Sleep apnea may be bad for kidneys

Having sleep apnea may increase the risk of chronic kidney disease, according to a report from Taiwan.

Researchers analyzed data from 2000 through 2010 on 8,600 adults diagnosed with sleep apnea and four times as many adults of similar age, sex and monthly income without sleep apnea, using Taiwan’s National Health Insurance Research Database.

They found 157 new cases of chronic kidney disease among people with sleep apnea and 298 cases in the comparison group, according to Yung-Tai Chen of Taipei City Hospital Heping Fuyou Branch in Taiwan and coauthors.

After taking other health factors into account, sleep apnea increased the risk of kidney disease by 58%. By comparison, hypertension (a known risk factor for kidney disease) increased the risk by 17%. Diabetes was a stronger predictor than both other factors, more than doubling the risk of kidney disease, the research team reported online February 1 in Respirology.

Intermittent low oxygen levels during the night and fragmented sleep patterns may activate higher blood pressure, which would damage the kidneys and could make individuals more susceptible to chronic kidney disease, said Tetyana Kendzerska of the University of Toronto Institute for Clinical Evaluative Sciences, who was not part of the study in Taiwan.

But, “the findings from this study are limited by lack of information on sleep apnea and chronic kidney disease severity given that these conditions were defined through the health administrative data,” Kendzerska said.

Factors like obesity and smoking status are also important for kidney risk but were not included in the assessment, she told Reuters Health by email.

“So, instead of concluding that sleep apnea has the same impact as high blood pressure on the kidney, I would rather conclude that this study suggests that the association between sleep apnea and chronic kidney disease may exist,” and should be validated with more powerful studies, she said.

Moderate to severe obstructive sleep apnea can be treated with continuous positive airway pressure (CPAP) at night which may decrease high blood pressure and mitigate kidney risk, Kendzerska said.

“These findings raise the issue of whether the relationship between sleep apnea and chronic kidney disease is unidirectional or bidirectional,” she said. “If the importance of sleep apnea and preventive effect of treatment will be confirmed in further studies, sleep apnea should be added to the list of modifiable risk factors considered in (chronic kidney disease) risk assessment.”