of Child Health, University College London, London, UK.
⁵ Department of Psychology, University of Edinburgh, Edinburgh, UK.
⁶ Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK.
⁷ Department of Psychology, University of Edinburgh, Edinburgh, UK Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK.
⁸ School of Social and Community Medicine, University of Bristol, Bristol, UK University of Bristol/University Hospitals Bristol NHS Foundation Trust National Institute for Health Research Bristol Nutrition Biomedical Research Unit, University of Bristol, Bristol, UK.
⁹ MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK.
¹⁰ ISER, University of Essex, Essex, UK Department of Epidemiology and Public Health, UCL, London, UK.
¹¹ MRC Lifecourse Epidemiology Unit, University of Southampton, Southampton, UK National Institute for Health Research Nutrition Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK National Institute for Health Research Musculoskeletal Biomedical Research Unit, University of Oxford, Oxford, UK.
¹² Department of Epidemiology and Public Health, UCL, London, UK.

PMID: 26671949
PMCID: PMC4679991
DOI: 10.1136/bmjopen-2015-008393

Abstract

Objectives: The observed associations between smoking and functional measures at older ages are vulnerable to bias and confounding. Mendelian randomisation (MR) uses genotype as an instrumental variable to estimate unconfounded causal associations. We conducted a meta-analysis of the observational associations and implemented an MR approach using the smoking-related single nucleotide polymorphism rs16969968 to explore their causal nature.

Setting: 9 British cohorts belonging to the HALCyon collaboration.

Participants: Individual participant data on N=26,692 individuals of European ancestry (N from earliest phase analysed per study) of mean ages 50-79 years were available for inclusion in observational meta-analyses of the primary outcomes.

Primary outcomes: Physical capability, cognitive capability and cognitive decline. The smoking exposures were cigarettes per day, current versus ex-smoker, current versus never smoker and ever versus never smoker.

Results: In observational analyses current and ever smoking were generally associated with poorer physical and cognitive capability. For example, current smokers had a general fluid cognition score which was 0.17 z-score units (95% CI -0.221 to -0.124) lower than ex-smokers in cross-sectional analyses. Current smokers had a walk speed which was 0.25 z-score units lower than never smokers (95% CI -0.338 to -0.170). An MR instrumental variable approach for current versus ex-smoker and number of cigarettes smoked per day produced CIs which neither confirmed nor refuted the observational estimates. The number of genetic associations stratified by smoking status were consistent with type I error.

Conclusions: Our observational analysis supports the hypothesis that smoking is detrimental to physical and cognitive capability. Further studies are needed for a suitably powered MR approach.

Keywords: EPIDEMIOLOGY; GENETICS; GERIATRIC MEDICINE.

Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

PubMed Disclaimer

Figures

**Figure 1**
Meta-analysis of minor allele—cigarettes smoked per day association.

**Figure 2**
Meta-analysis of minor allele—current versus ex-smoker association.

See this image and copyright information in PMC

References

1. Strand BH, Mishra G, Kuh D et al. . Smoking history and physical performance in midlife: results from the British 1946 birth cohort. J Gerontol A Biol Sci Med Sci 2011;66:142–9. 10.1093/gerona/glq199 - DOI - PMC - PubMed
1. Kalmijn S, van Boxtel MP, Verschuren MW et al. . Cigarette smoking and alcohol consumption in relation to cognitive performance in middle age. Am J Epidemiol 2002;156:936–44. 10.1093/aje/kwf135 - DOI - PubMed
1. Cadar D, Pikhart H, Mishra G et al. . The role of lifestyle behaviors on 20-year cognitive decline. J Aging Res 2012;2012:304014 10.1155/2012/304014 - DOI - PMC - PubMed
1. Corley J, Gow AJ, Starr JM et al. . Smoking, childhood IQ, and cognitive function in old age. J Psychosom Res 2012;73:132–8. 10.1016/j.jpsychores.2012.03.006 - DOI - PubMed
1. Galanis DJ, Petrovitch H, Launer LJ et al. . Smoking history in middle age and subsequent cognitive performance in elderly Japanese-American men: the Honolulu-Asia Aging Study. Am J Epidemiol 1997;145:507–15. 10.1093/oxfordjournals.aje.a009138 - DOI - PubMed

Publication types

Actions
Actions
Actions

MeSH terms

Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions
Actions

Save citation to file

Email citation

Add to Collections

Add to My Bibliography

Your saved search

Create a file for external citation management software

Your RSS Feed

Effect of smoking on physical and cognitive capability in later life: a multicohort study using observational and genetic approaches

Affiliations

Effect of smoking on physical and cognitive capability in later life: a multicohort study using observational and genetic approaches

Authors

Affiliations

Abstract

Figures

References

Publication types

MeSH terms

Substances

Grants and funding

LinkOut - more resources

Full Text Sources

Other Literature Sources