Pulmonary function as a risk factor for dementia death: an individual participant meta-analysis of six UK general population cohort studies
- 1Alzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, UK
- 2Scottish Dementia Clinical Research Network, NHS Scotland, UK
- 3Centre for Cognitive Ageing & Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK
- 4Division of Psychiatry, University of Edinburgh, Edinburgh, UK
- 5Department of Epidemiology and Public Health, University College, London, UK
- 6Charles Perkins Centre, University of Sydney, Australia
- 7Exercise and Sport Sciences, Faculty of Health Sciences, University of Sydney, Australia
- Correspondence to Dr Tom C Russ, Division of Psychiatry, University of Edinburgh, Kennedy Tower, Royal Edinburgh Hospital, Morningside Terrace, Edinburgh EH10 5HF, UK;
- Received 16 September 2014
- Revised 16 December 2014
- Accepted 30 December 2014
- Published Online First 17 February 2015
Background In 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.
Methods Individual 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.
Results There 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 (I2=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.
Conclusions In 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.