Fluid Composition Differences in Women and Men with Obstructive Sleep Apnea

David Nicholl, MD

Credit: University of British Columbia

New data indicate that women with obstructive sleep apnea exhibit a tendency towards increased fluid retention when compared with men affected by the condition.¹

Before treatment with continuous positive airway pressure (CPAP) therapy, total body water was found to be similar between sexes. Investigators observed increased extracellular water and decreases in intracellular water and phase angle in women compared with men. However, the findings reported no sex differences in response to CPAP treatment, indicating that CPAP has a similar effect on fluid balance in men and women living with OSA.

Obstructive sleep apnea has been associated with an increased risk of cardiovascular and renal diseases, which are also prone to fluid retention. According to the study, these previous findings suggest that fluid balance may play a role in the pathogenesis of obstructive sleep apnea and these conditions.

Existing evidence has also shown that a nocturnal rostral fluid shift contributes to the pathogenesis of obstructive sleep apnea in men more than women. It is possible that there may be sex differences in body fluid composition that predispose men to more severe obstructive sleep apnea as a consequence of an underlying volume-expanded state, the study stated.

The team of investigators, led by David Nicholl, MD, Division of Nephrology, Department of Medicine, Royal Inland Hospital, University of British Columbia, Kamloops, British Columbia, Canada, evaluated a group of 29 participants (10 women and 19 men) with symptomatic obstructive sleep apnea. Participants were assessed pre- and post-CPAP treatment. Investigators reported that participants were incident, sodium-replete, and otherwise healthy. Bioimpedance analysis was used to measure several body fluid composition parameters, including fat-free mass (FFM, % body mass), total body water (TBW, %FFM), extracellular and intracellular water (ECW and ICW, %TBW), and phase angle (°).

Investigators stated that the results of this study have important implications for the treatment of obstructive sleep apnea in women. CPAP treatment may be equally effective in improving fluid balance in women with the condition as it is in men. These findings could help to improve the diagnosis and treatment of obstructive sleep apnea in women and reduce the risk of cardiovascular and renal diseases associated with the condition.

Overall, the team noted that the evidence exhibited that women with obstructive sleep apnea have baseline body fluid composition parameters favoring volume expansion compared with men. Although CPAP treatment showed comparative effects on fluid balance in men and women with the disorder, further studies are needed to investigate the mechanisms underlying sex differences in body fluid composition in obstructive sleep apnea and the impact these differences have on cardiovascular and renal outcomes.

References:

1. Nicholl, D. D. M., Hanly, P. J., MacRae, J. M., Zalucky, A. A., Handley, G. B., Sola, D. Y., & Ahmed, S. B. (2023). Sex differences in body fluid composition in humans with obstructive sleep apnea before and after CPAP therapy. Physiological Reports, 11, e15677. https://doi.org/10.14814/phy2.15677