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White-coat hypertension not benign for patients with type 2 diabetes, study suggests

Tuesday, October 14 2008 | Comments

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What's This? White-coat hypertension may increase the risk of microvascular complications for patients with type 2 diabetes, according to a preliminary study.

Researchers in Brazil conducted a cross-sectional study, comparing individuals with normal blood pressure (BP) to those with white-coat hypertension--that is, patients with normal BP values during ambulatory monitoring (ABPM) but elevated BP values in a physician's office.

Typically, clinicians consider such patients to have a low-risk profile for vascular complications, the researchers noted, even though previous studies suggest patients with type 1 diabetes and white-coat hypertension are at increased risk for sustained hypertension and microalbuminuria. In the current study, the investigators sought to characterize patients with type 2 diabetes and white-coat hypertension and to determine its effects on chronic diabetes complications.

The researchers selected participants from a cohort of individuals with type 2 diabetes (n=319). Among these individuals, 46 had white-coat hypertension, defined as an office BP >=140/90 mm Hg and a daytime ABPM <135/85 mm Hg, while 117 met criteria for normal BP (office BP <140/90 mm Hg and ABPM <135/85 mm Hg).

These 2 groups were similar in age, duration of diabetes, anthropometric measures, renal function, glycemic control, and lipid profile, but individuals with white-coat hypertension had higher mean values for systolic ABPM (24-hr, P=.01; daytime, P=.01; nighttime, P=.07), pulse pressure (24-hr, P=.01; daytime, P=.05; nighttime, P=.17), and BP loads (24-hour systolic BP load; P=01; 24-hour diastolic BP load, P=.03; daytime systolic BP load, P=.01; daytime diastolic BP load, P=04; nighttime systolic BP load, P=.02; nighttime diastolic BP load, P=.06).

In a subgroup of individuals who completed exercise testing (n=56; 18 with white-coat hypertension), individuals with white-coat hypertension also had higher maximum BP levels (systolic, P=.002; diastolic, P=.02) even though the 2 groups demonstrated equivalent levels of effort during the test.

In general, patients with white-coat hypertension had higher urinary albumin excretion rates (UAER) as compared with normotensive patients (median, 15.5 mcg/min vs 7.4 mcg/min; P=.01). White-coat hypertension was also associated with a nearly 5-fold increase in the odds of having macroalbuminuria (OR, 4.9; 95% CI, 1.3-18.7; P=.01). This increased risk was sustained after adjusting for diabetes duration and hemoglobin A1C (OR 2.0; 95% CI, 1.3-3.2; P=.02). White-coat hypertension was not associated with an increased risk of having microalbuminuria.

Diabetic retinopathy was also more common among patients with white-coat hypertension as compared with normotensive patients (57.9% vs 34.4%; P=.01). Furthermore, white-coat hypertension was associated with a significantly increased risk of both nonproliferative and proliferative diabetic retinopathy (adjusted OR, 2.7, 95% CI, 1.2-6.6; P=.02 for any degree of diabetic retinopathy) after adjustment for diabetes duration and hemoglobin A1C.

The investigators also noted that the "white-coat effect," or the difference between mean office systolic BP and mean systolic ABPM, was associated with the UAER even after adjusting for potential confounders (P=.03), and that individuals with proliferative diabetic retinopathy had a significantly greater white-coat effect than did those with nonproliferative diabetic retinopathy or no diabetic retinopathy (P=.04).

"These findings indicate that white-coat hypertension is not a benign situation in type 2 diabetes patients, most likely representing an intermediary phenotype between normotension and hypertension," the authors concluded.

These findings were published online September 3 ahead of print in Diabetes Care by Kramer CK, et al.

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