Effects of manipulating body temperature on sleep in postmenopausal women.

Abstract Study Objectives A decline in sleep quality, slow wave sleep (SWS) and slow wave activity (SWA) are common in older adults. Prior studies have shown that manipulating body temperature during sleep can increase SWS/SWA. The aim of this study was to determine the effects of manipulation of body temperatures during sleep, using a high heat capacity mattress, on SWS/SWA and heart rate in post-menopausal women. Methods Twenty-four healthy postmenopausal women between 40-75 years of age (mean age 62.4 ± 8.2 years, mean BMI 25.4 ± 3.5 kg/m2) were randomized in a single-blind, counterbalanced, cross-over manner to sleep on either a high heat capacity mattress (HHCM) or a low heat capacity mattress (LHCM) a week apart. Sleep was recorded using polysomnography during an 8-hour sleep opportunity. Core and peripheral temperature were recorded using an ingestible capsule and thermochron respectively. Results In comparison to the LHCM, sleep on HHCM exhibited a selective increase in SWS (average increase in Stage N3 of 9.6 minutes (2.1%), p = 0.04) and in slow oscillatory (SO) activity (0.5-1Hz) in the first NREM/REM cycle (p=0.04). In addition, the HHCM induced a greater reduction in core body temperature (p=0.002). The reduction in core body temperature (first 180 minutes after lights out) from LHCM to HHCM was associated (r=0.5, p=0.012) with the increase in SO activity (SO cycle 1 and 2/cycle 3 and 4). Average heart rate was 1.6 beats/minute lower across the night on the HHCM compared to the LHCM (p=0.001). Conclusions The results of this study indicate that manipulation of body temperature during sleep may be a useful approach to enhance SWS sleep in postmenopausal women.