Impaired glucose metabolism in hypertensive patients with/without the metabolic syndrome

Background: In hypertension clinics, screening patients for the metabolic syndrome (MetS) is common practice, while performing the cumbersome oral glucose tolerance test (OGTT) is not. How large is the underestimation of diabetes and prediabetes that ensues is unknown.

Methods: We recruited N=1397 patients with essential arterial hypertension who underwent a 75-g OGTT and were classified as normally glucotolerant (NGT) or having impaired glucose metabolism (IGM), and as affected or not by MetS (ATPIII criteria). The agreement between the OGTT and the ATPIII criteria in attributing a high cardiovascular risk was estimated by matching the categories of MetS and no-MetS with NGT and IGM.

Results: n=677/1397 patients (48%) satisfied criteria for MetS, while n=757/1397 (54%) had an IGM. MetS and IGM were both present in n=512/1397 patients (36.6%), and both absent in n=475/1397 (34%). Further n=410/1397 patients (29%) were discordant for the two conditions: n=165/410 (40%) had the MetS but were NGT, and n=245/410 (60%) had IGM but no MetS. Among IGM patients, n=168/757 (22%; of which 45 had no MetS) received a new diagnosis of diabetes based on OGTT criteria. Among all discordant patients, those with IGM and no MetS were more commonly males (p<0.001), and had older age (p<0.001) and lower body mass index (p<0.05).

Conclusions: Among patients with hypertension, the estimate of the prevalence of diabetes and prediabetes, hence of the global cardiovascular risk, can be seriously flawed unless an OGTT is performed. Our results support a wider use of the OGTT in the management of hypertension.