To the best of our knowledge, this study was the first to investigate the effect of quarantine/lockdown due to the COVID-19 pandemic on sleep quality in Italian population subjects. The main results of our study are the worsening sleep quality, the increase in BMI and the reduction of physical activity after quarantine. Sleep quality was mostly worsened in subjects performing smart working compared to subjects not performing smart working in both genders. Males performing smart working had a significantly worse sleep quality than their female counterparts working in the same modality.
Study findings revealed that quarantine resulted in a worsening of sleep quality in normal weight and overweight subjects and in subjects with grade I and II obesity. In particular, there was an increase in sleep onset latency and sleep disturbance in both males and females. There was a significant worsening of sleep efficiency in females while there was a significant worsening of daytime dysfunction in males. There was an increase in BMI in normal weight and in subjects with grade I and II obesity after 40 days of quarantine. In addition, physical activity significantly decreased in all cohort of subjects. However, females had a trend toward the decrease of physical activity while males significantly decreased physical activity. As well known, on March 12th 2020 Italian people experienced locked down in order to reduce the widespread of the pandemic of coronavirus. As consequence, quarantine was associated to the interruption of work routine and these results in economic issues due to economic activity stalls and job losses mount. This generates worries about income, savings, and making ends meet. As a consequence of the lockdown, trips were canceled, and people were isolated from friends and family. Therefore, the isolation at home could generate the depression or exacerbate it in people that were already affected. Along with these situations, continuously hearing or reading about the pandemic without a break contributes to the onset of stress. As well known, stress is an adaptive response of the organism to real or perceived stressors. The main components of the stress system are the corticotropin-releasing hormone and locus coeruleus-norepinephrine/ autonomic systems that are connected to peripheral effectors such as the hypothalamic-pituitary-adrenal axis, and the limbs of the autonomic system . It has been reported that hypercortisolism can lead to fragmentation of sleep, decreased slow-wave sleep, and shortened sleep time. To complicate matters, sleep disturbances can in turn further worsen hypercortisolism and thereby worsening the cycle . Interestingly the worsening of sleep quality was more evident in subjects with normal weight and in subjects with grade I and II obesity. No further worsening was noticed in subjects with obesity grade III. This could be because subjects with obesity III grade had already a poor sleep quality at the baseline and there was not further worsening margin. As well known, the degree of obesity is directly correlated with sleep quality . Subjects with normal weight and obesity I and II grade experienced an increase of their BMI. This could be explained because they reduced physical activity. Indeed, the excess of adipose tissue narrows breath airways but it is also involved in the releases of cytokines . In particular IL-1, IL-6 and TNF-α are not only pro-inflammatory cytokines but also a ‘sleep-regulatory substances’ [21,38]. TNF-α and IL-1b, whose secretion follows a circadian rhythm, with the highest TNF-α and IL-6 secretion during the night (between 01:00 and 02:00 hours), are involved in the physiological regulation of sleep in both animals and humans , playing an important role in the slow-wave sleep . Interestingly males reported a decrease in physical activity. Accordingly, it has been reported that during quarantine outdoor activities and social activities are prohibited by the governments and this could result in a decrease of physical activity . Thus, a consequence of quarantine is limited physical activity that in turn results in an increased risk of developing obesity. On the contrary, previous studies reported that males are more active than females in leisure-time [42,43]. Indeed Martin- Gonzalez et al performed a study investigating the prevalence of physical activity during leisure time in adults from the 15 member states of the European Union and the relationship with socio demographic variables finding that a higher percentage of males practiced leisure-time physical activity . Similar results were found by Steptoe et al that carried out a survey in university students from 13 European countries (Belgium, England, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, The Netherlands, Poland, Portugal, and Spain) in 1990 and repeated in 2000 highlighting that the prevalence of leisure-time physical activity was higher in males . Another aspect to be considered regards the diet that is known to affect both body weight and sleep quality [4,44].
