title: Menopausal estrogen therapy predicts better nocturnal oxyhemoglobin saturation.
abstract: OBJECTIVE
  The respiratory responses in the few previous studies evaluating the effects of short-term unopposed estrogen therapy on breathing in postmenopausal women have been inconsistent. We performed a study to investigate whether long-term estrogen therapy would prevent age-related decline in nocturnal arterial oxyhemoglobin saturation and whether higher serum estradiol concentration is associated with better arterial oxyhemoglobin saturation.
  
  
  METHODS
  Sixty-four healthy postmenopausal women were followed-up for 5 years in a 5-year prospective open follow-up study. The women were users or non-users of estrogen therapy according to their personal preference.
  
  
  RESULTS
  Mean overnight arterial oxyhemoglobin saturation was similar at baseline (94.3 +/- 1.1%) and after follow-up (94.5 +/- 1.6%). Present estrogen users had higher mean arterial oxyhemoglobin saturation (95.2 +/- 1.4%) than present non-users (94.0 +/- 1.5%), when adjusted for age and body mass index (p = 0.042). The change in mean arterial oxyhemoglobin saturation during follow-up was not associated with serum estradiol concentration at baseline but associated with estradiol at follow-up (p = 0.042), when adjusted for age and body mass index. At follow-up, women with higher serum estradiol concentration had also higher mean nocturnal arterial oxyhemoglobin saturation (Pearson r = 0.29, p = 0.019) and lower apnea-hypopnea index (Spearman r = -0.28, p = 0.031). The pooled current estrogen users spent proportionally less time with SaO(2) below 90% than non-users (ANCOVA adjusted for age and BMI, p = 0.017).
  
  
  CONCLUSIONS
  Estrogen use and especially high serum estradiol concentration predict higher mean overnight arterial oxyhemoglobin saturation. The present data suggest that estrogen therapy has favorable respiratory effects.
authors: Sleep Research Unit, Department of Physiology, University of Turku, Turku, Finland. tarja.saaresranta@tyks.fi
authors: Tarja
authors: T
authors: Saaresranta
authors: Päivi
authors: P
authors: Polo-Kantola
authors: Irina
authors: I
authors: Virtanen
authors: Tero
authors: T
authors: Vahlberg
authors: Kerttu
authors: K
authors: Irjala
authors: Olli
authors: O
authors: Polo