The impact of obstructive sleep apnea on diabetes was unknown, until now.
A new study posits that low oxygen levels in the blood (hypoxemia) during sleep are linked with diabetic nephropathy and renal function in patients with type 2 diabetes. The study, which was was published inDiabetes Technology & Therapeutics, examined 800 patients from 12 hospitals.
Patients’ sleep was evaluated through a portable monitor for parameters like the apnea-hypopnea index, which is the number of apnea and hypopnea episodes that occur during sleep divided by the total sleep time. Sleep apnea was defined as an 80% reduction in airflow relative to baseline that lasts at least 10 seconds, and hypopnea was defined as a reduction of at least 30% of the airflow and a 4% or more reduction in oxygen saturation.
The study participants spent 1 night with a nasal cannula attached to a pressure transducer and a pulse oximeter that they wore on their finger.
Other parameters examined included oxygen desaturation index, oxygen saturation, and the amount of time when patients’ oxygen saturation levels were below 90% or 85%. (The researchers noted that in previous small studies, factors like oxygen desaturation index and blood oxygen saturation were associated with diabetes complications.)
In this study, chronic diabetes complications were defined as diabetic retinopathy, diabetic nephropathy, and diabetic peripheral neuropathy.
In the cohort, around 30% had diabetic retinopathy, and 4% had proliferative diabetic retinopathy. Around 40% had diabetic nephropathy, and 57.8% had diabetic peripheral neuropathy. Prevalence of microalbuminuria, macroalbuminuria, and renal insufficiency among the patients with diabetic nephropathy were about 24%, 11%, and 4%, respectively.
The researchers discovered that the cumulative time when patients’ oxygen saturation levels were below 90% was associated with diabetic nephropathy, after adjusting for factors like age, sex, body mass index, and use of angiotensin-converting enzyme inhibitor or angiotensin receptor blocker drugs within 1 week.
The average oxygen saturation and oxygen saturation levels below 90% were associated with microalbuminuria, while oxygen saturation levels below 90% and 85% were linked with macroalbuminuria.
“Among all indicators, CT90% [cumulative time of oxygen saturation below 90%] was the only parameter that was simultaneously associated with DN [diabetic nephropathy], microalbuminuria, and macroalbuminuria and may be the most promising parameter to study in the future,” the researchers stated.
They noted that microalbuminuria, an early stage of diabetic nephropathy, can be reversed if treated properly. Their findings also suggested that the total time of hypoxemia, rather than the frequency of desaturation, could be more important to diabetic nephropathy.
Oxygen desaturation index, low oxygen saturation, and oxygen saturation levels below 85% were associated were independent-associated factors for renal insufficiency, as well.
The study authors posited that hypoxemia seemed to “more sensitively reflect” the link between obstructive sleep apnea and diabetic microvascular complications than the apnea-hypopnea index.
Obstructive sleep apnea is common among patients with type 2 diabetes; estimates range from around 53% to 86%, which is higher than the general public’s prevalence of obstructive sleep apnea.