Evidence demonstrated that a higher energy intake notably from fat  and snacks , has been frequently reported in poor sleepers than in normal sleepers. NHANES data reported that poor sleepers compared to normal sleepers (7–8 hours of sleep/night) had a lower consumption of protein, fat, carbohydrate, and fiber . Clinical intervention studies have corroborated these evidences reporting that during sleep restriction fat was also highlighted as a macronutrient of choice in subjects with a normal habitual sleep [48,49]. Although studies reported that there is a relationship between sleep quality and diet these epidemiologic evidence cannot address causality or the direction of the relation among these variables. In fact, it is unknown whether it is dietary intake that affects or sleep quality, or viceversa. Relationship between dietary patterns and sleep quality were recently showed in a cross-sectional study . In this study, a high intake of fresh food like vegetables and fish, were associated with good sleep quality, whereas a high consumption of packaged and processed foods such as confectionary were associated with poor sleep quality, evaluated by a high global Pittsburgh Sleep Quality Index score . Also a poor sleep quality was evident in subjects who consumed sugar-sweetened beverages or energy drinks . In addition, other epidemiologic studies have found the relationship between diet and sleep quality [51–53], highlighting that both low and high intake of protein (<16% and >19% of energy from protein, respectively) were associated with poor sleep quality characterized by difficulty in maintaining sleep. Some foods, especially fresh ones, including fish, fruit, vegetables, and milk products have been identified as sleep-inducers; however, longer-term effects of dietary intake on sleep quality have not been examined in randomized controlled studies [4,44].
Even if not evaluated in this study, we hypothesize that a change in eating habits due to increased hunger and decreased satiety could contribute to weight gain observed in our studied population. Another important aspect to consider regarding diet is that during quarantine/lockdown, the individuals could have spent more time than usually happens in the kitchen for cook, with a consequent increase in the intake of carbohydrate, mostly pizza, homemade desserts and bread. In fact, as reported in the paragraph above, there is a bidirectional relationship between diet-obesity and sleep disturbance. Finally the house confinement imposed by quarantine could be associated to the decreased intake of fresh food, as fruit, vegetables and fish, all food rich in vitamins (including vitamin C, beta-carotene, and vitamin D), minerals (including selenium and zinc) and omega 3 fatty acids with anti-inflammatory and antioxidants activities. The low consumption of these micronutrients is associated with both obesity and sleep disturbance [54–56]; in particular, vitamin D plays a key role in the relationship between obesity and sleep disturbances [57–60].
Another interesting finding of our study is that smart working was associated to a greater deterioration of sleep quality that was more pronounced in males than females. This could be due to smart-device overuse and it is in agreement with a previous study carried out in 494 participants, from the three major cities in the United Arab Emirates finding that 81% of poor sleepers were heavy users of smart-devices thus concluding that poor sleep is strongly correlated with smart-device overuse . In particular, poor sleepers have been reported to be five times more likely to be overuses . Further, subjects in quarantine could be lead to check the news on phone, to join a virtual meeting with family or friends, to watch TV, or to stay at computer later in the evening thus resulting in a huge increase in screen time. Excess screen time, especially later in the evening, can have a detrimental impact on sleep. Not only it can stimulate the brain in ways that makes it hard to wind down, but the blue light from screens can suppress the natural production of melatonin, a hormone that is known to be the main key player of sleep [62,63].
Limits and Strengths
We are aware that there are some limitations in the current study. First, the main limitation of this study is represented by a self-reported weight after quarantine. However, other studies have carried out the same evaluation modality . Second, the sample size was relatively small. Nevertheless, we have calculated the sample size using 95% power. The number of cases required was 40, while we used 121 individuals i.e. more than double those required. Third, although it is well known that dietary intake are important determinants of both weight gain and sleep disturbance, we did not include in this study the diet analysis.
However, the strengths of this study are several. In particular, this study provide unique information regarding a particular social condition represented by quarantine during a pandemic. Nevertheless, a major strength of this study is the homogeneity of our sample population that further strengthens the power of the study. In particular we have adopted stringent exclusion criteria including clinical conditions which could interfere with sleep quality like neurological disorders, chronic metabolic and cardiovascular diseases, and smoking subjects, known factors that can affect both sleep quality and weight gain making it possible to compare the variables independently across subjects. In addition, all study individuals lived in the same geographical area, Naples metropolitan area (latitude 40°49′ N; elevation 17 m), likely with the similar nutrient availability and food consumption patterns, which allowed us to increase the homogeneity of the study sample. Furthermore, we included a variety of potential covariates, such gender and smart working, to minimize the effect of confounding factors on the role of quarantine/lockdown on sleep quality. An additional strength is the Pittsburg Sleep Quality Index questionnaire that was by phone administered and not self-reported in order to minimize any bias related to the filling of the questionnaire. To avoid inter-operator variability, only four expert nutritionists administered and calculated the Pittsburg Sleep Quality Index questionnaire and the telephone interview at the baseline and at the follow up.