Sleep quality and its association with psychological distress and sleep hygiene: a crosssectional study among pre-clinical medical students

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1 274 Sleep qulity nd relted ftors ORIGINAL ARTICLE Sleep qulity nd its ssoition with psyhologil distress nd sleep hygiene: rosssetionl study mong pre-linil medil students Mojt Rezei 1 Moein Khormli 1,2 Smneh Akrpour 3 Khosro Sdeghniit-Hgighi 1 Mnsour Shmsipour 4,5 1 Ouptionl Sleep Reserh Center, Bhrloo Hospitl, Tehrn University of Medil Sienes - Tehrn - Tehrn - Irn. 2 Students Sientifi Reserh Center, Tehrn University of Medil Sienes - Tehrn - Tehrn - Irn. 3 Deprtment of Epidemiology & Biosttistis, Shool of Puli Helth, Tehrn University of Medil Sienes - Tehrn - Tehrn - Irn. 4 Institute for Environmentl Reserh, Deprtment of Reserh Methodology nd Dt Anlysis,Tehrn University of Medil Sienes - Tehrn - Tehrn - Irn. 5 Institute for Environmentl Reserh (IER), Center for Air Pollution Reserh (CAPR), Tehrn University of Medil Sienes - Tehrn - Tehrn - Irn. ABSTRACT Ojetive: This study imed to investigte sujetive sleep qulity nd its ssoition with demogrphis, psyhologil helth, nd sleep hygiene relted ehviors in pre-linil medil students. Methods: In this ross-setionl study, self-dministered questionnire onsisting of demogrphis, sleep hygiene ehviors, Pittsurgh Sleep Qulity Index (PSQI), nd Depression, Anxiety nd Stress Sle-21 (DASS21) ws hnded out to ll medil students of Tehrn University of Medil Sienes t pre-linil stge. Results: The questionnire ws filled out y 553 (89.7%) of 616 students pprohed. Aout 60% of our smple hd glol PSQI sore of more thn 5 (ut off of poor sleep qulity) with men glol PSQI sore of 6.32 (SD=2.72). The prevlene of moderte to extremely severe depression, nxiety nd stress sores were 26.1%, 29.61%, nd 14.5% respetively. Poor sleep qulity ws ssoited with lter yer in the shool, psyhologil distress nd severl lifestyle ehviors. Construting multivrite logisti model, depression, nxiety nd some sleep hygiene ehviors were signifintly ssoited with higher PSQI sore. Disussion: Our findings suggest tht poor sleep qulity is ommon prolem mong pre-linil medil students nd is ssoited with some psyhologil symptoms nd sleep hygiene ehviors. This issue demonstrtes neessity of interventions to improve the sleep qulity in this popultion group. Keywords: sleep; Students; Medil; ehvior. Corresponding uthor: Mnsour Shmsipour. E-mil: shmsmn87@yhoo.om Reeived: Mrh 17, 2018; Aepted: August 20, DOI: /

2 Rezei, et l. 275 INTRODUCTION Pre-linil medil students re in ritil period of quiring the neessry knowledge nd experiene tht would e useful for the rest of their edution nd reer. Therefore, this period neessittes omplete physil nd mentl helth. In ddition, high level of demi urden on students, exposes them to n inresed risk of different sleep prolems nd its relted onsequenes. In one study prevlene of dytime sleepiness is estimted to e s high s out 50% mongst students, whilst it is only 36% mongst the generl popultion 1. In nother study, it ws shown tht 40.6% of medil students suffer from poor sleep qulity 2. It n e hypothesized tht severl lifestyle ehviors, environmentl nd psyhologil ftors were ssoited with poor sleep qulity nd quntity. Sleep hygiene is set of ehviors tht is elieved to hve positive effet on oth sleep qulity nd quntity. Alohol use, ffeine nd energy drinks, stimulnts nd frequent use of tehnology suh s phone or omputers efore sleep re mong ommon ehviors tht re inomptile with sleep hygiene 3-9. Environmentl onditions like living in dormitories hve een ssoited with poor sleep qulity in previous studies 10,11. Psyhologil prolems suh s depression, nxiety, nd stress hve een ssoited with sleep disorders suh s insomni 12. Clinil stge of medil trining strts t the fourth yer in the usul urriulum of the Irnin medil shools nd it s ssoited with the night lls nd shifts. Whilst puli student ommunities nd some speil popultions hve een studied 3,13, to the est of our knowledge, no extensive study on the sleep ondition nd its ssoited ftors mong medil students t pre-linil stges hs een rried out. In this study, we imed to fous on this distint sugroup of students nd we imed to (1) ssess