Declining incidence rates of distal symmetric polyneuropathy in persons with type 1 and type 2 diabetes in Denmark, with indications of distinct patterns in type 1 diabetes.
Objective It is not known if incidence rates for diabetic distal symmetric polyneuropathy (DSPN) are decreasing, as for other diabetic complications. Here, we investigated incidence rates for DSPN in type 1 and type 2 diabetes in a large population-based study.
Research design and Methods In the period 1996 to 2018 19,342 individuals were identified at a Danish tertiary diabetes center. Vibration perception threshold (VPT) was assessed by biothesiometry, repeated throughout the study. Exclusion of prevalent DSPN cases or missing data left 9,473 individuals for analysis of DSPN using a cut-off above 25 V and 2,783 individuals using age-sex-height specific cut-offs. Poisson regression analysis was used to model incidence rates of DSPN for both cut-offs and separately for diabetes types. Covariates were sex, age, diabetes duration and calendar time.
Results Incidence rates of DSPN decreased from 1996 to 2018 e.g., from 4.78 [3.60-6.33] /100 PY to 1.15 [0.91-1.47] /100 PY for 40-year-old men with type 1 diabetes and from 16.54 [11.80-23.18] /100 PY to 8.02 [6.63-9.69] /100 PY for 60-year-old men with type 2 diabetes, when using above 25 V as cut-off.
Analyses using age-sex-height specific cut-off demonstrated similar incidence patterns by calendar time without sex differences. For type 1 diabetes, decreasing incidence rate were seen with higher age.
Conclusion Incidence rates for DSPN are declining in type 1 and type 2 diabetes, possibly due to improved diabetes treatment. This causality remains to be explored. Distinct age-related patterns indicate that the pathophysiology of DSPN may differ between diabetes types.