INTRODUCTION

Inadequate diet and low physical activity are factors associated with the development of obesity in different age groups¹.

However, other factors are emerging that could be involved in the development of obesity, including sleep¹, which is important for growth, human development, metabolism, weight regulation, immune function, learning, memory and emotional health, so, studies in children and adolescents reveal that up to 70% of students sleep less than recommended for their age², despite the recommendation of the National Sleep Foundation to maintain between 7 and 9 hours of sleep per day in young adults and adults³.

In relation to the deficit in the quantity and quality of sleep, a highly vulnerable group is identified which corresponds to university students⁴. It should be noted that they have extensive academic conferences, concentration of the studies in the night, reduction of free time allocated to non-academic activities, high levels of stress. On the other hand, students at times have foods that are not recommended, particularly at night and high consumption of caffeine and energy drinks.

A reduction in sleep hours in university students has been associated with a decrease in academic performance, depression and can be detrimental to health⁵. Due to the academic demand and high intensity produced by the University, it is generally not possible to cover the recommended hours of sleep, therefore, students are expected to maintain habits, behaviors and a vulnerable and irregular meal schedule⁶.

Authors have suggested that through an unclear mechanism, lack of sleep, would affect cognitive processes, it has been suggested that certain stress-associated hormones that are secreted in conditions of sleep restriction can affect the physiology of neurons and contribute to the cognitive impairment⁷. These reflections might suggest that the consequences of exposure to poor sleep quality could be long-term.

Previous studies have reported concerning results in relation to the poor quality of sleep of university students, that is how in a group of medical students more than 30% presented poor and unsatisfactory sleep quality⁵. In another study conducted in nursing students, the prevalence of insomnia was also close to 30%⁸.

Other research in university students indicated that more than 92% of students reported poor sleep quality, while 77% of them reported a very irregular sleep schedule⁹.

It is important to point out that important researches have also related in university students the poor quality of sleep with an increase in overweight and obesity¹⁰, in addition, diverse studies have shown differences in the amount of sleep, insomnia and daytime somnolence while comparing sexes^11-12.

Due to the aforementioned, it is essential and relevant to continue investigating associations or consequences that involve deficits in the quantity and quality of sleep.

The objective of the present study is to compare sleep habits, insomnia and daytime sleepiness in university students according to anthropometrics measures.

MATERIAL AND METHODS

Cross-sectional study, all university students who were present at the time of the evaluation were included; and who expressed their informed consent through written documentation, excluded students who presented medical leave and did not sign the requested document.

For the sample calculation, the total number of Campus students (6,800), heterogeneity 50%, margin of error 3%, and confidence level of 95% were used, resulting in a total of 923 students as a minimum sample of the study. The questionnaires were self-administered at the time and later an anthropometric evaluation was carried out by a professional Nutritionist. Finally, there were 1,275 students from different careers at the San Sebastian University (Chile), who formed the study voluntarily, during the 2017 and 2018 academic years. Sleep quality was determined through the questionnaires: Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index and Insomnia Severity Index.

The study was developed according to the Declaration of Helsinki regarding work with human beings and previously approved by the Ethics Committee by Universidad San Sebastián.

RESULTS

The sample was represented by 1,275 university students (74% female); age, height, weight, and BMI were 21.7±2.4 years, 63.1±11.5kg, 163.4±8.3cm., 23.5±3.2kg/m² respectively (Table 1). 77.9% of university students sleep less than the recommended hours, without differences due to gender and nutritional status. The average daytime sleepiness score was slightly drowsy, a similar situation occurred with the average insomnia score (subclinical insomnia); students on average slept at midnight and sleep was 6.4 hours.

Table 2 shows the percentage of daytime sleepiness and insomnia according to sex, a high prevalence of daytime sleepiness (34.2%) and insomnia (68.5%) in college students, when comparing daytime sleepiness by sex higher in females (p=0.04). When comparing diurnal somnolence according to nutritional status, there are no significant differences; however, in insomnia, underweight and obese students are the ones with the highest levels of insomnia (p<0.001).

We performed the anthropometric comparison and sleep habits according to BMI classification (Table 3), there were differences in weight, BMI and waist among the 4 groups, with respect to insomnia it was observed that the low weight group presented the highest insomnia score that significantly contrasted with the normal weight group (p<0.05).

Figure 1 shows that obese women present significantly higher scores in daytime sleepiness than those with low weight and normal weight (p<0.01). Obesity in men presented significantly higher scores in daytime sleepiness than men with normal weight (p<0.05).

* ANOVA test, post hoc Bonferroni; p value <0.01.

Figure 1. Comparison of daytime sleepiness according to body mass index in women. 

Table 4 shows the results of the analysis between sleeping less than 7 hours of sleep and nutritional status, an association was found between a few hours of sleep with a higher BMI≥25 both in the crude and adjusted models (OR:1.36 (95%CI:1.059-1.751)), (OR:1.47 (95%CI:1.124-1.947)), (OR:1,12 (95%CI:1,01-1,991). There was also association with insomnia in models 2 and 3, no associations were observed with daytime sleepiness and physical activity, models 2 and 3 were adjusted for sex and tobacco consumption, performing an analysis with the BMI greater than 30 raw model (OR:1.469 (95%CI:1.033-1.897)) and model 2 (OR:1.557 (95%CI:1.021-2.823)) presented associations with less hours of sleep, this did not occur in model 3 where only a tendency was observed. (OR:1.305 (95%CI:0.988-1.756)).

