INS and diabetes mellitus: In shared frailty, multivariable Cox regression analyses clustered by practice, foot ulceration (HR 1.48 [95% CI 1.33, 1.66], p < 0.0001) independently predicted long-term mortality after adjustment for age, sex, diabetes type, Townsend index score (HR 1.13 [95% CI 1.10, 1.17], per quintile), smoking status, hypertension, statin treatment, β-blocker treatment, metformin use, HbA1c level (per 10 mmol/mol) and insulin use (Fig. 5).