title: Assessment of Non-Response Bias in Estimates of Alcohol Consumption: Applying the Continuum of Resistance Model in a General Population Survey in England.
abstract: BACKGROUND
  Previous studies have shown heavier drinkers are less likely to respond to surveys and require extended efforts to recruit. This study applies the continuum of resistance model to explore how survey estimates of alcohol consumption may be affected by non-response bias in three consecutive years of a general population survey in England.
  
  
  METHODS
  Using the Health Survey for England (HSE) survey years 2011-13, number of contact attempts (1-6 and 7+) were explored by socio-demographic and drinking characteristics. The odds of drinking more than various thresholds were modelled using logistic regression. Assuming that non-participants were similar to those who were difficult to contact (the continuum of resistance model), the effect of non-response on measures of drinking was investigated.
  
  
  RESULTS
  In the fully-adjusted regression model, women who required 7+ calls were significantly more likely to drink more than the UK Government's recommended daily limit (OR 1.19, 95% CI 1.06-1.33, P = 0.003) and to engage in heavy episodic drinking (OR 1.23, 95% CI 1.07-1.42, P = 0.004), however this was not significant in men in the fully-adjusted model. When the continuum of resistance model was applied, there was an increase in average weekly alcohol consumption of 1.8 units among men (a 12.6% relative increase), and an increase of 1.5 units among women (a 20.5% relative increase). There was also an increase in the prevalence of heavy episodic drinking of 2.5% among men (an 12.0% relative increase) and of 2.0% among women (a 15.8% relative increase), although other measures of drinking were less affected.
  
  
  CONCLUSIONS
  Overall alcohol consumption and the prevalence of heavy episodic drinking were higher among HSE participants who required more extended efforts to contact. The continuum of resistance model suggests non-response bias does affect survey estimates of alcohol consumption.
authors.affiliation: National Addiction Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, United Kingdom.
authors.forename: Sadie
authors.identifier: http://orcid.org/0000-0003-3492-6402
authors.initials: S
authors.lastname: Boniface
authors.affiliation: Research Department of Epidemiology & Public Health, University College London, London, United Kingdom.
authors.forename: Shaun
authors.initials: S
authors.lastname: Scholes
authors.affiliation: Research Department of Epidemiology & Public Health, University College London, London, United Kingdom.
authors.forename: Nicola
authors.initials: N
authors.lastname: Shelton
authors.affiliation: Department of Preventive and Social Medicine, University of Otago, Dunedin, New Zealand.
authors.forename: Jennie
authors.initials: J
authors.lastname: Connor
mesh_terms: D000293:Adolescent; D000328:Adult; D000428:Alcohol Drinking / Q000453:epidemiology*; D015982:Bias; D016001:Confidence Intervals; D003710:Demography; D004739:England / Q000453:epidemiology; D005260:Female; D017408:Guidelines as Topic; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D016017:Odds Ratio; D055815:Young Adult