Increased risk of non-insulin-dependent diabetes mellitus in elderly hypertensive subjects

BACKGROUND: In several studies hypertension has been shown to be associated with an increased incidence of non-insulin-dependent diabetes mellitus (NIDDM). This may be due to hypertension itself or to the deleterious effects of some antihypertensive agents on glucose tolerance and insulin sensitivity. METHODS: We examined the 3.5-year incidence of diabetes mellitus in relation to hypertension and antihypertensive medication in a population-based study of elderly subjects (n = 805) aged 65-74 years in Kuopio, Finland. RESULTS: Of the subjects studied, 60% had hypertension at baseline and 50% of the hypertensive subjects were on drug therapy at baseline. Hypertensive subjects had a significantly higher incidence of NIDDM than non-hypertensive subjects. However, after adjustment for age, body mass index, waist: hip ratio, sex, and fasting glucose and insulin levels, the increased risk of NIDDM in hypertensive subjects was no longer statistically significant. Subjects with high blood pressure (> or = 160/95 mmHg) at the baseline examination who were not taking beta-blockers or diuretic medication had a 1.56-fold increased risk of developing NIDDM, whereas subjects with hypertension who were taking those agents had a 1.88-fold risk of developing NIDDM compared with subjects with normal blood pressure. The risk of developing NIDDM was accompanied by elevated fasting insulin levels. After adjustment for age, sex, body mass index, waist:hip ratio, and fasting glucose and insulin levels, hypertensive subjects taking diuretics or beta-blockers, or both, still had a 1.56-fold increased risk of developing NIDDM relative to normotensive subjects. Hypertensive subjects taking diuretics or beta-blockers, or both, had a significantly higher incidence of NIDDM than hypertensive subjects not on pharmacological therapy. However, after adjustment for 2-h glucose and insulin concentrations, the incidence of NIDDM did not differ between the hypertensive subjects. CONCLUSION: The data presented suggest that the increased risk of NIDDM in hypertensive subjects taking beta-blockers or diuretics, or both, is explained at least partly by metabolic disturbances related to drug therapy.