Associação do jetlag social e do cronotipo com o consumo alimentar e ganho de peso durante a gestação: estudo de coorte prospectivo

Abstract

Introduction: The incompatibility between circadian and social clocks leads to circadian misalignment, which has been widely measured by social jetlag (SJL). Studies have associated SJL with nutritional diseases such as obesity, but this topic has not yet been studied in pregnant women. The chronotype, which concerns the inter-individual differences in phase allocation of circadian rhythms, is one of the factors that has been associated with circadian misalignment and also with nutritional diseases. However, the effects of the chronotype on food intake and weight gain during pregnancy were also not addressed in the literature. Objective: This thesis had two main objectives: 1) to identify the occurrence of SJL during pregnancy and to describe the effect of pre-pregnancy body weight on SJL throughout pregnancy; 2) to analyse the association of the chronotype with food consumption and weight gain during pregnancy. Material and Methods: The first phase of the study was carried out with 205 pregnant women in the first trimester. Thereafter, 100 pregnant women were followed up through a prospective cohort study in the second and third gestational trimesters. The SJL was calculated based on the absolute difference between the midpoint of sleep on working days and free days. Food intake was assessed by three 24-hour food records in each trimesters, totaling nine records. The intake and distribution of energy and macronutrients were assessed at meals throughout the day and the quality of the diet was assessed by the Revised Diet Quality Index (IQD-R). The chronotype was derived from the midpoint of sleep on free days (MSF) corrected for sleep output and the scores obtained were categorized into tertiles. The pre-gestational body mass index (BMI) (kg/ m²) and the current BMI (kg/ m²) were calculated. The Institute of Medicine recommendations were used to assess the adequacy of weight gain. Linear and logistic regression and the Generalized Estimation Equations (GEE) adjusted for confounding factors were used to determine the association between SJL and gestational trimesters (time) and anthropometric variables. In addition, GEE were used to determine the effects of chronotype and gestational trimesters on dietary patterns, daily energy, macronutrient distribution and weight gain. Results: Most pregnant women (54.5%) had SJL > 1h in the first trimester of pregnancy. A positive association was found between SJL and pre-pregnancy BMI in the third trimester (β = 0.200, p = 0.046). In addition, GEE analyzes showed that pregnant women with normal pre-gestational weight showed a decrease in SJL from the second to the third trimester (1.29 ± 0.11 and 0.93 ± 0.08, respectively, p = 0.032), but this was not found in the other groups of nutritional status (underweight, overweight and obesity). In addition, we found an isolated effect of the trimester of gestation on the SJL average. In this sense, pregnant women showed a decrease in SJL from the second to the third trimester (1.33 ± 0.08 versus 1.12 ± 0.07, respectively; p = 0.012). Regarding the results related to the chronotype, pregnant women with MSF values with a tendency to evening had breakfast later and also had a higher intake of energy and carbohydrates at dinner, compared to those with a tendency to morning. Pregnant women with a tendency to maturity showed a better quality diet in the group of milk and derivatives and saturated fat evaluated by the IQD-R. In addition, despite the tendency of pregnant women of all tertiles to gain excess weight during pregnancy, it was observed that pregnant women with a tendency to evening had a worse adequacy of gestational weight gain in the third trimester when compared to pregnant women with a tendency to maturity (2.24 ± 0.25 kg versus 1.22 ± 0.14 kg, p <0.001). Conclusion: SJL > 1h is quite prevalent during pregnancy and pre-gestational excess weight seems to lead to a greater risk of having SJL > 1h during pregnancy. In addition, pregnant women with a tendency to evening eat breakfast later and also have a higher intake of energy and carbohydrates at night, in addition to having a worse pattern of gestational weight gain in the third trimester. Our results emphasize the importance of considering chronobiological variables in prenatal nutritional guidelines to promote maternal and fetal health.