¹ Department of Physiology, Edo University Iyamho, Edo state, Nigeria;

² Department of Physiology, Ekiti State University, Nigeria;

³ Department of Physiology, Baze University, Nigeria;

⁴ Biomedical Sciences, Birmingham University, United Kingdom

Corresponding Author: M. J. Adeniyi, PhD, CPT., Environmental and Exercise Physiology (Chronobiology & Neurobiology) Unit, Department of Physiology, Edo University Iyamho, Edo state, Nigeria. Tel: +2348066796517; ORCHID- 0000-0003-4591-8870. E-mail: adeniyi.mayowa@edouniversity.edu.ng.

Running Title: HEALTH EFFECT OF NIGHT READING FREQUENCY PRIOR TO SEMESTER EXAMINATION

	ABSTRACT
	INTRODUCTION
	METHODOLOGY
	STATISTICAL ANALYSIS
	RESULTS
	DISCUSSION
	CONCLUSION
	CONFLICT OF INTEREST
	REFERENCES

	ABSTRACT

BACKGROUND: Night-time study is a routine practice exhibited by public university and college students in Nigeria most especially before and during end of semester examination period. AIM AND OBJECTIVES: We investigated the impact of pre-examination night-time study frequency on sleep pattern, peripheral oxygen saturation (SPO2) and anthropometrical indices in age-matched Nigerian female students. MATERIALS AND METHODS: 60 age-matched female subjects who emerged from simple random sampling were classed into irregular and regular night study groups using Visual Analogue Scale Questionnaire. Measurements of SPO2, pulse rate (PR), weight and height were done using pulse oximeter, weighing scale and meter rule respectively. Insomnia index (IN) and Day-time Sleepiness Indices (DS) were determined using sleep quality scale. RESULTS: Regular night-time study has no significant effect (P<0.05) on SPO2, PR and DS when compared with irregular night-time study group. However, students who reported regular night-time study exhibited significantly higher (P<0.05) IN, body weight and body mass index (BMI) when compared with irregular night-time study group. There was a positive correlation between IN and BMI (r=0.269, P<0.05). Pulse rate also negative correlated with SPO2 (r=-0.280, P<0.05) and BMI (r=-0.342, P<0.05). Pulse rate also negative correlated with SPO2 (r=-0.280, P<0.05) and BMI (r=-0.342, P<0.05). CONCLUSION: The results of the study indicated that female students undergoing regular night-time study prior to examination exhibited higher body weight, body mass index and insomnia index.

	INTRODUCTION

   Night is a period between sunset and sunrise. Naturally, diurnal organisms take their rest at nighttime (1-3). A natural state of rest existing in many multicellular organisms including human beings is known in popular consensus as sleep. Sleep plays a number of roles in physical, mental and emotional health, helping in conserving and restoring metabolic energy, protection and defense (4, 5). Nowadays, most especially, sequel to the advent of electric bulb centuries ago and due to population growth, busy schedule and socioeconomic reasons, there has been a rapid growth in the population of night workers and non-observers of nocturnal sleep (6, 7). For instance, a study by Trade Union Congress (TUC) in 2018 (8) indicated that the number of people who worked night shifts has increased by 5% since 2013, with women accounting for two-thirds (66.8%) of the increase in Europe. In United States, there was 11 percent increase in the number of night shift white collar workers between 1991 and 1997. In Nigeria, even though, there is no specific data on the actual population of night workers, report from National Bureau of Statistics (9) indicated an increase in national population from 170,157,060 in 2012 to 193,392,51 in 2016.

   Night workers include essential health workers, security officers and other employment arrangements that provide services round the clock (10). Another example of night active worker are college and university students. Studies that examined the effect of night class on students’ health have documented memory loss culminating in poor academic outcome, muscle ache, confusion, mood swing, perturbation in stress hormone levels and high blood pressure (11). Majority of these symptoms were related to sleep deprivation, an inability to undergo sufficient sleep. A study that investigated the prevalence of disease-unrelated sleep deprivation among college students indicated that 27% of students were at risk of insomnia with a wide discrepancy between weekday and weekend sleep durations and a notable variation along racial line (12).

