Abstract
UK Biobank is a population-based cohort of 500,000 participants recruited between 2006 and 2010. Approximately 9.2 million individuals aged 40-69 years who lived within 25 miles of the 22 assessment centres in England, Wales and Scotland were invited, and 5.4% participated in the baseline assessment. The representativeness of the UK Biobank cohort was investigated by comparing demographic characteristics between non-responders and responders. Sociodemographic, physical, lifestyle and health-related characteristics of the cohort were compared with nationally representative data sources. UK Biobank participants were more likely to be older, women and to live in less socioeconomically deprived areas than non-participants. Compared with the general population, participants were less likely to be obese, smoke, drink alcohol on a daily basis and had fewer self-reported health outcomes. Rates of all-cause mortality and total cancer incidence (at age 70-74 years) were 46.2% and 11.8% lower in men, and 55.5% and 18.1% lower in women, respectively, than the general population of the same age. UK Biobank is not representative of the sampling population, with evidence of a ‘healthy volunteer’ selection bias. Nonetheless, the valid assessment of exposure-disease relationships may be widely generalizable and does not require participants to be representative of the population at large.