sleep qulity mongst different sugroups of medil students of Tehrn University of Medil Sienes t the prelinil stge, nd then to (2) identify speifi lifestyle ehviors, environmentl nd psyhologil ftors ssoited with poor sleep qulity mongst them. MATERIAL AND METHODS Prtiipnts nd proedures This is ross-setionl questionnire-sed study onduted from Deemer 2013 to Jnury 2014 nd ll medil students of Tehrn University of Medil Sienes t first, seond, nd third yers (616 students) were invited to prtiipte. Medil students t this level of edution re t pre-linil stge nd do not hve night lls or shifts. The questionnires were dministered on pper. Time for the distriution of the self-dministrted questionnires ws hosen refully pying ttention to the exms shedule of the students suh tht they hd no exm over period of 2 weeks efore nd fter filling out the questionnires. The study protool ws pproved y institutionl review ord nd ethi ommittee of Tehrn University of Medil Sienes. MEASURES Demogrphis nd sleep hygiene The survey inluded demogrphi questions ssessing ge, gender, nd yer t medil shool, mritl nd residentil sttus nd the numer of their roommtes. The ltter inludes the numer of people who shred the sme living environment in the dormitory (e.g., suite or room). We lso ssessed students sleep hygiene nd lifestyle ehviors y sking them 10 questions with responses inluding never, sometimes, often nd lmost lwys in regrd to tking fternoon nps lsting t lest one hour, going to ed t different times from dy to dy, getting out of ed t different times from dy to dy, using ed for tivities other thn sleeping, onsumption of ffeinted drinks suh s offee, tes nd energy drinks efore edtime, using eletroni devies efore edtime, going to ed lte in order to study for exms, diffiulty sleeping euse of different sleep shedules of roommte(s), hving n unomfortle room nd sleeping on n unomfortle ed. We ustomized questions sed on previous similr studies 4,14. Eh question ws nlyzed seprtely with no glol sore. Sleep qulity Pittsurgh Sleep Qulity Index (PSQI) ws used to ssess students sujetive sleep qulity. This is n interntionlly reognized tool for the evlution of sleep qulity during preeding month nd onsists of 19 items whih re omined to form seven susles: sujetive sleep qulity, sleep lteny, sleep durtion, hitul sleep effiieny, sleep disturnes, use of sleeping medition, nd dytime dysfuntion. Eh item ws sored on 3 point sle (rnging from 0 for non-diffiulty to 3 for severe diffiulty) nd the omintion of seven susles yields the glol PSQI sore whih rnges from 0 to 21. Sores greter thn 5 hve een shown to e inditive of poor sleep qulity. The PSQI hs high degree of internl onsisteny with n overll reliility oeffiient (Cronh s α) of 0.83 in the originl rtile. The glol utoff sore of 5 for distinguishing poor from good sleep qulity hs sensitivity of 86.9% nd speifiity of 86.5% 15. Although these figures were lulted sed on study with different smple properties (52 ontrols, 34 poor sleepers with mjor depression, 62 physiin-referred poor sleepers; with men ges of 59.9, 50.9 nd 44 respetively), the PSQI hs een previously used in severl studies to ssess medil students sleep qulity 3,16. Reliility nd vlidity of the Persin version of PSQI (PSQI-P) were verified in study onduted y Frrhi Moghddm et l. 17 The overll reliility oeffiient of the questionnire ws 0.73 in this study. Depression, nxiety, nd stress Depression, Anxiety, nd Stress Sle-21(DASS-21) ws used to ssess students mentl helth. Reommended utoff points for eh susle re s follows: Depression [norml (0-9), mild (10-13), moderte (14-20), severe (21-

