• Tom C Russ, John M Starr, Emmanuel Stamatakis, Mika Kivimäki, and G David Batty.
• Alzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, UK Scottish Dementia Clinical Research Network, NHS Scotland, UK Centre for Cognitive Ageing & Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK Division of Psychiatry, University of Edinburgh, Edinburgh, UK.
• J Epidemiol Community Health. 2015 Jun 1; 69 (6): 550-6.

BackgroundIn addition to being associated with all-cause mortality and cardiovascular disease mortality, lung function has been linked with dementia. However, existing studies typically provide imprecise estimates due to small numbers of outcome events and are based on unrepresentative samples of the general population.MethodsIndividual participant meta-analysis of six cohort studies from the Health Survey for England and the Scottish Health Survey (total N=54 671). Dementia-related mortality was identified by mention of dementia on any part of the death certificate (mean follow-up 11.7 years). Study-specific Cox proportional hazard models of the association between lung function and dementia-related death were pooled using random effect meta-analysis to produce overall results.ResultsThere was a dose-response association between poorer lung function and a higher risk of dementia-related death (age- and sex-adjusted HR compared to highest quartile of forced expiratory volume in 1 s (FEV1), 95% CI: second quartile 1.32, 0.99 to 1.76; third quartile 1.78, 1.30 to 2.43; fourth (lowest) quartile 2.74, 1.73 to 4.32). There was no significant heterogeneity in study-specific estimates (I(2)=0%). Controlling for height, socioeconomic status, smoking and general health attenuated but did not remove the association (second quartile 1.15, 0.82 to 1.62; third quartile 1.37, 0.96 to 1.94; fourth quartile 2.09, 1.17 to 3.71). Results for forced vital capacity and peak flow were similar.ConclusionsIn these general population samples, the relation between three measures of lung function and dementia death followed a dose-response gradient. Being in the bottom quartile of lung function was associated with a doubling of the risk.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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