Anti-COVID-19 measures threaten our healthy body weight: Changes in sleep and external synchronizers of circadian clocks during confinement

Abstract

Background & aims: Emergency measures in the face of the recent COVID-19 pandemic have been different among countries, although most have opted for confinement and restrictions on social contact. These measures have generated lifestyle changes with potential effects on individuals' health. The disturbances in daily routines due to confinement and remote work have impacted circadian rhythms and energy balance; however, the consequences of these disruptions have not been studied in depth. The objective was to evaluate the impact of 12-week confinement on body weight, considering changes in several external synchronizers of the biological clock.

Methods: The participants, 521 university students (16-35 years), responded to 52 questions oriented to determine light exposure, sleep patterns, sedentary lifestyle, and eating times.

Results: We found a reduction in sunlight exposure and sleep duration, an increment in sedentarism and screen exposure, and a delay in the timing of the main meals and sleep in the whole cohort. These behavioral changes were associated with a twofold increase in obesity. Subjects who increased their sedentary hours and shortened their sleep to a higher degree were those who gained more bodyweight. The most influential factors in body weight variation during confinement were sleep duration, physical activity (sedentarism), and light (timing of screen exposure). The mediation model explained 6% of the total body weight variation.

Conclusions: Results support a significant impact of confinement on several external synchronizers of the biological clock and on body weight. Health-related recommendations during the pandemic must include behavioral recommendations to mitigate the adverse effects on the biological clock.

Keywords: Biological clocks; Confinement; Covid-19; External synchronizer; Obesity.

Fig. 1

Sample collection chart.

Fig. 2

Variation of main outcomes. A) Variation of BMI, B) Variation of BMI classification and C) Variation of chronotype classification. A shows the mean, and the dispersion is expressed as the Standard Error of the Mean and the U-The Man Whitney test was used. For B and C comparison of proportions was used. ∗∗∗p < 0.001, ∗∗p < 0.01, ∗p < 0.05. BMI: Body mass index.

Fig. 3

Changes in external synchronizers with confinement. Y axis represents duration in Figure A and timing in Figure B. Mean (SEM). The U-The Man Whitney test was used. ∗∗∗p < 0.001, ∗∗p < 0.01, ∗p < 0.05, ns: not significant.

Fig. 4

External synchronizers and bodyweight variation during confinement. A) Sleep duration, B) Screen exposure time and C) Sedentarism. The capital letter represents the difference in the groups. Mean (SEM). The U-The Man Whitney test was used. ∗∗∗p < 0.001, ∗∗p < 0.01, ∗p < 0.05.

Fig. 5

Mediation models of external synchronizerson body weight variation. Body weight variation (BWV) as the dependent variable, Δ sleep duration, Δ sedentarism, Δ screen exposure time as independent variables. Δ was calculated by subtracting the variables from the thirteenth week to the first week of confinement. The straight arrows represent the correlation between variables of interest; the curved arrows denote the covariance among the three represented external synchronizers. The beta coefficients are shown in italic letter while beta coefficients of the adjusted model are shown in bold letter. Cov. = Covariance. BMI = Body Mass Index. Δ = Delta. ∗∗∗p < 0.001, ∗p < 0.05.

Fig. 6

Changes after twelve weeks of confinement on biological clock synchronizers. Sunlight exposure time and sleep duration decreased. Sedentarism, screen exposure time and body weight increased while meals timing and midpoint of sleep were delayed. All changes were statistically significant p < 0.05.