Chronotherapy in Hypertension - a Study of Blood Pressure Levels Following Intake of Antihypertensive Medication in the Morning or at Bedtime

High blood pressure (hypertension, HT) is very common and can lead to serious cardiovascular complications and premature death. Despite effective drug treatment many patients do not reach the blood pressure goal. No new antihypertensive drugs have been developed lately, so there is a need for other strategies to increase attainment of goals and diminish the rate of complications. The circadian rhythm can affect sleep, body temperature, hormone levels, metabolism and the effect of drugs. The impact of antihypertensive treatment in the short and long run was described in a large randomized study in primary health care where individuals with hypertension were randomly assigned to take the drugs in the morning or at bedtime. Intake at bedtime resulted in lower blood pressure, better kidney function and lower LDL-cholesterol. Further, after a mean time follow-up of 6 years a 50% reduction of cardiovascular death was seen. There was by time running a difference in antihypertensive drugs and also co-morbidity between the groups. Despite this, there is a need to investigate if chronotherapy might play a role in antihypertensive care.

The aim of the study is to investigate the effect of intake of drugs in the morning compared to at bed-time.

Methods: Patients 40-75 years, will be recruited from two primary health care centers and one clinic of internal medicine. Medical history, current medication will be recorded. Office blood pressure, body height and weight, ECG and ambulatory blood pressure measurement (ABPM) will be performed. Blood will be analyzed for fasting blood glucose, LDL and HDL-cholesterol and creatinine.

After inclusion in the study the patients are randomly, by clinic, allocated to take their antihypertensive drugs in the morning or at bed-time during 8 week. The ordinary medication is used during the study period. The patients are instructed to keep a diary on wake-up and bed-times, side effects, sleep quality and other experiences during therapy. After 8 weeks the investigations at base-line are repeated and a visual analogue scale on sleep, daytime tiredness and urine voiding is recorded. The patients shift to intake of medication on the opposite time of day for 8 weeks. The study is completed with a repeated investigation as above. The analyses of data is performed by researchers of the team that are not aware of the patients' allocation. The diaries will be a base for later in-depth-interviews with a part of the patients. The analyses will be intention-to-treat using appropriate methods for the data. Office blood pressure, blood lipids and kidney function at baseline, 8 and 16 weeks, as well as sleep duration, urine voiding at night will be analyzed. ABPM will be analyzed using mean blood pressure around-the-clock, daytime and nighttime blood pressure, dipping and morning surge.