Consistency index of daily activity pattern and its correlations with subjective ratings of QOL

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ORIGINAL ARTICLE

Consistency index of daily activity pattern and its correlations with subjective ratings of QOL Ryota Amano1 · Akihiro Karashima2 · Ikuko Motoike1,3 · Norihiro Katayama1 · Kengo Kinoshita1,3 · Mitsuyuki Nakao1  Received: 29 May 2019 / Accepted: 24 April 2020 © Japanese Society of Sleep Research 2020

Abstract Since sleep is under circadian and homeostatic regulation, the status of regulatory mechanisms can be known from daily activity patterns, including both sleep and wake states. Therefore, the relationship between their quantitative characterization and associated subjective QOL can be expected to provide practical knowledge for maintaining/improving QOL. An index quantifying the consistency of daily activity patterns over days, the activity consistency index (ACI), was developed, and its correlations with subjective QOL ratings based on the Pittsburgh sleep quality index (PSQI) and the Kessler Psychological Distress Scale (K6) were analyzed using actigraphy data obtained from university students and IT workers. The consistency of the parametrically transformed actigraphy data was quantified using a parameter set tuned to optimize an ensemble correlation between the consistency measure and QOL. Comparisons of ACI with a previously proposed index (SRI: sleep regularity index) were made according to their correlations with the participants’ subjective ratings of QOL. The comparison of ACI and SRI with respect to the various quantitative features of daily activity revealed that ACI tuned to PSQI was correlated only with mean sleep-onset time and mean sleep duration, while SRI was correlated with most of the quantitative features of sleep. In addition, the correlation profile showed gender dependency. For male and female subjects in their 20 s, the analysis indicated a significant correlation between PSQI and ACI, but not between PSQI and SRI. ACI was shown to work well as an index of daily activity patterns relevant to subjective sleep quality. This ability suggests that ACI could be a basis for predicting subjective sleep quality. Through evaluating daily activity patterns using ACI, an individual may be able to select an appropriate lifestyle for maintaining/improving QOL. Keywords  Actigraphy · Subjective sleep quality · PSQI · K6 · Activity consistency index · Sleep regularity index

Introduction Sleep quality is undeniably one of the major determinants of quality of life (QOL). In humans, irregular sleep habits and lack of sleep are known to adversely affect mood, and physical and intellectual performance [1], and even lead to pathological states such as diabetes, obesity [2, 3], and psychiatric * Mitsuyuki Nakao [email protected] 1



Graduate School of Information Sciences, Tohoku University, 6‑6‑05 Aramaki Aza Aoba, Aoba‑ku, Sendai 980‑8579, Japan

2



Tohoku Institute of Technology, 35‑1 Yagiyama Kasumi‑cho, Taihaku‑ku, Sendai, Sendai 982‑8577, Japan

3

Tohoku University Tohoku Medical Megabank Organization, 2‑1 Seiryo‑machi, Aoba‑ku, Sendai 980‑8573, Japan



disorders [4]. Co