Circadian rhythm of postural control, sleepiness and verticality perception in older adults.

ABSTRACT

INTRODUCTION: with ageing, the risk of falling increases. It has been reported that fall frequency may depend on the time of the day, suggesting a possible circadian rhythm of postural control. The objective was to test whether postural control in older adults followed a circadian rhythm. Then, in order to examine the possible functions involved in circadian variations in balance performances, circadian rhythm of sleepiness and vertical perception were also tested. METHODS: eight participants (70.7 ± 4.7 years) were included. Baseline circadian rhythm profile was assessed through continuous core temperature measurement. Static and dynamic balance, subjective sleepiness and fatigue, and verticality perception were measured at 200, 600, 1000, 1400, 1800 and 2200, on separate weeks in a random order. RESULTS: temperature followed a circadian rhythm, with lowest temperature occurring at 0350. Circadian rhythm was detected for the centre of pressure displacement length and velocity, in dynamic condition eyes closed, with lowest performances occurring at 1833 and 1659, respectively. Subjective sleepiness and fatigue also followed circadian rhythm with lowest sleepiness occurring at 1546 and 1550, for the Karolinska Sleeping Scale and the Visual Analogic Scale of fatigue, respectively. Finally, the vertical perception was not significantly following a circadian rhythm. CONCLUSION: older adults present a circadian rhythm of balance, in particular in more challenging conditions, and the lowest performances occurred in the late afternoon These circadian rhythms could explain some of the falls happening at this time in community-dwelling older adults.