3 276 Sleep qulity nd relted ftors 27), nd extremely severe (28+)], Anxiety [norml (0-7), mild (8-9), moderte (10-14), severe (15-19), nd extremely severe (20+)], Stress [norml (0-14), mild (15-18), moderte (19-25), severe (26-33), nd extremely severe (34+)] 18. Reliility nd vlidity of the Persin trnsltion of DASS- 21 were ssessed nd verified in study onduted y Asghri et l. 19. It hd n eptle internl onsisteny with n overll reliility oeffiient (Cronh s α) of 0.94 for totl sore nd 0.85, 0.85, nd 0.87 for depression, nxiety, nd stress susles respetively. The overll reliility oeffiient of the questionnire ws 0.90 in this study. Sttistis The student s independent t-test or nlysis of vrine test ws pplied to ssess the differenes in glol PSQI etween two or more thn two independent groups respetively. Chi-squre test ws used to ompre tegoril vriles in good vs. poor sleepers. Person s orreltion oeffiient ws pplied to ssess ssoition etween the numer of roommtes nd PSQI sore. Dt ws tested for normlity efore pplying prmetri nlysis. All vriles with p-vlue <0.1 in univrite nlysis plus gender were entered into multiple logisti regression model. As glol PSQI sore nnot e lulted if ny dt were missing, questionnires with missing PSQI vlues were eliminted from the dt nlysis. Other missing dt were of smll mount nd missing pttern were similr etween independent groups, so fter heking for rndom distriution, pirwise deletion method ws used. All nlyzes were done using the generl sttistil pkge Stt SE 12.0 (SttCorp LP, College Sttion Texs) nd p-vlues less thn 0.05 were onsidered signifint. RESULTS Demogrphis The questionnire ws filled out y 553 (89.7%) of the 616 students pprohed (63 questionnire were not returned or eliminted due to missing dt in PSQI), inluding 268 (48.5%) mles nd 281 (50.8%) femles. Of these, 177 (32%) were firstyer, 84 (15.2%) seond-yer, nd 292 (52.8%) third-yer medil students (our dt is omptile with the totl numer of students t eh yer) with men ge of (SD=1.11) rnging from 19 to 27 yers. The mjority of students delred tht they live with their fmilies or in university dormitories (262 [47.4%] or 230 [41.6%] respetively), nd the remining (58 [10.5%]) either live lone, or with friend or other forms. From those who live in dormitories, the numer of roommtes rnges from 1 to 9, with the men of 4.15 (SD=1.47) roommtes. Only 4 (0.7%) students in this survey were mrried, ll others were single. PSQI The men omponent sores nd men glol sores re shown in Tle 1. Among ll students, the men glol PSQI sore ws 6.32 (SD=2.72(. There were 332 (60.0%) prtiipnts Tle 1. PSQI glol nd susle mens. Sleep qulity Men SD Glol PSQI Susles Sujetive sleep qulity Sleep lteny Sleep durtion Hitul sleep effiieny Sleep disturnes Use of sleep meditions Dytime dysfuntion PSQI=Pittsurgh Sleep Qulity Index. with glol PSQI sore>5 whih re lssified s poor sleepers, nd 221 (40%) with sore of 5 whih re lssified s good sleepers. Sujetive sleep qulity, sleep durtion nd dytime dysfuntion hd mens ove 1, identifying these omponents s the min ontriutors to the glol PSQI sore 3,20. Anlysis of sleep timing shows tht 129 (23.32%) students go to ed efore midnight nd 424 (76.68%) fter midnight. Men sleep durtion ws 6.32 (SD=1.43), nd only 184 (33.3%) reported sleeping 7 hours or more s the minimum required sleep time in this genertion ording to Ntionl Sleep Foundtion s reommendtion 21, onsidering tht optiml sleep durtion my e even longer 22. The men glol sore of the different demogrphi sugroups is shown in Tle 2. Aording to the dt in this tle, erlier lss yers reported etter sleep qulity ompred with the lter lss yers (p-vlue=0.026). A post-ho Tukey test showed tht glol PSQI sore of first yer nd seond yer students differs signifintly (p-vlue=0.02), while other pirs doesn t hve ny signifint differene. There ws no signifint differene in sleep qulity sed on gender nd resideny sttus. There ws lso no signifint ssoition etween numer of roommtes nd glol PSQI sore (r=-0.02, p-vlue=0.85). Assoition etween sleep qulity nd mritl sttus ouldn t e investigted euse of the smll frequeny of mrried students. DASS-21 Men DASS-21 sore for depression, nxiety, nd stress were 9.70 (SD=6.99), 6.93 (SD=5.96), 6.01 (SD=3.42) respetively. Frequeny nd perentge of students with psyhologil distress re shown in Tle 3. An overll prevlene of moderte to very severe depression, nxiety nd stress ws founded to e 26.1%, 29.61% nd 14.5%, respetively. The students with etter psyhologil sttus hd signifintly lower glol PSQI sores (p-vlue). A post ho Tukey test showed tht ll pirs of psyhologil levels hve signifint differene in glol PSQI sore (p-vlue<0.05) exept mild vs. moderte nd moderte vs. severe levels in depression, nxiety nd stress tegory; in ddition to severe vs. extremely severe levels in depression nd nxiety tegory; nd norml vs. mild levels in nxiety tegory.

