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. 2020 Sep 18;15(9):e0238772.
doi: 10.1371/journal.pone.0238772. eCollection 2020.

Association between light exposure and metabolic syndrome in a rural Brazilian town

Ana Amélia Benedito-Silva  1 , Simon Evans  2 , Juliana Viana Mendes  1 , Juliana Castro  1 , Bruno da Silva B Gonçalves  1 , Francieli S Ruiz  2   3 , Felipe Beijamini  3   4 , Fabiana S Evangelista  1 , Homero Vallada  3 , Jose Eduardo Krieger  4 , Malcolm von Schantz  2 , Alexandre C Pereira  5 , Mario Pedrazzoli  1
Affiliations

Association between light exposure and metabolic syndrome in a rural Brazilian town

Ana Amélia Benedito-Silva et al. PLoS One. .

Abstract

Context: Metabolic syndrome (MetS) is a complex condition comprising a 'clustering' of components representing cardiometabolic risk factors for heart disease and diabetes; its prevalence rate is high and consequences serious. Evidence suggests that light exposure patterns and misalignment of circadian rhythms might contribute to MetS etiology by impacting energy metabolism and glucose regulation.

Objective: We hypothesised that individuals with MetS would show disrupted circadian and sleep parameters alongside differences in light exposure profiles. We investigated this using data from a cohort study in Brazil.

Methods: Data from 103 individuals from the Baependi Heart Cohort Study aged between 50 and 70 were analysed. Motor activity and light exposure were measured using wrist-worn actigraphy devices. Cardiometabolic data were used to calculate the number of MetS components present in each participant, and participants grouped as MetS/non-MetS according to standard guidelines. Between-group comparisons were made for the actigraphy measures; additionally, correlation analyses were conducted.

Results: Motor activity and circadian profiles showed no differences between groups. However, the MetS group presented lower light exposure during the day and higher light exposure at night. Correlation analyses, including all participants, showed that greater daytime light exposure and greater light exposure difference between day and night were associated with reduced MetS risk (a lower number of MetS components). Also, the light exposure difference between day and night correlated with body mass index across all participants.

Conclusions: The observed results suggest a direct association between light exposure and MetS which appears to not be attributable to disruptions in circadian activity rhythm nor to sleep parameters. This link between light exposure patterns and MetS risk could inform possible prevention strategies.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. 24-hour profiles of light exposure, separated by groups.
Data are represented in a double plot averaged across five days. The means (bold line) and standard error of the means (shadow) are presented for the MetS group (blue) and Non-MetS group (red).
Fig 2
Fig 2. 24-hour profiles of motor activity profiles, separated by groups.
Data are represented in a double plot averaged across five days. The means (bold line) and standard error of the means (shadow) are presented for the MetS group (blue) and Non-MetS group (red).
Fig 3
Fig 3. Scatterplot of BMI (body mass index) and normalised difference between diurnal and nocturnal light exposure.
Data are presented with points for the MetS group (blue) and Non-MetS group (red). Across the entire sample, a line has been drawn to facilitate the calculated correlation display.
See this image and copyright information in PMC

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Publication types

Grants and funding

This study was supported by awards from Fundação de Amparo à Pesquisa do Estado de São Paulo: 2013/17368-0 to ACP, 2007/58150-7 to JEK, 2010/51010-8 to MP; Conselho Nacional de Desenvolvimento Científico e Tecnológico: 400791/2015-5 to HPVF and MvS; Research Collaboration Fund of the Universities Global Partnership Network: RFC 2017 to SE and MP; Academy of Medical Sciences/Newton International Fellowship: NIF004\1030 to FRdS; Hospital Samaritano: 25.000.180.664/2011-35; and Institute of Advanced Studies of University of Surrey: 2018/19 to FB.