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Arquivos de Neuro-Psiquiatria

Print version ISSN 0004-282X

Arq. Neuro-Psiquiatr. vol.68 no.5 São Paulo Oct. 2010 



Quality of sleep among university students: effects of nighttime computer and television use


Qualidade do sono entre universitários: os efeitos da utilização do computador e televisão no período da noite



Gema MesquitaI; Rubens ReimãoII

IMSc. Psychologist, Department of Child and Adolescent Health, School of Medical Sciences, UNICAMP. University of José do Rosario Vellano (UNIFENAS), Alfenas MG, Brazil
IIMD, PhD. Pediatric Neurologist, Division of Clinical Neurology, Hospital das Clinicas, FMUSP





This descriptive, cross-sectional study was based on subjective questionnaires that assessed nighttime habits of television viewing and Internet use during weekdays and perceived sleep quality among university students. Sleep perception was measured using the Pittsburgh Sleep Quality Index (PSQI). The study group comprised 710 university students aged 17-25 years. Analysis of sleep perception in relation to internet use revealed that 58.06% of subjects who accessed the internet between 19:00 and 21:00 slept poorly; 71.43% between 19:00 and 22:00; 73.33% between 19:00 and 24:00; and 52.38% between 19:00 and 03:00 (p=0.0251). Concerning the relationship between television exposure and perceived sleep, the groups did not differ from each other (p=0.9303). This study showed that internet use between 19:00 and 24:00 increases the risk of poor sleep among young adults, in comparison with television viewing times.

Key words: quality of sleep, internet, television, sleep disturbances.


Este estudo transversal descritivo com base em questionários subjetivos avalia o hábito de assistir TV e acessar a internet durante as noites nos dias de semana e a percepção da qualidade do sono entre universitários. Para avaliar a percepção do sono foi aplicado o Índice de Qualidade do Sono de Pittsburgh. O grupo estudado incluiu 710 universitários entre 17-25 anos. Para as análises da percepção do sono relacionado ao hábito de acessar o computador observou-se que acessam a internet e dormem mal: 58,06% entre as 19 e as 21h; 71,43% entre as 19 e as 22h; 73,33% entre as 19 e as 24h; 52,38% entre as 19 e as 3h (p=0,0251). Em relação aos horários de assistir TV e a percepção do sono os grupos não se diferenciaram entre si (p=0,9303). O estudo demonstra que acessar a internet durante os horários das 19 às 24h aumenta as chances dos jovens dormirem mal quando comparado aos horários de assistir TV.

Palavras-chave: qualidade do sono, internet, televisão, distúrbios do sono.



The effects of excessive use of electronic media, such as computers and television, have been identified as a health issue1-3. The implications of heavy nocturnal use of such media, particularly computers, remain largely unknown4.

Evidence shows that many young individuals surf the internet or watch TV programs in a habitual manner, often leading to impaired sleep quality2,5.

However, television programs and computers with internet access are clearly excellent means of communication and production. These technologies have had a radical effect on the social transformation process and have led to rapidly shifting paradigms that have had an impact on daily routines and habits7,8.

Although television and computers are similar in terms of intensity of light displayed, they differ in how they are used. When in front of the television, viewers usually sit or lie down in a comfortable position around three meters from the screen, changing channels with a remote control. However, in front of a computer monitor, internet users sit between fifty and seventy centimeters away from the screen and interact more actively with the device, engaging both mental and physical faculties to operate the equipment.

The use of these devices at inappropriate times, coupled with the brightness of the light that they project onto the retina, are factors that are thought to trigger changes in sleep patterns1,2,4. In the case of computer displays, the light that they emitted is in close proximity to the retina. According to Guyton, light-stimulated retina cells transmit electrical signals to the hypothalamus10. In addition to controlling the glands of the body, the hypothalamus contains a small nucleus that houses the biological clock, which is essential for regulating sleep/wake cycles and rhythms10. The strength, variation and timing of light projected onto the retina by these devices disrupt the normal release of melatonin in the body (the hormone that controls sleep), resulting in changes in quality of sleep11-13. Given that sleep plays an essential role in restoring energies expended during the day, and in memorization, concentration and learning processes14,15, the ramifications of sleep quality among young graduates undergoing academic and professional training are manifold.

Surveys have shown16,17 that internet users spend excessive time at the computer, and have found that the population as a whole is sleeping less hours due to exposure to television programs and computers on the internet1-3.

