Author Affiliations: Department of Epidemiology and Public Health, University College London, London, England.
Measures of self-rated health are powerful predictors of objective health outcomes,1 although these measures generally do not differentiate between specific domains of functional health. This information is critical to inform future interventions for prevention. In particular, the association between self-reported physical functional health and future risk of cardiovascular disease (CVD) in the general population has received limited attention.2,3 In the present study we used the Physical Component Summary (PCS) score from the 12-Item Short-Form Survey Instrument (SF-12) to examine associations with incident CVD events and all-cause mortality in a sample of adults without overt CVD from the general population.
The sample included 4780 adults 35 years and older (mean [SD] age, 52.2 [4.5] years; 56.4% female) measured in the 2003 Scottish Health Survey; 77% of eligible households took part in the survey. Participants gave full informed consent to participate in the study, and ethical approval was obtained from the London Research Ethics Council. We linked these data to records of hospital admissions and mortality with follow-up until December 2007; thus, the analyses were based on a prospective cohort design, as described previously.4 The main exclusion criterion for the present analysis was a history of clinically confirmed CVD, which was identified from retrospective patient hospital records. Survey interviewers visited eligible households and collected data on demographics and lifestyle (eg, smoking, alcohol, physical activity) variables, measured height and weight, and administered the SF-12 that assesses 8 attributes of functional health status and has demonstrated strong validity and reliability.5 We used one of the SF-12 subscales (PCS) as an indicator of physical functional health; the raw scores are transformed into a scale of 0 to 100, representing poor to good health, respectively. On a separate visit, nurses collected clinical data (medical history, medication, and 3 seated blood pressure readings).
Compared with those in the top quarter, participants in the lowest quarter of physical function were older (62.2 vs 49.4 years; P < .001) and more likely to smoke (26.2% vs 21.1%; P < .001), be in the lowest tertile of physical activity (62.4% vs 27.1%; P < .001), come from lower social strata (IV/V part skilled/unskilled; 27.6% vs 20.8%; P < .001), be obese (30.7% vs 13.7%; P < .001), and have hypertension (43.8% vs 15.8%; P < .001). Over a mean 4.3-year follow up, there were 297 incident CVD events (hospital admissions and deaths combined) and 189 total deaths. In Cox proportional hazards models, there was a linear association between PCS score and risk of CVD (P value for trend, <.001) (Table), with none of the 95% confidence intervals (CIs) containing unity. Participants in the highest quarter of physical function had a 60% (95% CI, 38%-74%) reduced risk after adjustment for potential confounders. Similar associations were observed for all-cause mortality. Adjusting for a wide range of potential covariates resulted in only modest attenuation of risk estimates. When we limited the analyses to younger participants (younger than 60 years, n = 3232) we observed similar associations for CVD (hazard ratio in the highest quartile, 0.26; 95% CI, 0.13-0.54).
In this geographically representative cohort of healthy individuals, we observed a robust, stepwise association between physical functional health, as indicated by the PCS, and incident CVD events and all-cause mortality. Although physical function was strongly associated with a number of modifiable risk factors, such as physical activity, the associations of PCS and CVD appeared to be largely independent of these factors. These findings support the few previous studies in this area2,3 and underline the importance of physical function as a risk marker for future health. It has been suggested that measures of self-reported health status, such as the SF-12, capture the subclinical stage of a condition before it can be detected by objective clinical measures. Indeed, we recently demonstrated an association between gait speed on a short-distance walking test and subclinical coronary atherosclerosis in seemingly healthy individuals.6 In conclusion, the present findings suggest that self-rated physical function is a robust predictor of future CVD risk and may, therefore, be usefully incorporated into a standard physician's medical examination.
Correspondence: Dr Hamer, Department of Epidemiology and Public Health, 1-19 Torrington Pl, University College London, London WC1E 6BT, England (email@example.com).
Author Contributions: Dr Hamer had full access to the data and takes responsibility for the integrity of the data and accuracy of the data analyses. Study concept and design: Hamer, Kivimaki, and Stamatakis. Acquisition of data: Stamatakis. Analysis and interpretation of data: Hamer and Batty. Drafting of the manuscript: Hamer and Stamatakis. Critical revision of the manuscript for important intellectual content: Hamer, Batty, Kivimaki, and Stamatakis. Statistical analysis: Hamer, Kivimaki, and Stamatakis. Obtained funding: Kivimaki.
Financial Disclosure: None reported.
Funding/Support: The Scottish Health Survey is funded by the Scottish Executive. Dr Hamer is supported by the British Heart Foundation (RG 05/006); Dr Batty is a Wellcome Trust Career Development Fellow (WBS U.1300.00.006.00012.01). Dr Kivimaki is supported by the National Heart, Lung, and Blood Institute (R01HL036310) and the National Institute on Aging (R01AG034454), National Institutes of Health (United States), the BUPA Foundation (United Kingdom), and the Academy of Finland (Finland). Dr Stamatakis is supported by the National Institute of Health Research.
Role of the Sponsors: The funders played no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, or approval of the manuscript.
Disclaimer: The views expressed in this article are those of the authors and not necessarily of the funding bodies.
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