4 Rezei, et l. 277 Tle 2. Assoition etween demogrphis nd sleep qulity (men PSQI sore). Chrteristis Numer (%) Men (SD) PSQI Sore p-vlue Yer in the urriulum (2.47) 2 84 (15.2%) 6.93 (3.35) (52.8%) 6.36 (2.63) Missing dt 0 (0%) Gender Mle 268 (48.5%) 6.21 (2.63) Femle 281 (50.8%) 6.44 (2.80) Missing dt 4 (0.7%) Resideny With fmily 262 (47.4%) 6.18 (2.76) Dormitory 230 (41.6%) 6.58 (3.07) Other 58 (10.5%) 7.17 (2.63) Missing dt 2 (0.5%) Mritl sttus Single 548 (99.1%) 6.30 (2.70) Mrried 4 (0.7%) 8.50 (4.66) Missing dt 1 (0.2%) Numer of roommtes (29.1%) 6.31 (2.45) (61.3%) 6.54 (2.62) (9.6%) 6.32 (2.83) Missing dt 0 (0%) PSQI=Pittsurgh Sleep Qulity Index SD=Stndrd Devition Post- ho test showed tht the differene is etween the first yer group nd the seond yer group (p-vlue=0.02) Inluding lone, with friend or other undetermined forms. Beuse of low numer of mrried students, p-vlue ws not lulted. Sleep hygiene Frequeny nd perentge of responses never or sometimes nd often or lmost lwys to eh question re s shown in Tle 4. We grouped the responses to summrize the dt, however sttistil nlysis without grouping the responses showed similr results. Aording to these results, poor sleepers tend to tke dytime nps lsting one hour or more, go to nd out of ed t different times from dy to dy, drink ffeine-ontining drinks within 4 hours efore edtime, use eletroni devies efore edtime, go to ed lte euse they hve to study, hve distured sleep due to the different sleepwke shedules of their roommtes, nd/or sleep in n unomfortle room. Assoited ftor with poor sleep qulity To evlute ftors ssoited with poor sleep qulity, we onstruted multivrite logisti model from ll vriles with p-vlue < 0.1 in univrite nlysis plus gender. Glol PSQI sore > 5 ws onsidered s the dependent vrile in the logisti regression model. As presented in Tle 5, depression, nxiety nd some sleep hygiene ehviors were found to e signifintly ssoited with poor sleep qulity. Tle 3. Assoition etween psyhologil disorders nd sleep qulity (men glol PSQI sore). Psyhologil disorder Numer (%) Men Glol PSQI sore p-vlue (SD) Depression Norml 295 (53.3%) 5.52 (2.30) Mild 98 (17. 7%) 6.53 (2.21) Moderte 101 (18.3%) 7.40 (2.62) Severe to extremely se-vere 38 (6.9%) 9.32 (3.87) Missing dt 21 (3.8%) Anxiety Norml 319 (57.7%) 5.67 (2.37) Mild 62 (11.2%) 6.39 (2.39) Moderte 101 (18.3%) 6.98 (2.70) Severe to extremely se-vere 59 (10.7%) 8.61 (3.18) Missing dt 12 (2.2%) Stress Norml 381 (68.9%) 5.22 (2.84) Mild 72 (13%) 5.82 (2.35) Moderte 53 (9.6%) 7.10 (2.48) Severe to extremely se-vere 24 (4.3%) 7.85 (2.47) Missing dt 23 (4.2%) PSQI=Pittsurgh Sleep Qulity Index SD=Stndrd Devition Post- ho test showed tht the differene is signifint in ll levels (p-vlue<0.05) exept mild vs. moderte, moderte vs. severe nd severe vs. extremely severe levels. Post- ho test showed tht the differene is signifint in ll levels (p-vlue<0.05) exept norml vs. mild, mild vs. moderte, moderte vs. severe nd severe vs. extremely severe levels. Post- ho test showed tht the differene is signifint in ll levels (p-vlue<0.05) exept mild vs. moderte nd moderte vs. severe levels. DISCUSSION Pre-linil students go through n intensive ourse efore entry into the linil wrds nd ontt with ptients. It is thus useful to monitor the well-eing of these students efore they proeed to the next stge. There re limited reserhes investigting sleep hits of this sugroup whih n hve oth helth nd demi implitions. Our study imed to evlute sleep qulity nd its