Socioeconomic indicators of health inequalities and female mortality: a nested cohort study within the United Kingdom Collaborative Trial of Ovarian Cancer Screening (UKCTOCS)
BACKGROUND
Evidence is mounting that area-level socioeconomic indicators are important tools for predicting health outcomes. However, few studies have examined these alongside individual-level education. This nested cohort study within the control arm of the United Kingdom Collaborative Trial of Ovarian Cancer Screening (UKCTOCS) assesses the association of mutually adjusted individual (education) and area-level (Index of Multiple Deprivation-IMD 2007) socioeconomic status indicators and all-cause female mortality.


METHODS
Participants resident in England who had completed both baseline (Wave 1) and follow up (Wave 2) questionnaires were included. Follow-up was through the Health and Social Care Information Centre with deaths censored on 31st December 2012. IMD, education and a range of covariates were explored. Cox regression models adjusted for all covariates were used. Sensitivity analysis using imputation was performed (1) including those with missing data and (2) on the entire cohort who had completed the baseline questionnaire.


RESULTS
Of the 54,539 women resident in England who completed both Wave 1 and Wave 2 questionnaires, 4,510 had missing data. The remaining 50,029 women were included in the primary analysis. Area-level IMD was positively associated with all-cause mortality for the most deprived group compared to the least deprived (HR=1.42, CI=1.14-1.78) after adjusting for all potential confounders. Sensitivity analyses showed similar results with stronger associations in the entire cohort (HR=1.90, CI=1.68-2.16). The less educated an individual, the higher the mortality risk (test for trend p=<0.001). However, the crude effect on mortality of having no formal education compared to college/university education disappeared when adjusted for IMD rank (HR=1.08, CI=0.93-1.26).


CONCLUSION
Women living in more deprived areas continue to have higher mortality even in this less deprived cohort and after adjustment for a range of potential confounders.


TRIAL REGISTRATION
This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN22488978.