Decreasing national trends in diabetic complications hide regional differences: a prospective population-based study using health care registers in Finland

Objectives. To examine whether possibilities to improve care among patients with diabetes are reflected in the numbers of cardiovascular complications at national and regional level in Finland. Methods. The study population included all patients with diabetes in Finland since 1964. The incidences of first acute coronary syndrome, ischemic stroke and lower limb amputation were examined for the period from 2010 to 2017. The age- and sex-standardised incidence rates were calculated for the first events. Adjusted Poisson regression mixed models were used to calculate average annual trends and assess regional variation of incidences during the periods 2010 to 2013 and 2014 to 2017 in the university hospital districts (UHDs) and hospital districts (HDs). Results. The nationwide incidence of first acute coronary syndrome decreased among patients with diabetes by 2.7% (95% confidence interval 2.3%; 3.0%), ischemic stroke by 2.0% (1.5%; 2.4%) and major lower limb amputation by 4.6% (3.1%; 5.9%) annually. The sexes differed only in the decrease in acute coronary events. The annual decrease among males was 2.1% (1.6%; 2.6%) and among females was 3.4% (2.8%; 4.0%) (p = .001). Marked variation was observed among UHDs and HDs in the incidences of cardiovascular events and lower limb amputations in patients with diabetes. The variation in annual trends of diabetic complications was most pronounced in acute coronary syndrome among UHDs with an estimated variance of 0.0006 (p = .034). Conclusions. The decrease in the incidence of first cardiovascular events among patients with diabetes continued from 2010 to 2017 in Finland. However, the declining national incidence rates hide regional differences which should be a target for improvement.