Foot Ulcer and Risk of Lower Limb Amputation or Death in People With Diabetes: A National Population-Based Retrospective Cohort Study

Abstract

OBJECTIVE To describe incidence of foot ulceration and amputation-free survival associated with foot ulceration status in a national population-based cohort study of people with diabetes. RESEARCH DESIGN AND METHODS The study population included 233,459 people with diabetes who were alive in Scotland on 1 January 2012 identified from the national population-based register (national prevalence 4.9%). Characteristics of patients identified from linked hospital and mortality records during follow-up to the end of November 2017 were compared by outcome. Cox regression was used to assess the association between history of foot ulcer and amputation-free survival. RESULTS The population included 23,395 people with type 1 diabetes and 210,064 people with type 2 diabetes. In total there were 13,093 (5.6%) people who had a previous foot ulceration, 9,023 people who developed a first ulcer, 48,995 who died, and 2,866 who underwent minor or major amputation during follow-up. Overall incidence of first-time foot ulcers was 7.8 per 1,000 person-years (95% CI7.6–7.9) and 11.2 (11.0–11.4) for any ulcer. Risk factors for reduced amputation-free survival included social deprivation, mental illness, and being underweight in addition to conventional cardiovascular risk factors. Adjusted hazard ratios (95% CI) were 2.09 (1.89–2.31) for type 1 diabetes and 1.65 (1.60–1.70) for type 2 diabetes. CONCLUSIONS The overall incidence of foot ulceration in a population-based study of people with diabetes was 11.2 per 1,000 person-years. Foot ulceration is associated with lower amputation-free survival rate, a potential measure of effectiveness of care among people with diabetes. Mental illness and social deprivation are also highlighted as risk factors.