Against this background, the aim of the present study was to identify possible relationships between time spent using the computer or television, and sleep quality among young university students.



A descriptive, cross-sectional study was conducted, in which data on sleep quality was collected from a sample of 1,978 university students at a pubic university in the south of the state of Minas Gerais, Brazil. The random sample comprised 710 subjects, containing both women (486) and men (224). Their mean age was 20.7 years (standard deviation of 1.8 years), with a minimum age of 17.01 years, median age of 21.0 years and maximum age of 25.0 years.


The participants were asked to answer an objective self-assessment questionnaire on the use of television and the computer on weekdays during the following time periods: [A] 19:00 to 21:00; [B] 19:00 to 22:00; [C] 19:00 to 24:00; [D] 19:00 to 3:00.

Sleep perception was measured using the Pittsburgh Sleep Quality Index (PSQI). This scale is used to quantify the quality of sleep over the past month. It was devised to provide a standardized measurement of sleep quality18. The scale is straightforward and consists of 19 self-assessed items grouped into seven components weighted 0 to 3. The overall score ranges from 0 to 21, with lower scores indicating better quality of sleep. Individuals scoring less than five are considered good sleepers (GoodS), while those scoring more than five are rated as poor sleepers (PoorS). An overall score >5 on the PSQI indicates serious problems relating to at least two components, or moderate difficulties relating to more than three components. The PSQI instrument has been validated as reliable for use in Brazil19, and has been used in a number of studies in other countries20,21.

Inclusion criteria

Students drawn from the Federal University of Alfenas who were present in the classroom at the time of questionnaire application, and who agreed to take part on a voluntary basis by signing the informed consent form, were included in the study.


Data were collected in groups from the classrooms between August and November 2007. Contact with students was brief. The participating students were informed of the purpose of the study and the methods to be used and signed an informed consent statement.

The project "Life Habits and Sleep Complaints among Young University Students", on which the present study was based, was approved and homologated at the General Meeting of the Research Ethics Committee of the School of Medical Sciences of UNICAMP on October 24, 2006, under CAAE file no. 0441.0.146.000-06.

Statistical methodology

The data obtained in the study were tabulated, organized and stored in an electronic Excel spreadsheet. The compiled data were submitted to statistical analysis by the Research Board of the School of Medical Sciences of UNICAMP, using version 9.1.3 of the SAS (Statistical Analysis System) for Windows Service Pack 3 (SAS Institute Inc, 2002-2003, Cary, NC, USA).

The descriptive analysis was performed based on position and dispersion measurements for continuous variables, and frequency tables for categorical variables.

The following tests were used in comparative analyses: chi-square (χ2) and Fisher's tests to investigate associations and compare proportions; Mann-Whitney test to compare continuous or ordinal measurements between pairs of groups, and the Kruskal-Wallis test for comparisons among three or more groups; and multiple logistic regression analysis to identify factors impacting on sleep quality22. The significance level used for the statistical tests was set at 5%.



The overall PSQI scores for the 710 participants were: mean 6.5; standard deviation 2.6; minimum 0.0; median 6.0; and maximum 6.0. A total of 39.72% of respondents were found to be good sleepers and 60.38% were poor sleepers. Computer use was significantly higher among women between 19:00 and 21:00, and among men between 19:00 and 3:00 (p<0.0001; χ2). A significantly higher proportion of women reported watching TV between 19:00 and 21:00 than of men (p<0.0001; χ2) (Table 1).

No difference was found in any of the items of the Pittsburgh Sleep Quality Index between the groups, in terms of gender or perceived sleep. On the scale, 60.91% of the women reported poor sleep versus 58.93% of the men. The chi-square test was used: χ2 p=0.6169. A mean overall score of 6.5 was found for the women, and 6.3 for the men (p=0.2981; Mann-Whitney).

The mean perceived sleep scores for the different time periods of computer use were 6.3 (19:00 to 21:00); 6.6 (19:00 to 22:00); 7.0 (19:00 to 24:00) and 6.4 (19:00 to 3:00) (Table 2). Application of the Kruskal-Wallis test (p=0.3257) showed that there were no differences between the groups relating to time period.

The mean perceived sleep scores in relation to television viewing periods were 6.7 (19:00 to 21:00); 6.6 (19:00 to 22:00); 6.3 (19:00 to 24:00); and 6.7 (19:00 to 03:00) (Table 3). Application of the Kruskal-Wallis test (p=0.3257) showed that there were no differences between the groups (Table 4).




