Two Studies Find Link Between Sleep Apnea And Asthma, Alzheimer's
May 20, 2013

Two Studies Find Link Between Sleep Apnea And Asthma, Alzheimer’s

Brett Smith for - Your Universe Online

Two new studies to be presented at the American Thoracic Society 2013 International Conference in Philadelphia this week found strong associations between sleep apnea and other disorders.

In one study, published in the American Journal of Respiratory and Critical Care Medicine (AJRCCM), scientists from the University of Wisconsin found a strong connection between sleep apnea and asthma, particularly for those participants who experienced the onset of asthma in their childhood.

"This is the first longitudinal study to suggest a causal relationship between asthma and sleep apnea diagnosed in laboratory-based sleep studies," said Dr. Mihaela Teodorescu, an assistant professor of medicine at Wisconsin.

The researchers used data from a National Institutes of Health (NIH) study that followed approximately 1,500 people since 1988. The team found that people who had asthma were 1.7 times more likely to contract obstructive sleep apnea (OSA) after eight years. For those with a childhood-onset of asthma, researchers found a 2.3-times greater chance of developing sleep apnea.

"Cross-sectional studies have shown that OSA is more common among those with asthma, but those studies weren't designed to address the direction of the relationship,” Teodorescu said.

The Wisconsin team also discovered that the duration of asthma played a role in the chances of developing sleep apnea. For every five years of asthma, the odds of developing OSA after eight years increased by 10 percent.

A second apnea-related study, also appearing in the AJRCCM, and to be presented this week in Philadelphia makes a strong connection between the sleep disorder and developing Alzheimer´s disease in the lean individuals, defined as having a BMI of less than 25.

"It's really a chicken and egg story," said lead researcher Dr. Ricardo S. Osorio, a research assistant professor at New York University´s (NYU) School of Medicine. "Our study did not determine the direction of the causality, and, in fact, didn't uncover a significant association between the two, until we broke out the data on lean and obese patients."

In the study, Osorio and several colleagues from NYU enrolled 68 mentally-normal patients between the ages of 64 and 87. The participants spent two nights being monitored for a form of sleep apnea called sleep-disordered breathing, or SDB. They were also tested for at least one biomarker for Alzheimer´s disease.

The researchers found a direct relationship between the severity of SDB and two different biomarkers for Alzheimer´s.

The team said that these were only preliminary results and they are planning to test the theory that very early stage Alzheimer´s associated with specific biomarkers can lead to SDB. To determine the nature of the association, the NYU team plans to treat study participants with the biomarkers for Alzheimer´s and moderate to severe SDB with continuous positive airway pressure, or CPAP. After a six-month CPAP regimen, they plan to check again for evidence of Alzheimer´s.

"If the biomarkers change, it may indicate that SDB is causing AD," explained Osorio. "If they don't change, the probable conclusion is that these patients are going to develop AD with or without CPAP, and that AD may either be causing the apneas or may simply coexist with SDB as part of aging."

"Sleep apnea skyrockets in the elderly, and this fact hasn't been given the attention it deserves by the sleep world or the Alzheimer's world," he added. "Sleep particularly suffers from an outmoded perception that it is an inactive physiological process, when, in reality, it is a very active part of the day for the brain."