Teens who stay up late more likely to have allergies and asthma, study says

Humans are naturally programmed to abide by the laws of nature when it comes following the sun's patterns for waking and sleeping. Teenagers, of course, often follow their own laws for hitting the sack.

But staying up late doesn't just lead to grumpy youngsters at breakfast. A new study shows that teen night owls are significantly more likely to suffer respiratory problems.

"We found that the risk of having asthma is approximately three times higher among the night teens compared to the morning teens," said Subhabrata Moitra, a post-doctoral fellow in pulmonary medicine at the University of Alberta.

"The risk of having any allergy was also approximately three times higher in the night teens," Moitra, the study's principal researcher, told CBC Radio's Edmonton AM on Wednesday.

The study talked to 1,684 adolescents, aged 13 and 14, in the Indian state of West Bengal about their sleep preferences and respiratory health. It also took into account other known contributing factors to asthma and allergies, such as pets, family history, exposure to second-hand smoke and whether they lived in an urban or rural area.

Moitra said the cross-sectional, observational study isn't able to pinpoint a reason for the link but he believes it has to do with a teen's production of melatonin, a hormone that helps the body know when it's time to sleep and wake up.

Melatonin can also affect the immune system, he said, adding that the development of asthma and allergies is known to be the result of immune system alterations.

"Allergies and asthma are inflammatory diseases, having tremendous components of inflammatory modulators," he said. "So we can assume that late-night activity could actually hamper the melatonin cycle, which could lead to the altered immune action."

Asthma is the world's most common chronic disease among children. More than 339 million people, including about 3.5 million Canadians, are living with it, according to the World Health Organization.

A teenager's natural sleeping habits should fall under what Moitra called a healthier "lark" behaviour — early to bed, early to rise — but their actions are influenced by other factors, ranging from studies to screens.

Those are habits that need to be broken, Moitra said.

"If they are getting transformed into nighttime people then it is particularly because of some sort of influence like study or late-night activity. But they are basically larks. They are not supposed to be night owls," he said.

"It is very important that there should some parental control in regulation of their nighttime activities."

Researchers plan to follow up with phase two of the study in about 10 years, getting more objective data on participants' lung functions, allergy profiles and sleep patterns. 

In the meantime, Moitra is urging doctors to ask more questions about behaviour when diagnosing allergies and asthma.

"We need to be more vigilant to ask about eating habits, sleeping habits, whether they play outside, because these behaviours can be modified to help get rid of symptoms."