relted ftors mongst medil students t the pre-linil stge. Our results showed tht over hlf of prtiipnt in our study reveled poor sleep qulity nd out 60% of our smple hd glol PSQI sore of more thn 5 (utoff point for poor sleep qulity) with men glol PSQI sore of 6.32 (SD=2.72) 3,16,20. This n e explined y severl ftors tht were prtilly investigted in this study. We oserved no signifint differene in sleep qulity mong mle nd femle students, whih is onsistent with the findings of nother study onduted y Ctes et l. 20. However, some studies hve reported tht femle medil students hve poorer sleep qulity ompred with mle medil students 16,23. It seems likely tht ulturl differenes etween ountries my ply role in the differenes etween these results. The differenes in sleep qulity etween students of different yer groups oserved in this study is in ontrst with the

5 278 Sleep qulity nd relted ftors Tle 4. Assoition etween sleep hygiene nd sleep qulity. Question Never & Sometimes (%) Often & Almost Alwys (%) Missing dt p-vlue I tke dytime nps lsting one hour or more Poor sleepers 179 (53.9%) 151 (45.5 %) 2 (0.6%) Good sleepers 155 (70.1%) 66 (29.9%) 0 I go to ed t different times from dy to dy Poor sleepers 237 (71.4%) 91 (27.7%) 4 (1.2%) Good sleepers 191 (86.4%) 29 (13.2%) 1 (0.5%) I go out of ed t different times from dy to dy Poor sleepers 248 (74.7%) 63 (19%) 21 (6.3%) Good sleepers 199 (90%) 16 (7.2%) 6 (2.7%) I use ed for tivities other thn sleeping Poor sleepers 193 (58.1%) 138 (41.6%) 1 (0.3%) Good sleepers 142 (64.3%) 78 (35.3%) 1 (0.5%) I drink ffeine ontining drinks suh s te, offee or energy drinks within 4 hours efore edtime Poor sleepers 221 (66.6%) 110 (33.1%) 1 (0.3%) Good sleepers 180 (81.4%) 41 (18.6%) 0 I use eletroni devies suh s TV, omputer or ell phone efore edtime Poor sleepers 47 (14.2%) 283 (85.2%) 2 (0.6%) Good sleepers 58 (26.2%) 163 (73.8%) 0 I go to ed lte euse I hve to study my lessons Poor sleepers 216 (65.1%) 112 (33.7%) 4 (1.2%) Good sleepers 159 (71.9%) 59 (26.7%) 3 (1.4%) My roommtes prevented me from sleeping euse of their different sleep-wke shedule Poor sleepers 248 (74.7%) 43 (43%) 41 (12.3%) Good sleepers 185 (83.7%) 10 (4.5%) 26 (11.8%) I sleep on n unomfortle ed Poor sleepers 303 (91.3%) 26 (7.8%) 3 (0.9%) Good sleepers 209 (94.6%) 9 (4.1%) 3 (1.4%) I sleep in n unomfortle room Poor sleepers 302 (91%) 28 (8.4%) 2 (0.6%) Good sleepers 215 (97.7%) 5 (2.3%) 1 (0.5%) p-vlue is referred to tegories of sujets (poor sleepers vs. good sleepers) defined s PSQI glol sore > 5 defined s PSQI glol sore >5 defined s PSQI glol sore results of previous studies 3. Lter yers reported worse sleep qulity ompred with the former lss yers. One explntion for this phenomenon n e tht lter yer students fe reltively hevier edutionl urden nd this issue mye ffets the psyhologil distress mong them. Another hypothesis is tht s students get older, they tke more time with their friends insted of their fmilies in the university nd dormitories, so this ft n dversely ffet sleep hygiene. High prevlene of psyhologil distress nd its strong ssoition with poor sleep qulity mongst medil students were lso oserved in the present study. Similr results hve een reported y previous studies using DASS-21. A depression prevlene of 37.2%, n nxiety prevlene of 63%, nd stress prevlene of 23.7% mong Mlysin medil students hve een reported 24. Aording to study in Sudi Ari, the prevlene of moderte to extremely severe level of depression, nxiety, nd