Too short, long sleep linked to incurable lung disease

People who regularly sleep for more than 11 hours or less than four hours are 2-3 times more likely to have the incurable lung disease, pulmonary fibrosis, compared to those that sleep for seven hours in a day, researchers have found.

They attribute this association to the body clock.

The study, published in the journal Proceedings of the National Academy of Sciences, also reveals that targeting the body clock reduces fibrosis in vitro, revealing a potential target for this incurable disease that kills about 5,000 people, a year in the UK,the same number as leukaemia.

"Pulmonary fibrosis is a devastating condition which is incurable at present. Therefore, the discovery that the body clock is potentially a key player potentially opens new ways to treat or prevent the condition," said study lead author John Blaikley from The University of Manchester in UK.

"More work need to be done around studying the association between pulmonary fibrosis and sleep duration to establish both causation and reproducibility," Blaikley said.

"If these results are confirmed, then sleeping for the optimal time may reduce the impact of this devastating disease," he added.

Our internal body clocks regulate nearly every cell in the human body, driving 24-hour cycles in many processes such as sleeping, hormone secretion and metabolism.

In the lungs, the clock is mainly located in the main air carrying passages - the airways.

However, the team discovered that in people with lung fibrosis, these clock oscillations extend out to the small air spaces, called alveoli.

Studies in mice revealed that by altering the clock mechanism it was possible to disrupt the fibrotic process making the animals more likely to develop pulmonary fibrosis.

The researchers then showed, that pulmonary fibrosis is associated with short and long sleep duration using human data from the UK Biobank.

The link between sleep duration and lung fibrosis is similar in strength to other known risk factors for this disease.

People who report they regularly sleep four hours or less in a day doubled their chance of having pulmonary fibrosis while those sleeping 11 hours or longer in a day tripled their chance of having the disease, compared to those sleeping seven hours per day.

Smaller, but still elevated, risks were also seen in people who like to stay up late at night or those who do shift work.

The researchers explain their findings by the discovery that a core clock protein (REVERBa) which alters the production of a key protein in lung fibrosis (collagen).

This is an exciting finding, because chemical compounds can alter the function of REVERBa, said the researchers.

The researchers were able to show that one of these REVERBa compounds can reduce collagen in lung slices from people with this disease.

The discovery that the clock plays a role in fibrosis suggests that altering these oscillations could become an important therapeutic approach, the research said.