JMIR Publications

ABSTRACT

Background:

This study aimed to investigate the relationships between adiposity and circadian rhythm, and compare the measurement of circadian rhythm using both actigraphy and a smartphone app that tracks human-smartphone interactions.

Objective:

We hypothesized that the app-based measurement may provide more comprehensive information, including light-sensitive melatonin secretion and social rhythm, and have stronger correlations with adiposity indicators.

Methods:

We enrolled a total of 78 participants (mean age: 41.5±9.9 years, 59% women) from both an obesity outpatient clinic and a workplace health promotion program. All participants (29 with obesity, 16 overweight, and 33 controls) were required to wear a wrist actigraphy device and install the Rhythm app for a minimum of four weeks. The Rhythm app estimates sleep and circadian rhythm indicators by tracking human-smartphone interactions, which corresponded to actigraphy. We examined the correlations between adiposity indices and sleep/circadian rhythm indicators, including sleep time, chronotype, and regularity of circadian rhythm, while controlling for physical activity level, age, and gender.

Results:

Among all sleep and circadian rhythm indicators, interdaily stability measured by either actigraphy or the Rhythm app had the strongest correlations with adiposity indicators such as body mass index, visceral adipose tissue, and body fat percentage. Although sleep onset and wake time measurements did not differ significantly between the app and actigraphy, our app-based measurement of circadian rhythm and sleep indicators were more consistent with previous research than actigraphy.

Conclusions:

Our findings suggested that regularity in the circadian rhythm, particularly measured via human-smartphone interactions, may be a promising target for obesity prevention.