Assessing the Impact of Rotational and Shift Work on Sleep, Activity, Energy Balance, and Food Choice in Adults

Despite the rising evidence of harmful health effects from sleep disruption caused by shift employment, society relies on it. Shift work is a broad word that refers to any work schedule that is not between the hours of 8 a.m. and 4 p.m. This study considers three groups: 1) day workers - Including people working from 9 a.m. to 5 p.m./8 a.m. to 4 p.m. 2) shift workers - Including those involved in any arrangement of daily working hours other than the standard daylight hours 8 a.m. - 5 p.m 3) rotational workers - Including those who work on set schedule and working hours are rotating on a set schedule. This study will not include offshore workers. According to the International Agency for Research on Cancer (IARC), night shift work has been classified as Group 2A, probably carcinogenic to humans, based on sufficient evidence of cancer in animals and limited evidence in humans. Shift work affects humans in many ways, mainly by disturbing the body's circadian rhythm and sleep patterns. During the night, human bodies produce melatonin and maintains a constant stream of melatonin signals that leads to sound sleeping. However, working at night puts shift workers in a circadian misalignment due to melatonin suppression. With a disturbed circadian rhythm, the different systems in the body don't function optimally. A person can struggle to fall asleep, wake up during the night, or be unable to sleep as long as they want in the morning. Another significant side effect of shift work is altered meal timing and disturbed hormonal balance. The key regulators of satiety and hunger, the hormones Leptin and Ghrelin, respectively, are driven by body's biological clock. Ghrelin stimulates appetite and decreases after meals with a reverse diurnal pattern from Leptin. Usually, these hormones work in concert to regulate feeding with meal size and time. Previous laboratory studies examining the immediate effects of circadian misalignment have demonstrated decreased Leptin levels and post-meal suppression of Ghrelin. If these results are applied to general shift workers, this may promote weight gain because of an enhanced appetite for calorie-dense foods with eating at night. Therefore, night shift workers tend to have a higher body mass index (BMI) and waist-to-hip ratio than day shift workers. Multiple epidemiological studies controlling potential confounders suggest that exposure to shift work alone can contribute to increased body weight, BMI and a higher prevalence of obesity. A long-term consequence of shift work is an increased risk of type 2 diabetes. As a result of physiological maladaptation to eating at abnormal circadian times, metabolic syndrome develops over time. Both night and rotating shifts have been associated with an elevated risk of heart disease and ischemic stroke. However, shift work and circadian irregularities do not appear to be the only factors contributing to adverse heart health outcomes but also the psychological and psychosocial stress associated with shift work.

This study's primary objective is to compare the diet patterns of day workers, shift workers and rotational workers. Previous research has shown no significant differences in the daily caloric intake of shift workers against day workers. Night workers have an enhanced preference for high-fat foods. However, in most of these studies, food intake was measured subjectively using Food Frequency Questionnaires (FFQ) and self-reported food diaries. Subjective tools may lead to inaccurate conclusions. Objective measurement of food intake in shift workers in real-life situations is required instead of a laboratory-based shift work simulation study. The international recommendation for acceptable daily macronutrient distribution for carbohydrates is 45-65%; for fats and protein, figures are 20-35% and 10-35%, respectively. This study is interested in analyzing the adherence to the daily macronutrient distribution by shift, rotational and day workers and if shift workers can achieve the recommendation for a healthy diet. The hypothesis is that shift and rotational workers would have a reduced score for vegetable, fruit and fibre intake. This research aims to study the timings and duration of food intake in workers. These factors can potentially explain the high obesity rate in shift workers and the increased risk for chronic noncommunicable diseases. Another objective is to inter compare the food intake of every worker on a working day and on a non-working day. This study is interested in seeing the caloric intake difference between the rest days and work days, frequency of eating moments, energy distribution of meals, timing of eating, and fasting intervals of workers from different categories. Considering how all these factors impact metabolic parameters like glucose tolerance and energy metabolism, evaluating these specific dietary measures is crucial.

Stress is another major factor that can influence workers' eating patterns, while only a few studies have been done to assess the impact of stress on the eating habits of shift workers. A nurse's study showed that stress significantly predicts energy and saturated fat intake. Often shift workers use food as a coping strategy for dealing with negative mood states. The objective is to compare stress levels between different worker categories and relate them to eating habits respectively.

This is a feasibility study which means data collected from this study will help determine the sample size and other factors for a large-scale intervention trial in the working cohort of Newfoundland. No previous study has been done on Newfoundland workers. This study aims to inform the design and implementation of a fully-funded trial. Data collected from this study will be used for developing hypotheses and sample sizes for future studies.

Secondary objective is to compare sleep levels in different cohorts of workers. Sleep quality is very subjective, implying that it can have different meanings for different persons. To compare sleep quality in terms of sleep duration, sleep efficiency, sleep onset time, total elapsed bedtime, and total sleep time in day workers, shift workers, and rotational workers.

To measure if shift and rotational work have any impact on the physical activity of workers. To compare the physical activity levels of different workers in terms of light/sedentary, moderate and vigorous physical activity.

It also includes collecting data to know each participant's chronotype preference. To compare this with each participant's work schedule and see if chronotype-aligned work schedules are more beneficial. Measuring objectively and subjectively each participant's physical activity and sleep quality. SWEAT study is interested in comparing both parameters' similarity and variability in the subjective and objective data. Determining the relationship between shift and rotational work and the cardiometabolic disease risk factors through the parameters we are measuring.