Physical capability in mid-life and survival over 13 years of follow-up: British birth cohort studyBMJ 2014; 348 doi: https://doi.org/10.1136/bmj.g2219 (Published 29 April 2014) Cite this as: BMJ 2014;348:g2219
- Rachel Cooper, senior lecturer and MRC programme leader track1,
- Bjørn Heine Strand, senior scientist2,
- Rebecca Hardy, professor of epidemiology and medical statistics and MRC programme leader1,
- Kushang V Patel, research assistant professor3,
- Diana Kuh, professor of life course epidemiology and MRC unit director1
- 1MRC Unit for Lifelong Health and Ageing at UCL, London WC1B 5JU, UK
- 2Norwegian Institute of Public Health, N-0473 Oslo, Norway
- 3Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, USA
- Correspondence to: R Cooper
- Accepted 10 March 2014
Objectives To examine associations between three commonly used objective measures of physical capability assessed at age 53 and a composite score of these measures and all cause mortality; to investigate whether being unable to perform these tests is associated with mortality.
Design Cohort study.
Setting MRC National Survey of Health and Development in England, Scotland, and Wales.
Participants 1355 men and 1411 women with data on physical capability at age 53 who were linked to the National Health Service (NHS) central register for death notification.
Main outcome measure All cause mortality between ages 53 (1999) and 66 (2012).
Results For each of the three measures of physical capability (grip strength, chair rise speed, and standing balance time) those participants unable to perform the test and those in the lowest performing fifth were found to have higher mortality rates than those in the highest fifth. Adjustment for baseline covariates partially attenuated associations but in fully adjusted models the main associations remained. For example, the fully adjusted hazard ratio of all cause mortality for the lowest compared with the highest fifth of a composite score of physical capability was 3.68 (95% confidence interval 2.03 to 6.68). Those people who could not perform any of the tests had considerably higher rates of death compared with those people able to perform all three tests (8.40, 4.35 to 16.23). When a series of models including different combinations of the measures were compared by using likelihood ratio tests, all three measures of physical capability were found to improve model fit, and a model including all three measures produced the highest estimate of predictive ability (Harrell’s C index 0.71, 95% confidence interval 0.65 to 0.77). There was some evidence that standing balance time was more strongly associated with mortality than the other two measures.
Conclusions Lower levels of physical capability at age 53 and inability to perform capability tests are associated with higher rates of mortality. Even at this relatively young age these measures identify groups of people who are less likely than others to achieve a long and healthy life.
Contributors: All authors contributed to the conception and design of the study; RC and BHS undertook statistical analyses; RC drafted the article and all authors contributed to its critical revision and provided final approval of the version to be published. RC is guarantor. All authors, external and internal, had full access to all of the data (including statistical reports and tables) in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis.
Funding: This work was supported by UK Medical Research Council (programme code MC_UU_12019/4) and the Norwegian Institute of Public Health. The funders of the study had no role in the study design, data collection, data analysis, data interpretation, writing of the report, or the decision to submit the article for publication.
Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.
Ethical approval: Relevant ethical approval was received for this study, with the assessment at 53 approved by the North Thames Multi-Centre research ethics committee. All participants gave informed consent.
Open access: This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 3.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/3.0.
Transparency declaration: RC affirms that the manuscript is an honest, accurate, and transparent account of the study being reported and that no important aspects of the study have been omitted.
Data sharing statement: Bona fide researchers can apply to access the NSHD data via a standard application procedure (further details available at www.nshd.mrc.ac.uk/data.aspx).
This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 3.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/3.0/.