With commentary by lead study author Ramón C. Hermida, PhD, director of the Bioengineering & Chronobiology Laboratory at University of Vigo, Spain
“Taking hypertension medications at bedtime, instead of upon awakening in the morning, improves sleep-time blood pressure, reduces cardiovascular morbidity and mortality and markedly reduces the risk of developing diabetes,” said lead author of both studies, Ramón C. Hermida, PhD, director of the Bioengineering & Chronobiology Laboratory at University of Vigo, Spain.
In their study of 2,656 men and women without type 2 diabetes (average age 50.6), researchers discovered that by the end of the 5.9 year median follow-up, 190 people developed type 2 diabetes. The most important predictor: high systolic blood pressure while patents were sleeping.
And in their subsequent study of 2,012 hypertensive people without diabetes, the researchers found that subjects randomly assigned to take blood pressure medications at night not only had lower sleep-time systolic blood pressure, but were half as likely to develop type 2 diabetes as those who took blood pressure medications in the morning (4.8% compared with 12.1%).
Blood pressure normally decreases during the night by 10% or more. But in those with diabetes, blood pressure is more likely to remain high during sleep. This pattern, known as non-dipping, which can also occur in those with hypertension, is linked with glucose intolerance and other metabolic conditions. Growing evidence suggests that non-dippers face a variety of increased cardiovascular risks.
Indeed, diabetes and hypertension often go hand in hand. Hypertension occurs in approximately 70% of people with type 2 diabetes in the U.S. and is about twice as common in those with diabetes as in those without. The two disorders have common etiologies and disease mechanisms including obesity, inflammation, oxidative stress and insulin resistance.
And while hypertension itself is considered a risk factor for type 2 diabetes, research has shown that some blood-pressure medications including diuretics and beta-blockers, especially when taken without other types of blood pressure drugs, may actually promote type 2 diabetes, especially in people who face an increased risk of the disorder.
"Diuretics, historically the first choice in treating hypertension and still the most cost-effective, have along with beta-blockers fallen out of favor," said Prakash Deedwania, M.D., professor of medicine at University of California, San Francisco at Fresno. The drugs may increase the risk of diabetes in a couple of different ways: Higher doses of thiazide diuretics (i.e., ≥25 mg/day) have been shown to worsen glycemic control, while even average doses of beta blockers can reduce insulin sensitivity. Evidence suggests, however, that these drugs work synergistically with other types of hypertension drugs including ACE inhibitors and ARBs, he said, which have been shown to reduce the incidence of diabetes.
Meanwhile, weight loss and regular physical activity remain the most effective ways to prevent and improve both hypertension and diabetes. “Physical activity and modest weight loss have been shown to lower type 2 diabetes risk by up to 58% in high-risk populations,” according to a joint position statement issued by the American College of Sports Medicine and the American Diabetes Association.
“Physical activity and structured exercise are both critically important for preventing type 2 diabetes, particularly among people who already have other chronic metabolic conditions like hypertension and insulin resistance,” said Sheri Colberg-Ochs, PhD, lead author of the position statement and professor of exercise science at Old Dominion University in Norfolk. “Being active is one of the best ways to keep insulin working better.”
It is predicted that by 2025, 1.56 billion people worldwide will have hypertension and that by 2030 an estimated 366 million people will have diabetes. Of these, the vast majority will have type 2 insulin-resistant diabetes.