The current study investigated the prevalence of poor sleep quality and associated factors during the COVID-19 pandemic. We found that more than half of the population had poor sleep quality. Living alone, anxiety disorder, weight change during the pandemic, insufficient vitamin D scenario, and symptoms of COVID-19increased the chances of having sleep problems. The most affected PSQI subdomains were sleep latency, sleep disturbance, and sleep efficiency.
In Brazil, population studies have demonstrated high percentages of individuals with poor sleep quality, especially among women aged 40 to 50 years, without occupation, physically inactive, and with a greater number of health problems [15]. A national survey conducted in April 2012 with individuals from 132 different cities found that 76% of the population had at least one sleep complaint, indicating that approximately 108 million Brazilians may be affected by sleep disorders [16].
During the pandemic, several factors may contribute to altering the normal architecture of sleep, and population studies are important because they allow us to evaluate how the health outcomes affect the lives of the population.However, few studies with this methodology using the PSQI were conducted during the pandemic, which makes it difficult to compare the results. Our study, conducted from October to December 2020, found a higher prevalence than studies conducted at the beginning of the pandemic, as shown by Krishnamoorthy et al. (2020) in a systematic review, in which approximately 36% of the general population had poor sleep quality, and among healthcare workers, one of the most affected groups during the pandemic, 43% had poor sleep quality [17]. In Brazil, a study of 45,161 individuals from April to May 2020 showed that during the pandemic, 43.5% (95%CI 41.8;45.3) reported the onset of sleep problems and 48.0% (95%CI 45.6;50.5) had a previous sleep problem that worsened after the pandemic [15].However, it should be noted that this study was conducted online, which usually evaluates a more educated and higher-income group of the population and is different compared to the household survey.
During the pandemic, online tasks have made the workday never-ending and affect the quality of sleep. This work schedule can also reduce the sun exposure of individuals, an important factor since it is the main source of endogenous production of vitamin D [13]. We found that individuals with an insufficient vitamin D level were 47% more likely to have poor sleep quality. This association may be explained by the intracellular distribution of vitamin D receptors in areas of the brain that regulate the sleep-wake cycle or through pro-inflammatory mediators. Vitamin D is also involved in the production of melatonin, an essential hormone in the regulation of circadian rhythms and sleep. Melatonin synthesis is controlled by the active form of vitamin D (1,25(OH)D) from the enzyme tryptophan hydroxylase[18]. This suggests a possible role for vitamin D deficiency in sleep disturbances[19]. These results were found in a previous study with mining workers in the same region as this study;when evaluating sleep using the gold standard method, polysomnography, the workers with hypovitaminosis D had more sleep disturbances [20]. These workers had routines similar to confinement during the COVID-19 pandemic, since they were off-highway truck drivers and spent most of their time in machines inaccessible to sunlight[21].
An additional variable associated with poor sleep quality in our study was the weight change during the pandemic. Individuals who reduced up to 5.0% of their body weight during the pandemic had a 66% greater chance of having poor sleep quality, and those who gained 5.0% of their body weight had a 90% greater chance. Weight loss, when intentional, especially in obese individuals, can be of great use in improving sleep quality [22].However, unintentional weight loss may be related to increased physical and emotional stress, or food supply and demand. A systematic review conducted between July 2020 and February 2021, with 469,362 participants, found that during the pandemic, 11.1%-32.0% of individuals had experienced weight loss [23]. For some people, the lockdown provided more time to cook and eat better, butthe majority of people suffered from malnutrition and weight loss because of inflated food prices and food insecurity. In Brazil, more than half of the households (59.4%) were food insecure during the pandemic [24]. Not eating enough food of adequate quantity and quality has health impacts, such as poor mental health and increased likelihood of diseases [24],increasing the chances of poor sleep quality and higher vulnerability to COVID-19.
