Aims Sedentary behaviour (particularly television (TV) viewing) is thought to be a risk factor for cardiovascular disease. We employed a negative control outcome to explore whether the association between TV viewing and heart disease mortality is explained by confounding.
Methods The sample was drawn from the UK Biobank study and comprised 479 658 participants (aged 56.5±8.0 years; 45.7% men) followed up over a mean of 10.4 years. TV viewing was measured from self-report.
Results There were 1437 ischaemic heart disease (IHD) deaths, and 214 accidental deaths (employed as the negative control outcome). TV viewing was related to the following confounding variables: age, smoking, alcohol, diet, obesity, physical inactivity, cardiovascular disease and education. The confounding structures were similar for both outcomes. TV viewing (per hour/d) was associated with IHD (hazard ratio (HR)=1.30, 95% CI, 1.27 to 1.33) and accidental death (HR=1.15, 95% CI, 1.07 to 1.24) in unadjusted models. Associations were attenuated for both outcomes and were considerably converged after adjustment for confounders; IHD (HR=1.09, 95% CI, 1.06 to 1.12) and accidental death (HR=1.06, 95% CI, 0.98 to 1.15).
Conclusion The pattern of results for TV with an implausible outcome mirrored that of IHD, suggesting that observed associations between TV and heart disease are likely to be driven by confounding.
- cardiovascular disease
- cohort studies
- epidemiological methods
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Presented at This research has been conducted using the UK Biobank Resource under Application Number 25 813. The data are publicly available https://www.ukbiobank.ac.uk/. This study was previously presented as an abstract at the ISBNPA 2019 Annual Meeting in Prague.
Contributors MH conceptualised and designed the study, performed analyses, drafted the initial manuscript and approved the final manuscript as submitted. He is the manuscript’s guarantor. ES obtained data, conceptualised and designed the study, provided statistical input and critical revision of the manuscript, and approved the final manuscript as submitted. DD, JC and MD conceptualised and designed the study, provided critical revision of the manuscript and approved the final manuscript as submitted.
Funding DD acknowledges support from Heart Foundation Australia for a Future Leader Fellowship and by the University of Sydney via a SOAR Fellowship. ES acknowledges support from the Health and Medical Research Council (APP1110526) through a Senior Research Fellowship; and support by the University of Sydney via a SOAR Fellowship. MJD is supported by a Career Development Fellowship (APP1141606) from the National Health and Medical Research Council.
Competing interests None declared.
Patient consent for publication Not required.
Ethics approval Ethical approval was provided by the National Health Service, National Research Ethics Service (Ref 11/NW/0382).
Provenance and peer review Not commissioned; externally peer reviewed.