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Sleep apnea linked to Alzheimer's disease: Which comes first?

Kathleen Blanchard's picture
Sleep disordered breathing linked to Alzheimer's. Which comes first?

Estimates suggest more than 1 in 15 people suffer from sleep apnea. A new study shows the sleep disorder is also linked to Alzheimer’s disease.

A study presented at the ATS 2013 International Conference found markers in spinal fluid of people with sleep apnea that are also found with Alzheimer’s disease (AD).

Researchers say the finding poses the question about whether early stages of Alzheimer’s disease – before symptoms appear - make people more prone to sleep disordered breathing (SDB) that is so prevalent among the elderly.

Ricardo S. Osorio, MD, a research assistant professor at NYU School of Medicine who led the investigation said in a press release, "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."

Osorio explains SDB becomes more prevalent with aging and affects somewhere between 30 and 60 percent of people over age 65.

Rates of sleep apnea jump dramatically the 10 to 20 percent seen in middle age.

Biochemical markers of Alzheimer’s disease are also present 10 to 20 years before the disease shows any symptoms.

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Researchers tested 68 cognitively intact seniors at home for SDB and at least one sign of Alzheimer’s disease for the study.

Biomarkers for Alzheimer’s disease were only found among lean study participants who had sleep apnea.

The researchers tested the cerebrospinal fluids for P-Tau, T-Tau and Aβ42. They also used FDG-PET scans that image glucose metabolism in the brain and another specialized PET scan imaging of the brain.

Cerebrospinal fluid markers strongly correlated with the severity sleep disordered breathing.

The correlation was so strong, the research team is planning studies to treat 200 patients with SBD and no clinical symptoms of Alzheimer’s disease to find out which comes first? Does sleep apnea worsen with Alzheimer’s disease or does SBD develop with aging because Alzheimer’s disease is already ‘brewing’?

Sleep apnea has been linked to a variety of health problems, including difficulty thinking, diabetes, higher risk of cancer and low energy.

"If the biomarkers change, it may indicate that SDB is causing AD," explained Dr. Osorio. The plan is to re-evaluate the study group after 6-months of CPAP. Osorio said if there is no change, it probably means Alzheimer’s disease was going to develop with or without treatment and that Alzheimer’s disease may be causing sleep apnea. It might also be that sleep disordered breathing and Alzheimer’s co-exist as we become older.

May 19, 2013

Image credit: Pixabay