Association between recovery of frailty state and the nonparametric rest-activity rhythm patterns in the elderly community-dwellers: A 6-month follow-up study during Covid-19 pandemic.

Reversibility of frailty in the elderly has been discussed comprehensively and but association between recovery of frail state and rest-activity rhythm (RAR) patterns remains unclear. The aim of the current study was to examine a predictor of RAR patterns at the baseline against change of frail state after the intervention in the elderly community-dwellers. This study was performed during Covid-19 pandemic, at the period from April in 2020 to March in 2022. Participants were publicly recruited from senior's exercise program hosted by Akita city or Yurihonjo city. The revised Japanese version of the Cardiovascular Health Study criteria (revised J-CHS criteria) was used to assess frail state in each participant before and after the 6-month intervention. To measure the nonparametric RAR parameters consisting of interdaily stability (IS), intra-daily variability (IV), relative amplitude (RA) and average physical activity for the most active 10-h span (M10) or for the least active 5-h span (L5) over the average 24-h profile, an Actiwatch Spectrum Plus device was worn on each participant's non-dominant wrist for seven continuous days. The final samples were 75 participants except for persons with uncompleted data, classified into the improved group (n = 12), the maintained group (n = 53) and the deteriorated group (n = 10) according to frail alteration after the six-month intervention. As a result of the multinomial logistic regression analysis with the reference of the maintained group, the improvement of frail state associated with a low value of IS and total night-sleep time at the baseline, and M10 and L5 at the initial time were also able to predict worsening of frail state after the six-months intervention. A result of this follow-up study provides grounds for our proposal that alterations of RAR patterns in the elderly could be observed in association with recovery or worsening of frail state after the intervention. The potential finding, however, warrants further longitudinal investigation.