Circadian rhythms are the internal ‘clocks’ that nearly every tissue and cell runs in the background, collectively tuned to the 24-hour day-night cycle. Aside from being the bane of shift workers, disruption of the body’s circadian rhythm has been linked to medical conditions as varied as heart attacks, Alzheimer’s disease and cancer. It’s also known to regulate blood pressure (BP), which directly impacts heart health.
These rhythms differ widely between individuals. You probably know a ‘morning person,’ an early riser who displays peak alertness first thing, and a ‘night owl,’ someone who prefers sleeping in and exhibits peak alertness later in the day, sometimes into the evening. A new study by researchers from the University of Dundee, Scotland, and Helmholtz Munich, a German research center, found that these body clock behaviors, called ‘chronotypes,’ influence the effectiveness of BP medications, or antihypertensives.
“We all have an internal biological clock which determines our chronotype – whether we are more of a ‘morning’ or ‘evening’ person,” said Kenneth Dyar, a circadian biologist from Helmholtz Munich and the study’s co-lead and co-corresponding author. “This internal time is genetically determined and affects biological functions over 24 hours, including gene expression, blood pressure rhythms, and how we respond to medications.”
The researchers recruited 5,358 participants with high BP and randomized them to receive either morning or evening doses of their antihypertensive medication. Each participant’s chronotype was determined through a questionnaire and a self-reported preference for mornings or evenings. The researchers analyzed associations between medication dosing time and chronotype and explored their combined effect on hospitalization for non-fatal heart attack or non-fatal stroke.
They observed a lower rate of non-fatal heart attacks when dosing time was synced with chronotype. That is, morning people who took their meds in the morning and night owls who took their meds in the evening were less likely to be hospitalized for a non-fatal heart attack. There was no observable association between dose time and chronotype for stroke events.
Participants with an evening chronotype were associated with an increased risk of hospitalization for non-fatal heart attack if they took their antihypertensive in the morning and a reduced risk if they took it in the evening.
“Our research has shown for the first time considering chronotype when deciding dosing time of antihypertensives – personalized chronotherapy – could reduce the risk of heart attack,” said Filippo Pigazzani, honorary consultant cardiologist at the University of Dundee’s School of Medicine and the study’s other lead and corresponding author.
‘Personalized chronotherapy’ is as it sounds: treating a person according to their circadian rhythm to make the treatment more effective. The researchers say their findings suggest that doctors should consider individual chronotypes when prescribing antihypertensive medication – it’s an easy-to-assess way of potentially improving outcomes using existing therapies.
“It’s important for physicians to remember that not all patients are the same,” Dyar said. “Humans show wide inter-individual differences in their chronotype, and these personal differences are known to affect disease risk.”
The study was published in the journal eClinical Medicine.
Source: University of Dundee
