Masked Hypertension and Diabetes

In patients with diabetes, control of blood pressure (BP) is as important as glycemic control in preventing cardiovascular disease. In hypertension and diabetes guidelines, the evaluation of BP is limited to clinic BP; out-of-office BP monitoring is not recommended for diabetic patients. Recently, an accumulation of evidence has shown that out-of-office BP monitoring is useful for risk stratification in diabetes. Especially, masked hypertension, defined as normal clinic BP but high BP in the ambulatory condition, is a big clinical problem. Masked hypertension in diabetes is associated with advanced target organ damage, such as silent brain damage, cardiac hypertrophy, renal damage, and atherosclerosis. Cardiovascular autonomic neuropathy (CAN) has been reported to be associated with cardiovascular complications, but CAN in the early stage is difficult to detect. CAN could be a cause of increased fluctuation of BP and abnormal circadian rhythm of BP. For example, masked nocturnal hypertension, defined as normal BP in the daytime but high BP at night, is difficult to diagnose, and is also associated with advanced target organ damage. In conclusion, masked hypertension exists also in substantial proportion of diabetic patients and is associated with advanced target organ damage. The cardiovascular prognosis of masked hypertension in diabetes will be clarified in the near future. The primary mechanism underlying masked hypertension or masked nocturnal hypertension in diabetes would be the presence of CAN, which is also an independent predictor for cardiovascular prognosis. Further study is needed to test the cardiovascular prognosis of masked hypertension in diabetes in order to clarify whether or not out-of-office BP measurement is really necessary in the management of BP.