Social Deprivation modifies the association between incident foot ulceration and mortality in type 1 and type 2 diabetes: a longitudinal study of a primary care cohort

Aim/hypothesis
Our aim was to determine whether social deprivation in the presence of diabetes is an independent predictor of developing a foot ulcer and separately of mortality.
Methods
This was a primary care based retrospective analysis of 13,995 adults with type 1 (1,344) and type 2 (12,651) diabetes after a median follow-up of 10.5 years.
Demographic, indices of social deprivation and clinical variables were assessed at baseline. The primary outcomes were new foot ulceration (in those without a
previous history of foot ulcers) and all-cause mortality. We used Cox proportional hazard models to describe the association between foot-ulceration, social deprivation and mortality.
Results
The mean age of the population was 69.4 (16, 89) years. The incidence of foot
ulceration was greater in patients with type 2 (8.5%) compared to type 1 diabetes
(5.2%). Occurrence was similar by sex but increased with age and deprivation index. Individuals in the highest quintile of deprivation were 62% more likely to develop a foot ulcer compared to those in the lowest quintile. 2,946 (21.1%) deaths were recorded. The development of a foot ulcer was associated with greater age-sex adjusted mortality rates (25.9% vs. 14.0%) and a 71% (50, 90%) increased risk of mortality. Mortality increased per quintile of deprivation (HR: 13% (8-19%). In a multivariate analysis, increased risk of mortality in patients with a foot ulcer (HR: 1.40 (1.23, 1.60) was amplified by the Townsend deprivation score (14% (10, 18%) increased mortality per quintile) independent of baseline age, sex, diabetes type, smoking status, hypertension, statin, beta-blocker, metformin HbA1c levels and insulin use.
Conclusions/interpretation
This study confirms the high mortality of patients with diabetes related foot ulcers. In addition, socioeconomic disadvantage is an independent effect modifier and contributes to an increased burden of mortality in people with diabetes who develop foot ulceration. In the light of this, modelling of foot ulceration risk needs to take account of socioeconomic disadvantage, as diabetes service configuration is orientated for the next 5-10 years.