Incidence of distal symmetric (sensory) neuropathy in NIDDM - The San Luis Valley Diabetes Study

OBJECTIVE - To determine the incidence and risk factors for distal symmetric sensory neuropathy (DSN) in people with NIDDM. RESEARCH DESIGN AND METHODS - Prospective follow-up was conducted from 1988 to 1992 on 231 people free of DSN during the baseline period 1984-1988 (mean follow-up, 4.7 years). Subjects with incident DSN (n = 66) were defined by any two of three criteria: 1) bilateral paresthesia in legs or feet; 2) bilateral decreased or absent ankle reflexes; and/or 3) bilateral decreased or absent cold temperature discrimination in feet. Of all 66 cases, 42 had one positive follow-up visit; 14 cases had 2 positive follow-up visits. RESULTS - The overall incidence rate of DSN was 6.1 per 100 person-years (95% CI, 4.7-7.8). The rate for Hispanics (n = 164) and non-Hispanic whites (n = 67), adjusted for age, sex, and NIDDM duration, was 5.3 per 100 person-years (95% CI, 3.9-7.0) and 5.0 per 100 person-years (95% CI, 2.8-8.1), respectively. Adjusting for age and sex, higher glycohemoglobin level and lower C-peptide secretion were associated with increased DSN but were no longer predictive after accounting for duration of diabetes. Logistic regression models found significantly increased risk of DSN for insulin treatment, current smoking, and history of myocardial infarction. Duration was related to DSN incidence until insulin treatment was included. Other risk factors, including height, weight, family history of diabetes, peripheral vascular disease, hypertension, urinary albumin, protein:creatinine ratio, retinopathy, and alcohol use, were not significantly related to incident DSN. CONCLUSIONS - Hispanic and non-Hispanic whites with NIDDM have similar risks of DSN. Current cigarette smoking and a history of myocardial infarction may represent independent risk factors for DSN in addition to glycemic control.