DISCUSSION

The main result is that there is an association between fewer hours of sleep with a higher BMI and presence of insomnia in students. It also observed poor sleep quality of university students, translated into a high prevalence of insomnia in both sexes of university students and daytime sleepiness in women. In addition, when comparing nutritional status, obese women are those that present greater daytime sleepiness and the highest insomnia score was presented in underweight students.

Insomnia has numerous associated complications such as; poor sleep quality, anxiety, depression^16-17, and even affect memory and performance during the day, thus modifying student performance in university life¹⁸.

There are several factors that could influence these results, such as the large number of hours used in Internet use during the day, a strong correlation between Internet use and insomnia has been reported in the literature, affecting mainly men¹⁹.

In addition, a high caffeine intake has been significantly correlated with mild to severe symptoms of depression and insomnia, however in the present study no caffeine intake analysis was performed²⁰, because it was beyond the scope of the study.

Also, with the indiscriminate increase of the use of technology, even late at night, mainly cellular devices, a study in university students revealed a use of 60% of these during night time, with a significant relationship with insomnia, and consequent lack of energy, fatigue and headache²¹.

Another important result of the present study corresponds to the high prevalence of daytime sleepiness; in women, 36.7% were detected, while in men, 27.3% were observed, both mild and moderate drowsiness, thus revealing a significant difference according to sex. In addition, an association between female gender and BMI was found.

In a study of medical students, it was found that approximately 40% of them presented excessive daytime sleepiness, in addition the authors describe that the sleep quality of university students was deficient²².

That women with obesity presented a higher score on the daytime sleepiness scales is indicating that their quantity and quality sleep is not adequate; obesity may be accompanied by disorders ranging from snoring to apnea-hypopnea syndrome²³. Sleep disorders have increased over the last few years. University students, because they are constantly confronted with a condition of maintained stress, affect the quality of sleep in general, thus increasing anxiety which in turn is significantly associated with daytime sleepiness and insomnia¹⁷.

Interestingly, in the present study, low-weight students who present a higher prevalence of insomnia, possibly due to an overestimation as the group was very small (33 subjects), studies generally show that obesity is associated with insomnia²⁴, the obese university students were in second place in insomnia score.

Insomnia is a frequent condition in adolescents and young adults, especially in university students⁸. Frequently, insomnia is associated with the poor quality of sleep in college students, promoted by extensive days of night study, and irregular sleep hours. An interesting study in students of the Psychology Degree detected a close relationship between insomnia and academic performance, concluding that even failing was higher in students with insomnia²⁵.

Interestingly, in the present study, underweight students have a higher prevalence of insomnia, possibly due to an overestimation in the results, probably due to the low number of students who presented underweight (33 subjects). Studies generally show that obesity is associated with insomnia²⁴. Obese students ranked second in insomnia scores.

Although there are no significant differences, it is interesting to note that in daytime somnolence there was a trend in U-curve, although it did not reach a significant difference, and the students of greater weight slept less than normal weight students, but also did not reach a significant difference.

One study indicated that daytime somnolence is associated with a 3.5-fold increased likelihood of presenting common mental disorders (CMD), including anxiety, mood disorders and eating disorders, behaviors related to the aforementioned²⁶.

In addition, an investigation of 2,538 students found that 33.4% of them had MCT, and female students were more likely to develop MCT (39.2%) than males (24.4%)²⁷.

A recent university study provided evidence that the presence of more severe insomnia symptoms was associated with higher levels of suicidal ideation²⁸.

Although this study did not evaluate the association between sleep and obesity, several studies in children and adults have established an association between less sleep and increased risk of obesity, such as that performed in students of Nutrition and older Chilean subjects^29-30. Sleep exerts a wide range of physiological functions, a short duration of sleep is associated with a higher total caloric intake, greater fat intake, and lower protein intake, in addition there is limited evidence that associates short-term sleep with a lower intake of Fruits and vegetables, and lower quality diets³¹.

Among the strengths of the present study, it was emphasized that internationally validated surveys were used and these data can be compared with other studies. Regarding limitations, mention should be made of those of the study design (cross-section), so that causality can not be established and the data are not representative of all university students in the country.

CONCLUSIONS

Among the results of the study, there is an association between fewer hours of sleep with a higher BMI and presence of insomnia in students. The large number of university students who presented insomnia (in their different categories) in both sexes and excessive daytime sleepiness, revealed that it is the women who present this alteration more frequently and that the insomnia score is higher in underweight students. It is necessary that in Higher Education Institutions establish strategies to reduce sleep disorders, insomnia and daytime sleepiness, carrying out education on adequate sleep habits, since the alterations of these have consequences that affect the capacity of concentration and learning, academic performance, in addition to promoting alterations in nutritional status and unhealthy lifestyles, increasing the indirect risk of developing other chronic pathologies in university students.