Time to get serious about sleep

<<The length of telomeres (the end bits of chromosomes) shortens with age, and this process can be accelerated by diseases and other external factors.>>

Singaporeans took it in their stride when a study in 2019 found them to be among the world’s worst sleepers. After all, apart from being a bit tired, what could be so bad about losing some shut-eye?

Plenty, according to researchers from SingHealth Duke-NUS Institute of Precision Medicine (PRISM) and the National Heart Centre Singapore (NHCS).

In a joint study, where participants wore Fitbit trackers, a form of wearable technology (see below), it was found that people who habitually get insufficient sleep tend to have shorter telomeres, a marker of premature ageing. Lack of sleep was also associated with an increased risk of cardiovascular disease.

“The general belief is that a lot of restorative processes take place during sleep. Shortening that period means the cells have less time for the process. Over time, this can potentially be detrimental to health,” said one of the study’s authors, Dr Lim Weng Khong, Chief Information Officer, PRISM.

Biological age affected

The researchers found that Singaporeans slept, on average, only 6 hours 28 minutes each night, far less than the recommended seven to nine hours. More importantly, those who slept less than five hours had considerably shorter telomeres.

Telomeres are the end bits of chromosomes. Each time cells divide, their telomeres get shorter.

Using whole genome sequencing, researchers were able to derive the telomere length of each study volunteer.

“Cells divide all the time as we go about our daily lives, so telomere shortening is a normal and continuous process. In general, telomere length is correlated with chronological age, or age as defined by the year of birth,” said Dr Lim, who is also an assistant professor with the Cancer and Stem Cell Biology Programme at Duke-NUS Medical School.

If there is no disease, telomeres generally do not shorten so fast. But they still shorten as we age. So, if you compare the telomere of a 20-year-old person and that of an 80-year-old person, there will be substantial differences. Certain diseases or external factors can speed up the process and shorten telomeres prematurely.

“For instance, dyskeratosis congenita, a rare genetic condition, is associated with short telomeres and bone marrow failure. Other stresses to the body, such as environmental pollution or inadequate sleep, can also accelerate telomere shortening,” he said.

Using Fitbit trackers in the study

In their study, the research team did not use the usual questionnaires to get their information but Fitbit trackers, which are fitness trackers worn on the wrists. More than 480 healthy volunteers wore them for a week, giving researchers an insight into their sleep patterns. Dr Lim said past studies were done using questionnaires, but he believes they are not as reliable as wearable technology.

“Generally, people give imprecise answers on questionnaires. Those who sleep a lot or very little find it easier to estimate their sleep hours. Those who get six to nine hours tend to just report a number that is close to the recommended number — seven hours, for instance. But with wearables, we get more precise answers down to the minute.”

He said that with most people owning some form of fitness tracking device, research using consumer-grade wearables is likely to be the future of biomedical studies.