Blunted rest-activity rhythms link to higher body mass index and inflammatory markers in children

Abstract

Study objectives: Disturbances of rest-activity rhythms are associated with higher body mass index (BMI) in adults. Whether such relationship exists in children is unclear. We aimed to examine cross-sectional associations of rest-activity rhythm characteristics with BMI z-score and obesity-related inflammatory markers in school-age children.

Methods: Participants included 411 healthy children (mean ± SD age 10.1 ± 1.3 years, 50.8% girls) from a Mediterranean area of Spain who wore wrist accelerometers for 7 consecutive days. Metrics of rest-activity rhythm were derived using both parametric and nonparametric approaches. Obesity-related inflammatory markers were measured in saliva (n = 121).

Results: In a multivariable-adjusted model, higher BMI z-score is associated with less robust 24-h rest-activity rhythms as represented by lower relative amplitude (-0.16 [95% CI -0.29, -0.02] per SD, p = 0.02). The association between BMI z-score and relative amplitude persisted with additional adjustment for sleep duration, and attenuated after adjustment for daytime activity level. Less robust rest-activity rhythms were related to increased levels of several salivary pro-inflammatory markers, including C-reactive protein, which is inversely associated with relative amplitude (-32.6% [-47.8%, -12.9%] per SD), independently of BMI z-score, sleep duration, and daytime activity level.

Conclusion: Blunted rest-activity rhythms are associated with higher BMI z-score and salivary pro-inflammatory markers already at an early age. The association with BMI z-score seem to be independent of sleep duration, and those with pro-inflammatory markers further independent of BMI z-score and daytime activity. Novel intervention targets at an early age based on improving the strength of rest-activity rhythms may help to prevent childhood obesity and related inflammation.

Clinical trials registration: NCT02895282.

Keywords: activity rhythm; body mass index; inflammation; rest; school-aged children.

© Sleep Research Society 2020. Published by Oxford University Press on behalf of the Sleep Research Society. All rights reserved. For permissions, please e-mail journals.permissions@oup.com.

Figures

Figure 1.

Representative example of 7-day average actigraphs of several individual cases with high and low BMI z-score, C-reactive protein (CRP) and interleukin 8 (IL8). (A) represents an obese child (code 470; BMI z-score = 3.04) with a low relative amplitude (RA = 0.69) and a high fragmentation (intradaily variability = 1.01). (B) Represents a normal weight child (code 304; BMI z-score = 1.20) with a high relative amplitude (RA = 0.87) and low fragmentation (intradaily variability = 0.71). (C) represents a child (code 405) with a high C-reactive protein (CRP = 14.46 ng/mL) and a low relative amplitude (RA = 0.73). (D) represents to a child (code 422) with a low C-reactive protein (CRP = 0.17 ng/mL) and a high relative amplitude (RA = 0.88). (E) represents a child (code 455) with a high interleukin 8 (IL8 = 66.02 pg/mL) and a later L5 midpoint (05:37 am). (F) represents a child (code 416) with a low interleukin 8 (IL8 = 8.33 pg/mL) and an early L5 midpoint (01:07 am). The arrow represents L5 midpoint in (E) and (F).