The findings from this study revealed that there were significantly higher numbers of poor sleepers among individuals using computers between 19:00 and 22:00 or between 19:00 and 24:00 (Table 2). In contrast, no significant differences in the numbers of poor sleepers were seen among television users between the different time periods (Table 3). This result is of particular relevance given that computer use at these times is prevalent not only in the student population but also among children, adolescents, adults and the elderly1-4,16,17.

To our knowledge, only seven studies investigating the impact of computer use on sleep patterns have been published in the worldwide literature1-4,16,17,23. All of these studies except one23 found that computer use disturbed sleep patterns.

In the present study, significant numbers of complaints of reduced sleeping times and increased sleep disturbances (Sleep Duration and Sleep Disorders components of Tables 2 and 3) were associated with media use, thus corroborating the results of previous studies1-3,23.

Our analysis showed that computer use (Table 2) was connected with a significantly higher risk of perceiving poor sleep quality among these university students, in contrast to the habit of watching television (Table 3). Our results are similar to those of Dworak17 and Van Den3, who reported a significantly higher risk of impaired sleep patterns following internet use before going to sleep than in relation to television use, among children and adolescents.

Furthermore, a study by Suganuma1 on the use of electronic media (television and computers) in relation to perceived sleep found a significant difference between light users (29.0%) and heavy users (53.5%) (p=0.02) regarding perceptions of insufficient sleep. According to this author1, "attention should be given to media use before sleep as a cause of perceived insufficient sleep".

An earlier study by the present authors2 found that adolescents who used the computer during the night perceived poorer sleep quality (74.04%) to a significantly greater extent than non-users did. Nevertheless, we did not expect internet use between 19:00 and 24:00 to be the greatest risk factor for poor sleep among university students.

Studies that might explain our findings have explored the effect of light exposure on circadian rhythms and have demonstrated that exposure to light before 24:00 leads to delays in the circadian phase, whereas exposure after 24:00 induces phase advances, thereby changing sleep cycles. Studies involving strong light showed a more significant impact on the circadian clock than did those with weak light. These studies concluded that the sensitivity of circadian rhythms to the effects of light exposure on the retina varies according to the circadian phase within which light exposure takes place11-13,24-27.

Based on our findings, we posit that proximity to the computer screen between 19:00 and 24:00 induced a significant light effect that changed the participants' sleep cycles and contributed towards poorer quality sleep. Another factor may be related to the interactivity patterns of computer use, in which computer users tend not to interrupt their use. In contrast, TV viewing is less contiguous or intense, such that users more readily discontinue the activity temporarily. Exploring these hypotheses was beyond the scope of the present study and could be the topic of future investigations.

Takahashi and Arito29 showed that performing mental tasks before sleep can curtail the duration of slow wave sleep within the first cycle.

However, a study by Higuchi et al.4 on the display light of electronic games between 23:00 and 01:45 among a group of young adults, found no effect on the physiological variables of sleep. According to these authors, the combination of the compelling nature of the game and the display brightness may change the perception of sleep quality.

Our results indicate that the fact that these young adults watched television (Table 3) was not linked to any significant risk of a perception of poor quality sleep, although an earlier study had shown that watching TV for three or more hours consecutively contributed towards a significantly higher risk of frequent sleep problems5.

Correlation analysis (Table 4) between non-use of the computer at any time and use during the nighttime periods studied showed that computer use between 19:00 and 22:00 or between 19:00 and 24:00 was associated with higher frequency of poor sleepers.

Despite the large sample size used in this study and the valuable data pooled, causal relationships could not be fully examined here because this was a field study among students from only one university.

In conclusion, the data on computer use between 19:00 and 21:00 or between 19:00 to 24:00 that we collected allowed us to conclude that computer use increases the risk of poor sleep among university students. However, perceptions of sleep relating to TV viewing during the same periods did not present the same risk.



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Gema Mesquita
Rua Euclides da Cunha 202
37130-000 Alfenas MG, Brazil

Received 18 October 2009
Received in final form 9 March 2010
Accepted 16 March 2010



State University of Campinas (UNICAMP), Campinas SP, Brazil and the University of São Paulo Medical School (FMUSP), São Paulo SP, Brazil.

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