In addition, pandemic confinement was associated with weight gain in up to 7.2–72.4% of participants in a systematic review [23]. Excess weight interferes with sleep quality in several aspects, by anatomical factors such as airway obstruction, or by inflammatory factors such as increased cytokines, which can induce sleep disturbances by altering the sleep-wake rhythm[25]. Furthermore, there is a strong association that poor sleep quality may increase the risk of obesity, as demonstrated in longitudinal studies, such as in a cohort of 83,377 Americans, in which among men and women who were not obese at baseline, participants who reported less than five hours of sleep per night had an approximately 40% higher risk of developing obesity than those who reported seven to eight hours of sleep (for men, OR= 1.45, 95% CI: 1.06, 1.99; for women, OR= 1.37, 95% CI: 1.04, 1.79) [26].
Unfortunately, the fear and uncertainty caused by the pandemic, the threats to survival, among other things, are one of the main problems encountered during the pandemic and have greatly influenced the quality of life and mental health [2]. Of all the factors evaluated in our study, we found that anxiety and living alone were the most strongly associated with poor sleep.
Pandemic contexts and social isolation affect the population in many dimensions of living conditions and health status, particularly concerning the mental health component. In Brazil, 52.6% of Brazilians frequently reported feeling anxious or nervous [5]. Anxiety, especially generalized anxiety disorder, has been described as one of the most important consequences of sleep deprivation [27].A study during the first weeks of the lockdown in Italy found that lower sleep quality was directly related to days spent at home in confinement, with mental health playing an important role in mediating sleep quality [28]. A systematic review and meta-analysis of 345,270 participants from 39 countries found consistent results regarding the association between sleep quality and psychological distress. The corrected pooled estimated prevalence of sleep problems was 18% among the general population and was positively associated with anxiety (Fisher's z-score of 0.48; 95% CI: 0.41 to 0.54)[27].
Psychological impact during a pandemic period is common and expected, as demonstrated by Brooks et al. (2020), who evaluated previous epidemics.The main psychological stressors were duration of quarantine, fear of infection, feelings of frustration and annoyance, inadequate information about care for the disease, financial losses, and stigma associated with the disease[2].
In addition to the previously mentioned factors, we also found that participants who had the co-occurrence of two factors associated with poor sleep quality had an increased chance of having impaired sleep quality. These results are important because the social and health context caused by the pandemic makes many subjects vulnerable to the co-occurrence of factors that negatively interfere with sleep quality. In this context, vitamin D insufficiency and weight gain, for example, are very related factors that can occur simultaneously [13, 19]. Therefore, the co-occurrence of these factors can increase the chances of poor sleep quality, as we have shown. To the best of our knowledge, this is the first study to evaluate the co-occurence of factors associated with poor sleep quality during the COVID-19 pandemic.
Insufficient sleep directly impacts the immune system and exponentially increases the chances of illness. Thus, we found a high prevalence of poor sleep quality during the COVID-19 pandemic, with several associated factors.Sleep quality may have been influenced by the COVID-19 pandemic and the government actions taken to contain it. Brazil is one of the countries with the highest number of deaths and lowest percentage of the population vaccinated.
Sleep is an important factor to consider in a pandemic, given its interfaces with numerous other health conditions, as well as an improved immune response in the face of an opportunistic infection[7]. Thus, a health emergency such as the one we are experiencing should be accompanied by adequate social support programs to mitigate the psychological, social, and economic effects, promoting a better situation to face a troubled period such as this.
The main limitations of this study are the variables obtained by self-report, which can lead to underestimation of risk behaviors or overestimation of protective behaviors, due to differences in the perception of each individual about the pandemic and associated factors. However, the assessment of sleep quality needs to be performed subjectively, since it considers intrinsic factors to the individuals' perception of their sleep. Furthermore, the sample design brings robustness to the study and favors the analysis of the COVID-19 scenario in the two municipalities of the Iron Quadrangle region. Thus, this study allows us to evaluate the relationship between the quality of sleep and factors related to the pandemic, providing subsidies for decision making, in a chaotic socio-sanitary and epidemiological context, to reduce the worsening of health conditions.