Background The linkage of data from representative population surveys to routine administrative data sources is a powerful and efficient way of turning a cross-sectional study into a longitudinal one that obviates responder burden and bias, and simplifies issues of temporality. However, linkage depends on individual consent and while the factors influencing survey response are well described much less is known about factors influencing consent for record linkage. The aims of this study were to examine the demographic, socioeconomic, health and lifestyle factors associated with consent to linkage to personal medical records within wave 1 of Understanding Society. Wave 1 was conducted between January 2009 and December 2010 and had an overall household response rate of 57.6% and an individual response rate of 81.8% (all general population sample estimates).

Methods All survey respondents were provided with an information leaflet about the linkage of health data and were asked to read and sign a consent form (main outcome). The analysis herein included individuals aged 16-74 years (n = 47,367). After removing proxy respondents and those with missing data the final dataset included 43,709 individuals. Univariate and multivariate multi-level logistic regression models were used to investigate demographic, socioeconomic, health and lifestyle factors associated with consent to linkage.

Results Overall, 68.6% (30,003/43,709) of respondents agreed to data linkage. Consent to linkage was lower at older ages, but there was no variation according to sex; those who were married/divorced were slightly more likely to consent (Adjusted Odds Ratio (AOR) 1.13 [95% CI 1.06, 1.25]) as were those of white ethnicity (1.61 [1.52, 1.71]). Individuals with a limiting and long term illness had slightly higher consent rates (1.11 [1.06, 1.16]). Regional variation in consent emerged, with respondents from Scotland 17% more likely, than those from England, to consent to linkage (1.17 [1.07, 1.29]) with individuals from Northern Ireland 44% less likely to consent (0.56 [0.50, 0.63]).

Conclusion There are important differences in the factors influencing response to an initial survey and subsequent consent to data linkage. An unexpected finding was the regional variation in consent rates, particularly the higher uptake in Scotland. More research is needed to understand if these variations reflect general mistrust, lack of understanding or factors related to interviewer perception.