According to the study, these new findings could alter the the treatment of hypertension for millions of people worldwide.
The study was carried out over five years and Professor Ramón C. Hermida, PhD was the lead investigator
. The results have been published in Chronobiology International
. The study found that taking the medication at night time helped keep blood pressure within a normal range and was better at preventing people from developing cardiovascular problems.
The study also showed that taking at least one blood pressure medication at night was the most effective at keeping blood pressure normal during sleep. Taking the medication in the evening was also the best way to control blood pressure during the day.
Dr Michael Smolensky is editor of Chronobiology International. I asked him if he could explain more about the study?
"The MAPEC study used comprehensive 48-hour ambulatory blood pressure monitoring done at least at yearly intervals during the 5.6 yr median duration of treatment per patient to gage the effect of conventional morning timings of BP medications versus the bedtime chronotherapy of BP medications in which one of more of a patient’s several BP medications was ingested at bedtime at the advice of a doctor."
How much more effective was blood pressure medication when taken in the evening instead of the morning?
"The better effect on the sleep-time BP levels resulted in a better normalization of the 24-hour BP pattern – a pattern seen in persons without high BP in which the sleep-time BP declines by 10-20% from the daytime levels. Previous large population-based, long-term outcome studies have found that the sleep-time BP level is a much more sensitive predicator of one risk of dying of cardiovascular disease than the BP level measured during the daytime in the doctor’s office. This suggests the normalization of the sleep-time BP could be a new and important target of BP medications and treatment. Thus, the results of the MAPEC study, showing that the bedtime chronotherapy of at least 1 of several BP medications induces greater reduction of the sleep-time, fits well with the other key findings of the MAPEC study, i.e, that cardiovascular events – heart attacks and strokes -- are reduced to a much greater extent, by one-third, with the bedtime chronotherapy compared to conventional morning-time treatment strategy."
What was the age group of people involved in the study and how many people took part?
"A total of 2156 patients (1044 men/1112 women), mean age 55.6 yrs participated. There were studied for a median duration of 5.6 yrs. This was not a study of the advantage of any particular type of blood pressure medication but rather the concept of whether the timing of BP medication in relation to 24-hour pattern of BP and circadian rhythms of the BP control mechanisms, i.e., morning treatment with all medications versus bedtime chronotherapy with one or more medications, regardless of class of medications."
How can harnessing the power of the body clock make blood pressure medication more effective?
"Systolic and diastolic BP is not constant during the 24 hours but exhibits various types of 24-hour patterns.
The normal 24-hour of BP is characterized by an immediate and substantial rise in BP in the upon arising from bedtime after night-time sleep, elevated BP levels during daytime activity, declining BP levels in the evening, and decreased, by 10-20% BP levels during night-time sleep (relative to daytime activity levels). This type of 24-hour BP pattern is called a ‘dipping pattern’. The normal 24-hour dipping BP pattern is the consequence of day-night differences in posture, activity, stress/emotion and ambient temperature, among other external determinants. However, this 24-hour BP pattern is also the consequence of endogenous (inherited) circadian rhythms in circulating vasoactive chemical agents, such as renin, angiotensin, aldosterone and adrenalin, which directly affect blood volume and blood vessel diameter and as a result systolic and diastolic BP. Most of these chemical agents are synthesized and released during the night-time sleep span."
"While most normotensive and many hypertension patients have dipper BP patterns, a large and increasing proportion of the population have non-dipping 24-hour BP patterns, in which BP levels fail to decline by 10-20% during night-time sleep relative to daytime levels. These patients generally include those whose hypertension occurs secondary due to one more existing medical ailments, such as metabolic syndrome, type II diabetes, kidney disease, certain endocrine (hormone) disorders, sleep apnoea and other sleep disorders, and those 65 yrs and older, for example."
"Timing BP medications, which are intended to block the synthesis and effects of the aforementioned high blood pressure producing chemicals (e.g., renin, angiotensin, aldosterone, adrenalin), at bedtime results in an optimization of their actions, because the medications are delivered at the right biological time to best inhibit the production and actions of these chemical agents that elevate BP. As a result, night-time BP levels are most efficiently reduced and the daytime levels moderated. "
"The bedtime chronotherapy, as compared to conventional morning-time treatment, of BP mediations makes use of the body’s rhythms to optimize their BP-lowering effects, and the bedtime chronotherapy strategy represent s new and cost-effective means of improving BP control, especially sleep-time BP, to better reduce the risk of hypertension patients to heart attack and stroke than conventional morning-time therapy, without the need to increase the number or dose of prescribed medications. In many patients, all this is need is a change in the timing of medications to exert better control and regulation of BP in hypertension."
"Ideally, 24-hour ambulatory BP (AMBP) monitoring is advised to assess BP during the day when awake and during the night while asleep. 24-hour ABPM is also advised to assess that sleep-time and awake-time BP is properly controlled and to be sure sleep-time BP is not lowered too greatly by the bedtime chronotherapy strategy. Unfortunately, in the USA, most healthcare organizations regard 24-hour ABPM as a research tool rather than key clinical tool to properly differentiate normotension versus hypertension as a diagnosis and to assess the achievement of treatment goals, that is the control of both sleep-time and daytime BP levels and the reduction of cardiovascular risk."
According to the American Heart Organisation
, 74.5m people in the United States have hypertension.