Socio-economic status and mortality in people with type 1 diabetes in Scotland 2006-2015: a retrospective cohort study

Aims: To describe the association between socio-economic status and mortality in a nation-wide cohort of people with type 1 diabetes in Scotland and to compare patterns over time and with the general population.

Methods: A retrospective cohort study was performed using data for people with type 1 diabetes from a population-based register linked to mortality records. Socio-economic status was derived from quintiles of an area-based measure: the Scottish Index of Multiple Deprivation. Sex-specific directly age-standardized mortality rates for each Scottish Index of Multiple Deprivation quintile and rate ratios comparing the most vs least deprived quintile were calculated for two time periods: 2006-2010 and 2011-2015. Data for the population without type 1 diabetes between 2011 and 2015 were available for comparison.

Results: Data for 3802 deaths among 33 547 people with type 1 diabetes were available. The age-standardized mortality rate per 1000 person-years decreased over time (from 2006-2010 to 2011-2015) for men and women with type 1 diabetes: 24.8 to 20.2 and 22.5 to 17.6, respectively. Mortality in populations with and without type 1 diabetes was generally higher for men than women and was inversely associated with socio-economic status. Rate ratios for the most vs least deprived groups increased over time among people with type 1 diabetes (men: 2.49 to 2.81; women: 1.92 to 2.86) and were higher than among populations without type 1 diabetes in 2011-2015 (men: 2.06; women: 1.66).

Conclusions: Socio-economic deprivation was associated with a steeper mortality gradient in people with type 1 diabetes than in the population without type 1 diabetes in Scotland. Age-standardized mortality has decreased over time but socio-economic inequalities may be increasing.