Effects of hormone replacement therapy on olfactory sensitivity: cross-sectional and longitudinal studies

To determine whether hormone replacement therapy (HRT) preserved or improved olfactory sensitivity in healthy postmenopausal women.

Sixty-two postmenopausal women participated in a cross-sectional study of olfactory sensitivity involving detection, intensity discrimination, quality discrimination and two measures of quality recognition. In addition, 24 postmenopausal women participated in a longitudinal study of olfactory sensitivity. This study allowed for the measurement of estrogen effects (while holding practice effects constant) and the measurement of practice effects (while holding HRT conditions constant).

In the cross-sectional study, we were unable to detect any differences between those receiving HRT and those not receiving HRT. Duration of exposure to HRT was examined by selecting women who had 5 or more years of exposure to their HRT regimen. Even after the data were reorganized into those for opposed- and unopposed-estrogen use, we were unable to detect any differences. However, olfactory threshold increased as a function of increasing age, regardless of HRT status. A gradual decrease in ability to detect odors was observed from the 4th to the 6th decade, with a greater decrease between the 6th and 7th decades. In the longitudinal study, no effects of HRT were detected even when practice effects were uncontrolled. Practice effects were assessed both between and within subjects. No effects of practice were detected when initial baseline performance was used as a covariate.

Although prophylactic HRT has been suggested to be associated with improved olfactory function, we find that its use in healthy postmenopausal women does not enhance performance in a wide range of olfactory tasks.