1. ¹Department of Psychology, University of Turku, Turku, Finland
2. ²Department of Physiology (Sleep Research Unit), University of Turku, Turku, Finland
3. ³Department of Physiology, University of Helsinki, Helsinki, Finland
4. ⁴Department of Statistics, University of Turku, Turku, Finland
5. ⁵Department of Neurology, Turku University Central Hospital, Turku, Finland
6. ⁶Department of Obstetrics and Gynecology, Turku University Central Hospital, Turku, Finland

Correspondence: P Alhola, Department of Psychology, University of Turku, FI-20014 Turku, Finland. E-mail: paula.alhola@utu.fi

Received 1 March 2005; Revised 25 January 2006; Accepted 27 January 2006; Published online 15 March 2006.

Abstract

The objective was to evaluate whether hormone therapy (HT) gives any benefit against the possible impairment of cognitive performance when challenged by acute sleep deprivation. Twenty postmenopausal women volunteered (age range 59–72 years, mean=64.4 years, SD=4.4): 10 HT users and 10 nonusers. Eleven young women served as a control group for the cognitive age effect (age range 20–26 years, mean age 23.1 years, SD=1.6). The subjects spent four consecutive nights at the sleep laboratory and were exposed to acute sleep deprivation of 40 h. Measures of attention (reaction speed and vigilance), alertness, and mood were administered every 2 h during the daytime and every hour during the sleep deprivation night. Postmenopausal women performed slower than young controls, whereas young controls made more errors. In HT users, the recovery night did not fully restore the performance in the simple and two-choice reaction time tasks, but in nonusers it did so. Sleep deprivation had a detrimental, yet reversible effect on vigilance in all groups. In all groups, sleepiness started to increase after 15 h of sleep deprivation and remained elevated in the morning after the recovery night. Prolonged wakefulness or HT had no effect on mood. In conclusion, sleep deprivation impaired cognitive performance in postmenopausal as well as young women. Postmenopausal women kept up their performance at the expense of reaction speed and young women at the expense of accuracy. One night was not enough for HT users to recover from sleep deprivation. Thus, HT gave no benefit in maintaining the attention and alertness during sleep deprivation.