Fasting Glucose Levels and Incident Diabetes Mellitus in Older Nondiabetic Adults Randomized to Receive 3 Different Classes of Antihypertensive Treatment

BACKGROUND: Elevated blood glucose levels are reported with thiazide-type diuretic treatment of hypertension. The significance of this finding is uncertain. Our objectives were to compare the effect of first-step antihypertensive drug therapy with thiazide-type diuretic, calcium-channel blocker, or angiotensin-converting enzyme inhibitor on fasting glucose (FG) levels and to determine cardiovascular and renal disease risks associated with elevated FG levels and incident diabetes mellitus (DM) in 3 treatment groups. METHODS: We performed post hoc subgroup analyses from the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT) among nondiabetic participants who were randomized to receive treatment with chlorthalidone (n = 8419), amlodipine (n = 4958), or lisinopril (n = 5034) and observed for a mean of 4.9 years. RESULTS: Mean FG levels increased during follow-up in all treatment groups. At year 2, those randomized to the chlorthalidone group had the greatest increase (+8.5 mg/dL 0.47 mmol/L vs +5.5 mg/dL 0.31 mmol/L for amlodipine and +3.5 mg/dL 0.19 mmol/L for lisinopril). The odds ratios for developing DM with lisinopril (0.55 95% confidence interval, 0.43-0.70) or amlodipine (0.73 95% confidence interval, 0.58-0.91) vs chlorthalidone at 2 years were significantly lower than 1.0 (P<.01). There was no significant association of FG level change at 2 years with subsequent coronary heart disease, stroke, cardiovascular disease, total mortality, or end-stage renal disease. There was no significant association of incident DM at 2 years with clinical outcomes, except for coronary heart disease (risk ratio, 1.64; P = .006), but the risk ratio was lower and nonsignificant in the chlorthalidone group (risk ratio, 1.46; P = .14). CONCLUSIONS: Fasting glucose levels increase in older adults with hypertension regardless of treatment type. For those taking chlorthalidone vs other medications, the risk of developing FG levels higher than 125 mg/dL (6.9 mmol/L) is modestly greater, but there is no conclusive or consistent evidence that this diuretic-associated increase in DM risk increases the risk of clinical events.