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Impact of resurvey non-response on the associations between baseline risk factors and cardiovascular disease mortality: prospective cohort study
  1. G D Batty1,2,
  2. C R Gale3
  1. 1
    Medical Research Council Social and Public Health Sciences Unit, Glasgow, UK
  2. 2
    The George Institute for International Health, Sydney, Australia
  3. 3
    Medical Research Council Epidemiology Resource Centre, Southampton, UK
  1. Correspondence to Dr G D Batty, MRC Social and Public Health Sciences Unit, University of Glasgow, 4 Lilybank Gardens, Glasgow G12 8RZ, UK; david-b{at}sphsu.mrc.ac.uk

Abstract

Background: Selection bias in observational epidemiology—the notion that people who participate in a study are fundamentally different from those who do not—is a perennial concern. In cohort studies, a potentially important but little investigated manifestation of selection bias is the distortion of the exposure–disease relationship according to participation status.

Methods: Seven years after the original UK Health and Lifestyle Survey (HALS1; N = 6484), attempts were made to resurvey participants (HALS2). The baseline characteristics, mortality experience following the completion of HALS2 and, finally, the baseline risk factor–cardiovascular disease (CVD) mortality gradients in HALS2 non-participants (N = 1894) and participants (N = 4590) were compared.

Results: Resurvey non-participants, based on data from HALS1, were younger, were of lower social class and had a lower prevalence of hypertension or self-reported limiting long-standing illness, but a higher prevalence of psychological distress (p⩽0.027). The risk of death from future CVD was significantly higher in those baseline study members who did not participate in HALS2. However, the magnitude of the association between a series of risk factors and CVD mortality was essentially the same in the HALS2 non-participants and participants (p value for interaction⩾0.108).

Conclusion: In the present cohort study, non-response at resurvey did not bias the observed associations between baseline risk factors and later CVD mortality. Future studies should also examine the impact of non-response to baseline surveys on these relationships.

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Footnotes

  • Funding The Medical Research Council (MRC) Social and Public Health Sciences Unit receives funding from the MRC and the Chief Scientist Office at the Scottish Government Health Directorates. G-DB is a Wellcome Trust Fellow (WBS U.1300.00.006.00012.01). The MRC supports CG.

  • Competing interests None.

  • Ethics approval Approval was obtained from various Local Research Ethics Committees across the UK.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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