   Although there are insufficient data that demonstrate the nature of association between night-time class and obesity in age-matched students, Buxton et al., (13) reported that short and long sleep durations were associated with increased body mass index. Calamaro et al., (14) found no association between sleep duration and obesity. Instead, conditions such as depression, night-time physical activity were found to correlate with obesity (15). Other studies claimed that there was an inverse association between short sleep duration and body mass index (11, 16).

   End of semester examination is an example of summative assessment, which aims at evaluating students’ academic performance towards the conclusion of an instructional unit (17). In most of the public educational institutions in Nigeria, this form of evaluation is not only common but also attract more points than the continuous assessments which is formative in nature (18). Consequently, change in students’ psychology occurs towards the examination time. An example of such is increase in academic attitude evidenced by increase in frequency of night study. Unfortunately, there is no sufficient information on the effect of pre-examination night study frequency on sleep pattern, anthropometric indices and peripheral oxygen saturation in age-matched female students. Therefore, the aim of the study was to investigate the impact of night-time study frequency on sleep pattern, anthropometrical indices and peripheral oxygen saturation (SPO2) in age-matched female students before examination.

	METHODOLOGY

   Site of the Study

   The work was carried out in Edo University Iyamho, Etsako West Local Government Area, in Edo State. The area was chosen based on the fact that no similar study has been done in the area.

   Participants

   The study was conducted on 60 adult female university students prior to their first semester examination. The subjects were in the first semester of their second year in the university. They were categorized into irregular and regular night study groups of 30 subjects each.

   Inclusion Criteria

   90 adult female university students averaging 18.42 ± 0.22401 years were accommodated into the groups respectively. Ethical clearance was obtained from the Ethics and Research Committee, Department of Physiology. Written consent was gotten from each subject and a well-structured questionnaire was administered to rule out those with medical history of respiratory diseases, cardiovascular diseases, metabolic diseases or anatomical deformities. Students who report their aversion to night study were not accommodated into the groups.

   Physical examinations were also done and those that were not medically fit were disqualified. After the screening, 60 female subjects were drawn out and were categorized using Visual Analogue Scale Questionnaire into two groups; irregular night study group and regular night study group. Students that score 25% and below were classified as irregular night-time study group, while those that score above 25% were classified as regular night-time study group.

   Determination of Night Activity Frequency, Insomnia Index and Day-time Sleepiness Index

   Visual analogue scale questionnaire was used to evaluate students’ night activity frequency. Insomnia index and day-time sleepiness index were assessed using Sleep Quality Scale developed according to the method of Yi et al., (19).

   Evaluation of Peripheral Oxygen Saturation, Pulse Rate and Anthropometric Indices

   Peripheral oxygen saturation and pulse rate were measured in sitting posture after five minutes of rest using pulse oximeter model: MD300C25.

   With the aid of weighing scale (Hanson China) and meter rule, body weight and height were determined respectively.

   Body mass index was calculated using (Weight (Kg)/Height2 (m²).

	STATISTICAL ANALYSIS

   All data were expressed as mean ± standard error of the mean (SEM) using IBM SPSS 21.0. Statistically significant differences were accepted at p<0.05. Comparisons were done using student T Test.

	RESULTS

   Effect of Night study frequency on Insomnia index and Day-time Sleepiness index

   The result shown in Figure 1A indicated a significant increase (P<0.05) in insomnia index between regular night-time study group and irregular night-time study group.

   The result shown Figure 1B indicated no significant difference on Day-time Sleepiness Index between regular night-time study and irregular night-time study group.

   Effect of night study frequency on SPO2

   The result shown in Figure 2 indicated no significant difference on SPO2 between regular night-time study and irregular night-time study group.

   Effect of night study frequency on anthropometric indices

   The result shown in Table 1 showed that regular night-time study significantly (P<0.05) increased body weight when compared with irregular night-time group. Regular night-time study significantly (P<0.05) increased BMI when compared with irregular night-time group. Regular night-time study had no significant effect on age or height.

   Effect of night study frequency on pulse rate

   The result shown in Figure 3 showed that regular night-time study had no significantly (P<0.05) effect on pulse rate when compared with irregular night-time study group.

