Proper Sleep Patterns Can Offset Inherited Or Genetically Linked Risk Of Heart Disease And Stroke
Researchers from Tulane University, New Orleans have for the first time assessed the impact on the risk of heart
or blood vessel problems from the combination of sleep
patterns and genetic susceptibility to cardiovascular disease. The study, which is published in the European Heart Journal
, found that even if people had a high genetic risk
of heart disease
this appeared to be offset to some extent by good sleep patterns.
The medical researchers, led by Professor Dr Lu Qi, Director of Tulane University Obesity Research Center at Tulane University, New Orleans, USA, looked at genetic variations known as SNPs (single nucleotide polymorphisms) that were already known to be genetically
linked to the development of heart disease
They analysed the SNPs from blood samples taken from 385 292 healthy participants in the UK Biobank project and used them to create a genetic risk score to determine whether the participants were at high, intermediate or low risk of cardiovascular problems.
Dr Qi and his colleagues also created a new, "healthy sleep
score" by asking the participants whether they were a "morning" or an "evening" person, how long they slept for, and whether or not they suffered from insomnia, snoring or frequent, excessive daytime sleepiness. The healthy sleep
score ranged from 0 to 5, with 5 being the healthiest sleep
pattern, representing a 'morning" person, who slept between 7-8 hours a night, without insomnia, snoring or daytime sleepiness.
However, it should be noted that excessive sleep
ie more than 8 hours could lead to a higher risk of getting a stroke
as shown by other studies.
The medical researchers followed the participants for an average of 8.5 years, during which time there were 7280 cases of heart disease
Dr Qi told Thailand Medical
News, "We wanted to test whether the relation between sleep scores and cardiovascular outcomes was different according to the genetic risk. This is the first time this has been done. We also wanted to estimate the proportion of cardiovascular problems that would not have occurred if all participants had a healthy sleep
pattern, if we assume there is a causal relationship."
The team found that compared to those with a sleep
score of 0-1 (unhealthy sleep pattern), participants with a score of 5 had a 35% reduced risk of cardiovascular disease, and a 34% reduced risk of both heart disease
Dr Qi said: "If the link between sleep and cardiovascular disease proves to be causal, then more than a tenth of all heart disease and strokes would not have occurred if all the participants had a healthy sleep
score of 5.
Among people with a healthy sleep
score of 5, there were nearly seven fewer cases of cardiovascular disease per 1000 people per year compared to those with a sleep
score of less than 5."
Looking at the combined effect of sleep score and genetic susceptibility on cardiovascular disease, the researchers found that participants with both a high genetic
risk and a poor sleep
pattern had a more than 2.5-fold greater risk of heart disease
and a 1.5-fold greater risk of stroke compared to those with a low genetic risk and a healthy sleep pattern. This meant that there were 11 more cases of heart disease
and five more cases of stroke
per 1000 people a year among poor sleepers with a
risk compared to good sleepers with a low genetic
risk. However, a healthy sleep pattern compensated slightly for a high genetic risk, with just over a two-fold increased risk for these people.
Dr Qi added, "We found that a high genetic risk
could be partly offset by a healthy sleep
pattern. In addition, we found that people with a low genetic risk
could lose this inherent protection if they had a poor sleep
An individual with a high genetic
risk but a healthy sleep
pattern had a 2.1-fold greater risk of heart disease
and a 1.3-fold greater risk of stroke
compared to someone with a low genetic
risk and a good sleep
pattern. While someone with a low genetic
risk, but an unhealthy sleep
pattern had 1.7-fold greater risk of heart disease
and a 1.6-fold greater risk of stroke
The medical researchers cannot exclude the possibility that a poor sleep
pattern might be indicative of some underlying and undetected health problem that might play a role in the increased risk of cardiovascular disease. However, they tried to minimise this risk by excluding all patients with cardiovascular disease at the start of the study and they also took account of factors that could affect the results and were related to a person's health, such as age, sex, ethnicity, deprivation, physical activity, smoking, alcohol consumption, body mass index, other health problems and family history of heart disease
Dr Qi concluded: "As with other findings from observational studies, our results indicate an association not a causal relation. However, these findings may motivate other investigations and, at least, suggest that it is essential to consider overall sleep
behaviours when considering a person's risk of heart disease
Some limitations of the study include: the researchers relied on the participants reporting their sleep patterns, and this occurred only once at the beginning of the study; the healthy sleep score did not include all sleep problems such as restless legs syndrome; and the majority of UK Biobank participants are of European descent, which may affect the generalisation of the results to other populations.
The researchers are not clear what mechanisms may be responsible for the link between sleep and risk of cardiovascular disease. The researchers say disrupted sleep could upset the hormonal or metabolic regulation of the body, increase the body's 'fight or flight' responses, increase inflammation and disrupt the body's natural circadian rhythm.
Reference: "Sleep patterns, genetic susceptibility, and incident cardiovascular disease: a prospective study of 385 292 UK Biobank participants", European Heart Journal (2019). DOI: 10.1093/eurheartj/ehz849