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Prehypertension a Risk Factor for Type 2 Diabetes

Whether or not blood pressure categories below 140/90 mmHg are associated with incident Type 2 diabetes or cardiovascular disease is subject to debate….

Currently, a blood pressure of 120–139/80–89 mmHg is recognized as prehypertension.

This article evaluates the association of prehypertension with incident Type 2 diabetes in the San Antonio Heart study. The authors found that prehypertension in the entire cohort was not related to incident Type 2 diabetes in fully adjusted analyses, but that a blood pressure of 130-139/85-89 mmHg was related to incident diabetes. These results, and conclusions of other studies, suggest that the prehypertension category should be divided for diabetes risk assessment.

The study by Mullican et al. was a retrospective analysis to determine if prehypertension is a risk factor for developing Type 2 diabetes. Data were obtained from the San Antonio Heart Study, which is a longitudinal study on cardiovascular disease and Type 2 diabetes. Study participants were Mexican-Americans and non-Hispanic white individuals, aged 25-65 years who reside in San Antonio (TX, USA). There were 2,767 participants with a median follow-up of 7.8 years who were eligible for analysis after excluding those with pre-existing diabetes or hypertension, and those lost in follow-up. JNC 7 criteria were used to classify blood pressure as normal, prehypertension or hypertension, and American Diabetes Association guidelines were used to define plasma glucose levels for diabetes. A multivariate logistic-regression model was used to determine the association of prehypertension with the future development of diabetes.

The baseline prevalence of prehypertension was 31.3%. Prehypertension was associated with male gender, Mexican-American ethnic­ity, higher BMI, triglycerides and measures indi­cating impaired glucose tolerance and insulin resistance. Systolic blood pressure was positively associated with BMI, waist circumference, trig­lycerides and measures indicating impaired glucose tolerance and insulin resistance. A total of 5.6 and 12.4% of subjects who were normal and prehypertensive, respectively, developed diabe­tes during the study period. The odds ratio for incident diabetes was 2.21 for prehypertensive subjects versus those with normal blood pressure when controlling for age, gender and ethnicity. However, when BMI and risk factors for diabetes (measures of impaired glu­cose tolerance, insulin resistance and family history of diabetes) were also adjusted for, the association was not significant. There was a significant relationship for blood pressures ranging from 130-139/85-89 mmHg when the same variables were used in the regression model.

Mullican et al. showed that a blood pressure of 130-139/85-89 mmHg was associated with incident diabetes in the San Antonio Heart Study. Along with three out of six studies of cardiovascular disease, this study points to the difficulty of using the prehypertension category as defined in the JNC 7 in determining diabetes risk, and suggests the JNC 6 categories illuminate important differences in patient populations. This recommendation also needs to be viewed from the standpoint of the treatment of individuals having diabetes and prehyperten­sion. Should these individuals be treated as though they have hypertension even if their blood pressure is 120/80 mmHg? Would the JNC 6 categories be more useful? The evidence appears to be firmly mixed with respect to incident diabetes and cardiovascular disease events.

In conclusion, Prehypertension is presently recognized as a risk factor for cardiovascular disease. Prehypertension was not found to be related to incident Type 2 diabetes in fully adjusted analyses of the San Antonio Heart study. A blood pressure of 130–139/85–89 mmHg was found to be associated with incident diabetes, and may be a more meaningful category for diabetes risk assessment.

Mullican DR, Lorenzo C, Haffner SM. Is prehypertension a risk factor for the development of Type 2 diabetes? Diabetes Care 32(10), 1870–1872 (2009).