Nocturnal transcutaneous carbon dioxide tension in postmenopausal estrogen users and non-users

The effect of menopause on breathing is not fully understood. We have previously shown that postmenopausal women have a higher sleep-induced increase in transcutaneously measured carbon dioxide tension (TcCO(2)) than premenopausal women. Therefore, we hypothesized that estrogen therapy (ET) would normalize this sleep-induced TcCO(2) increase.

Nine postmenopausal ET users and nine non-users went through an overnight polygraphic sleep study including continuous monitoring of TcCO(2).

TcCO(2) levels were higher during sleep than evening wakefulness (awake median 6.55 kPa versus sleep median 6.90 kPa, P = 0.001). ET users had a greater sleep-induced increase in TcCO(2) than non-users when comparing the difference between wakefulness and slow-wave sleep (0.85 kPa versus 0.28 kPa, P = 0.004). Lower sleep efficiency was associated with higher sleep-induced increase in TcCO(2).

In contrast to our initial hypothesis, postmenopausal ET users have a higher sleep-induced increase in TcCO(2) than women without ET. Thus, TcCO(2) may be sensitive in measuring the peripheral estrogen effect. These findings warrant placebo-controlled intervention studies to confirm the effects of ET on TcCO(2) measurements.