ASN's Mission

ASN leads the fight to prevent, treat, and cure kidney diseases throughout the world by educating health professionals and scientists, advancing research and innovation, communicating new knowledge, and advocating for the highest quality care for patients.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005


The Latest on Twitter

Kidney Week

Abstract: TH-PO749

Sex Differences in Bioimpedance in Humans with Obstructive Sleep Apnea with Normal Kidney Function Before and After Continuous Positive Airway Pressure Therapy

Session Information

Category: Women’s Health and Kidney Diseases

  • 2000 Women’s Health and Kidney Diseases


  • Nicholl, David Donald McTavish, Western University, London, Ontario, Canada
  • Hanly, Patrick, University of Calgary, Calgary, Alberta, Canada
  • Zalucky, Ann A., University of Toronto, Toronto, Ontario, Canada
  • MacRae, Jennifer M., University of Calgary, Calgary, Alberta, Canada
  • Handley, George, Healthy Heart Sleep Company, Calgary, Alberta, Canada
  • Sola, Darlene Y., University of Calgary, Calgary, Alberta, Canada
  • Ahmed, Sofia B., University of Calgary, Calgary, Alberta, Canada

Sex differences exist in obstructive sleep apnea (OSA) and chronic kidney disease (CKD), both of which are strongly associated and predispose patients to expanded total body water (TBW) and aberrant volume redistribution, resulting in significant morbidity. Continuous positive airway pressure (CPAP) therapy is an effective treatment for OSA which may alleviate this predisposition. While there are established sex differences in the pathophysiology of OSA and CKD, whether sex differences exist in TBW and other bioimpedance parameters in OSA subjects with normal kidney function and the impact of CPAP therapy remains unknown.


Twenty-nine (10 women, 19 men; age 49±2y) incident, otherwise healthy, and sodium replete OSA subjects (oxygen desaturation index [ODI] >15h-1) with and nocturnal hypoxemia (SaO2<90% for >12%/night) were studied pre- and post-CPAP therapy (>4h/night x 4 weeks) using bioimpedance technology. Total body water (TBW), extracellular and intracellular fluid volumes (ECF and ICF), ECF:TBW, ECF:ICF, fat free mass (FFM), body mass index (BMI) and other bioimpedance and anthropometric parameters were measured and evaluated for sex differences before and after CPAP therapy.


Pre-CPAP, TBW (74.6±0.4 vs 74.3±0.2% of FFM, p=0.14; all values women vs men) and BMI (36±3 vs 35±1 kg/m2, p=0.9) were similar between sexes, though FFM (56.3±1.7 vs 71.7±1.5% of weight, p<0.001) and absolute TBW (42.4±3.0 vs 57.1±1.6L, p<0.001) were lower in women. The proportion of ECF:TBW (0.50±0.006 vs 0.44±0.009, p<0.001) and ECF:ICF (1.00±0.002 vs 0.80±0.004, p<0.001) was increased in women despite overall reduced absolute ECF (21.3±1.7 vs 25.2±0.8L, p=0.006) and ICF (21.1±1.2 vs 31.9±1.0L, p<0.001) compared to men. Though CPAP corrected both OSA (ODI: 47.4±4.4 vs 3.3±0.4h-1, p<0.001) and nocturnal hypoxemia (46.2±5.7 vs 8.3±2.7%, p<0.001), there were no within sex differences in bioimpedance or arthropometric parameters in response to CPAP therapy.


Women with OSA had expanded ECF compared to men. Differences in TBW distribution may contribute to sex differences in the pathophysiology of OSA in humans with normal kidney function. CPAP therapy for 1 month did not mitigate these differences.