   Correlational analysis between SPO2, pulse rate and anthropometrical and indices

   The result shown in Table 2 showed that pulse rate negatively correlated with SPO2 and BMI (P<0.05. Insomnia positively correlated with BMI and age (P<0.05). There was a positive correlation between pulse rate and height (P<0.05).

View larger version : [in a new window] Figure 1. A, Effect of night study frequency on insomnia index. *Significance difference from irregular night-time group at P<0.05; B, Effect of night study frequency on day-time sleepiness index. *P<0.05 from irregular group.

 

View larger version : [in a new window] Figure 2. Effect of night study frequency on SPO2. *P<0.05 from irregular group.

 

View larger version : [in a new window] Figure 3. Effect of night study frequency on pulse rate. *P<0.05 from irregular group.

	DISCUSSION

   Insomnia is defined as a delay in sleep onset (20). Like previous study (11), the present study reported that increase in the frequency of night-time study resulted in high insomnia index. Night-time study-induced insomnia represented disruption of sleep/wakefulness cycle and might be due to disruption of melatonin rhythm (2). Melatonin level is known to increase in the night or dark period (sleeping time) and hence plays major role in circadian sleep (2). As light suppresses melatonin secretion through inhibition of arylalkylamine N acetyltransferase (ANAT), reading at night-time results in suppression of melatonin synthesis and sleeping difficulty (21, 22). The present study showed that insomnia index was positively correlative with age; suggesting that high insomnia index occurred in older female students. Subjects who experience insomnia sometimes reports episode of day-time sleep (6). However, as far as our work was concerned, students with frequent night-time study exhibited insignificantly high day-time sleepiness index. It is possible that the insignificantly high day-time sleepiness index be due to habituation. Habituation is a repetitive practice that results in re-entrainment of circadian rhythms. Evidence from shift work studies also indicated that women who were on regular work schedule were associated with less health illness than those who were on rotatory work schedule (2).

   Another consequence of night-time study is perturbation in BMI (23). Usually increase in BMI in adult connotes an increase in body weight, a modifiable factor (24). The study showed that regular night-time study elevated body weight and BMI. Many factors may account for the weight change and increased BMI. One of them is perturbation in nocturnal leptin secretion. Leptin is a hormone that regulates body weight and it is secreted more nocturnally (2, 25). A study has claimed that night activity suppresses the nocturnal level of leptin hormone (25) culminating in increase in weight gain and BMI. The finding of the work also indicated that BMI correlated positively with subjective insomnia index in the female students. This implied that female students with high BMI demonstrated high tendency for insomnia.

   Peripheral oxygen saturation (SPO2) is used to examine the extent of oxygenation of the peripheral tissue. The study showed that regular night-time study caused no significant effect on peripheral oxygen saturation. However, a significant negative correlation between SPO2 and pulse rate was observed in female students. Early report by Chinawa et al., (26) showed an inverse correlation between SPO2 and pulse rate in children. As far as the present study was concerned, we are aware that in addition to cardiac output, several other factors, most especially muscle mass and capillary density may affect SPO2. Nevertheless, the negative association implied that heart rate, a determinant of cardiac output is not directly related with peripheral tissue oxygenation in the female students; invariably, an increase in cardiac might not depict an increase in SPO2.

   Like SPO2, regular night-time study had no effect on pulse rate but pulse rate showed a significant positive correlation with height in the female students. This implied that higher pulse rate was observed in taller female students. Furthermore, in popular consensus, obese subjects are known to exhibit higher pulse rate due to their higher metabolic rate. The significant negative correlation between pulse rate and body mass index (BMI) indicated the deleterious effect of night-time study on cardiac chronotropy.

   As regards the present study, increases in insomnia index, body weight and body mass index observed in students who undergo regular night-time study prior to summation assessment indicated poor health indices and susceptibility to adverse health consequences such as obesity, type II diabetes and cardiometabolic syndrome. Therefore, the result of the study highlighted the need for aggressive health education and policies which will guide students in the path of wellness and safety prior to end of semester examination period or any other forms of summative assessment.

	CONCLUSION

   The results of the study showed that female students undergoing regular night-time study prior to examination exhibited higher body weight, body mass index and insomnia index.

	CONFLICT OF INTEREST

   None declared by the authors.

	REFERENCES

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