Childhood obesity (search) and asthma (search) may be connected, but it’s not clear which comes first.

Children with an active wheeze had significantly higher BMI (search) and a greater prevalence of obesity, write researchers. Although there is speculation that asthma predisposes to obesity by reducing physical activity, this has not been shown to be the case. However, recent studies show that obesity precedes the development of asthma.

Both conditions are rising among American kids and adults, and asthma is increasing in developing countries worldwide.

There seems to be a relationship between asthma and obesity — and trouble breathing during sleep could be part of the puzzle, a new study shows.

Sleep-disordered breathing (search), characterized by snoring, could be the pathway mediating asthma and obesity.

That’s the latest news in the ongoing debate about asthma and obesity.

New Findings on Obesity and Asthma

Doctors at Cleveland’s Case School of Medicine recently studied 788 kids aged 8-11 years for asthma, wheeze, obesity, and breathing problems during sleep. The researchers made sure enough minority and prematurely born children were included.

The children’s height, weight, and history of wheeze and asthma were noted. The kids took a breathing test and sleep studies were done at home using monitors. Disordered sleep disturbances were defined either by sleep apnea or by snoring habits. In sleep apnea, people regularly stop breathing for 10 seconds or longer during sleep.

The vast majority of the kids (600) had no breathing problems. Kids with wheezing/asthma had the usual risk factors such as being male, black, born prematurely, and had a mother with a history of asthma. Yet kids with wheezing/asthma were also more likely to have a higher BMI.

Obesity was significantly associated with both asthma and wheeze. It nearly doubled the risk of asthma, raising the risk by 1.8 times. Obesity also raised the risk of wheeze 1.6 times.

By comparison, about 14 percent of the kids without wheeze or asthma were classified as obese — identified as being heavier than 95 percent of their peers.

Does Sleep Play a Role?

Problems breathing during sleep also seemed to be important.

About one in three children with asthma or wheezing had sleep-disordered breathing. In contrast, only about one in six kids without wheezing or asthma had sleep-disordered breathing.

“Children with sleep-disordered breathing had nearly twice the odds of wheeze compared with those without,” write Loreto Sulit, MD, and colleagues.

Taking into account sleep-disordered breathing weakened the association between wheezing and obesity, but it did not alter the link between asthma and obesity.

Which Comes First: Asthma or Obesity?

If asthma and obesity are intertwined, it’s still not clear how that works.

Perhaps obesity constricts airways, say the researchers. Or maybe obesity triggers asthma through hormonally driven inflammation, they note. Then again, children with asthma may be less active, driving them towards obesity, say the researchers.

They’re not sure. Their study didn’t have objective measures of the kids’ physical activity, so they can’t say either way.

The study appears in the March 15 issue of the American Journal of Respiratory and Critical Care Medicine.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Sulit, L. American Journal of Respiratory and Critical Care Medicine, March 15, 2005; vol 171: pp 659-664. WebMD Medical News: “The Asthma-Obesity Connection.” WebMD Medical Reference from Healthwise: “Sleep Apnea — Topic Overview.” News release, American Thoracic Society.