Stress, it's in our blood: Your body clock may determine cardiovascular risks

Monash research has identified that your body clock could influence the time of day and likelihood of experiencing a cardiovascular event, such as a stroke or heart attack.

  • Early risers may have an increased risk of experiencing cardiovascular events earlier in the day; ‘night owls’ may be more at risk in the evening.
  • This is determined by your body clock type and how it responds to stress.
  • Researchers hope these findings and future research will provide clinicians with additional information to improve the treatment of their patients.

Your body clock could influence the time of day and likelihood of cardiovascular events, such as stroke or heart attack, according to new research by Monash University and the University of Birmingham.

A study, published in Frontiers in Physiology, found the way in which blood vessels responded to stress was influenced by whether you were an early riser (‘morning lark’) or liked to stay up late (‘night owl’).

The research showed ‘morning larks’ could have an increased risk of cardiovascular events early in the day, while ‘night owls’ are more at risk later in the evening.

In the study, 312 volunteers completed a questionnaire to assess their body clock type (chronotype) based on their sleeping and waking behaviour. From this group, 20 healthy young individuals with no pre-existing medical conditions were randomly selected to take part in a series of tests in the morning between 8am and 10am, and again in the evening between 6pm and 8pm.

The tests measured participants’ heart rate, arterial pressure and vascular endothelial response – some of the mechanisms that control blood flow through arteries.

Results showed that chronotype has an effect on the ability of blood vessels to respond to stress, with individuals shifted towards the ‘morning lark’ group having reduced response in the morning, and the later ‘night owls’ having a reduced response in the evening.

Lead author, Dr Elise Facer-Childs, fellow in chronobiology at Monash University and research associate at the University of Birmingham in the UK, explains: “Our initial research shows that if early risers were to experience cardiovascular stress in the morning, they may be more likely to experience heart attack or stroke. On the other hand, late risers may be more at risk if exposed to cardiovascular stress in the evening.”

“Although the reasons for this are not yet clear, and our data is in a healthy population, our study shows that an individual’s chronotype could be another factor that should be taken into account when managing patients with pre-existing cardiovascular issues.”

Study senior author, Dr George Balanos, in the School of Sport Exercise and Rehabilitation Sciences at the University of Birmingham, says: “Our data provide an indication that regulation of the cardiovascular system is better at certain times of the day for people with different chronotypes.

“More patient-specific data is needed to support these findings, but ultimately we hope it will provide clinicians with additional information which they can use to improve the treatment of their patients and provide a more individually tailored plan for them."