Sleeping too little or too much, snoring, daytime sleepiness and insomnia may all increase the risk of glaucoma, a common eye condition that affects millions of people and can lead to blindness, according to a decade-long study.
It is well known that sleeping badly can affect judgment, mood, ability to learn and retain information, and may increase the risk of serious accidents and injury.
Now researchers are focusing on the long-term consequences of poor sleep. They have conducted the world’s first large prospective cohort study to look comprehensively at sleep behaviours and patterns and glaucoma. It involved more than 400,000 people in the UK.
The results, published in the journal BMJ Open, suggest that people who have unhealthy sleep patterns have an increased risk of developing glaucoma. This can lead to loss of vision if not diagnosed and treated early. Glaucoma will likely affect 112 million people worldwide by 2040.
“Snoring, daytime sleepiness, insomnia, and short/long duration, individually or jointly, were all associated with the risk of glaucoma,” concluded the international team of academics, led by researchers from Beijing, China.
“These findings underscore the need for sleep intervention for individuals at high risk of glaucoma as well as potential ophthalmologic screening among individuals with chronic sleep problems for glaucoma prevention.”
The researchers said the study underlined the critical importance of adopting and maintaining healthy sleep patterns and behaviours. The findings also underscore the need for sleep therapy in people at high risk of glaucoma as well as eye checks among those with chronic sleep disorders to check for early signs of the condition, they added.
Characterised by progressive loss of light sensitive cells in the eye and optic nerve damage, the causes of glaucoma are still poorly understood. Left untreated, it can lead to irreversible blindness.
Previously published research had suggested that sleep disorders may be an important risk factor.
To explore these issues further, the researchers set out to examine the risk of glaucoma among people with different sleep behaviours: insomnia; too much or too little sleep; night or morning chronotypes (“owls” and “larks”); daytime sleepiness; and snoring.
The research examined data from 409,053 people who are taking part in the UK Biobank study.
People aged 40 to 69 were recruited to the study between 2006 and 2010 and were followed up until March 2021 to see whether they had been diagnosed with glaucoma. Information about their sleep habits was collected when they joined the study.
Normal sleep duration was defined as between seven and nine hours, with too little or too much defined as outside this range. The person’s chronotype was defined according to whether they described themselves as more of a morning lark or night owl.
During an average follow-up period of almost 11 years, 8,690 cases of glaucoma were identified. With the exception of chronotypes, the other four sleep patterns and behaviours were all associated with varying degrees of heightened glaucoma risk, the BMJ Open said.
The researchers found that compared with people who had a healthy sleep pattern, snoring and daytime sleepiness carried an 11% increased risk of glaucoma. Meanwhile, insomnia and sleeping too much or too little was linked to a 13% increased risk.
The study was observational so a caused cannot be established. It also relied on self reporting rather than objective measurement, the researchers acknowledged. Glaucoma might itself influence sleep patterns, rather than the other way round, they added.
But there are plausible biological explanations for the associations found between sleep disturbance and glaucoma, the researchers said.
The internal pressure of the eye, a key factor in the development of glaucoma, rises when a person is lying down and when sleep hormones are out of kilter, as occurs in insomnia, they explained.
Depression and anxiety, which often go hand in hand with insomnia, may also increase the internal eye pressure. Similarly, episodes of low levels of cellular oxygen, caused by sudden stopping of breathing during sleep, might cause direct damage to the optic nerve, it has also been suggested.