stress mong Sudi Arin medil students were 52.4%, 46%, nd 56% respetively 25. It seems tht high demi urden on medil students plys mjor role in the prevlene of psyhologil distress. Although sleep disturne n e either use or symptom of psyhologil distress or simply e omoridity, there is some evidene tht shows psyhologil distress n e used y insomni 26. In view of these, prompt ttempt should e mde to etter understnd the nture of reltion etween sleep sttus nd psyhologil distress. Studies re needed to find out the most importnt uses nd onsequenes of psyhologil distress. Sleep hygiene hs onsiderle role in the qulity of sleep mong medil students. Poor sleep hygiene hve een

6 Rezei, et l. 279 Tle 5. Multiple regression model of ftors ssoited with poor sleep qulity. Chrteristis Crude OR (95% CI) Adjusted OR (95% CI) p-vlue(for Adjusted OR) Yer in the urriulum ( ) 0.91 ( ) ( ) 0.98 ( ) 0.94 Gender Femle 0.78 ( ) 1.34 ( ) 0.12 Psyhologil disorder Depression 2.22 ( ) 1.86 ( ) Anxiety 2.63 ( ) 1.93 ( ) Stress 1.20 ( ) 1.48 ( ) 0.12 Sleep hygiene ehviors I go to ed t different times from dy to dy 2.10 ( ) 1.87 ( ) 0.03 I go out of ed t different times from dy to dy 2.03 ( ) 1.27 ( ) 0.35 I drink ffeine ontining drinks suh s te, offee or energy drinks within 4 hours efore edtime 1.76 ( ) 2.20 ( ) I use eletroni devies suh s TV, omputer or ell phone efore edtime 1.64 ( ) 1.87 ( ) 0.18 I go to ed lte euse I hve to study my lessons 1.27 ( ) 1.11 ( ) 0.73 My roommtes prevented me from sleeping euse of their different sleep-wke shedule 1.55 (1, ) 1.25 ( ) 0.27 I sleep on n unomfortle ed 1.44 ( ) 1.07 ( ) 0.80 I sleep on n unomfortle room 1.79 ( ) 1.14 ( ) 0.61 PSQI=Pittsurgh Sleep Qulity Index CI=Confidene Intervl Mle is onsidered s referene Norml is onsidered s referene Response never is onsidered s referene Glol PSQI sore > 5 is onsidered s the dependent vrile in the logisti regression model. previously reported to ssoite poor sleep qulity y severl studies 3,27. However, fter ontrolling for onfounders, esides depression nd nxiety, only irregulrity of the time to go to ed, nd ffeine use were the signifint explntory vriles. In other words, our results show tht some of the sleep hygiene ehviors re not so importnt when the psyhologil symptoms, irregulrity sleep shedule, nd ffeine intke were ontrolled nd there is onfounding etween sleep hygiene nd psyhologil symptoms. To the est of our knowledge, there is no extensive study investigting ssoition etween psyhologil symptoms nd sleep hygiene ehviors, nd their reltionship with sleep qulity. As next steps, studies with longitudinl designs (tht llow for ross-lgged nlysis) re proposed to etter understnd the most importnt nd effetive omponents of sleep hygiene ehviors nd their potentil onfounders. This is ross setionl study with high response rte of 89.7%, nd it s the first study tht fouses on pre-linil students sleep qulity in n Irnin popultion. The use of stndrdized mesure for sleep qulity nd psyhologil distress is nother dvntge of the present study. To the est of our knowledge, no previous study hs exmined the reltionship etween psyhologil distress nd sleep qulity using oth DASS-21 nd PSQI stndrd mesures. However, there re severl limittions in our study. First of ll, the ross-setionl methodology limits our ility to mesure sleep qulity hnges s the students go through the different levels of the prelinil stge, nd lso prevents us from finding uslity reltionship etween the different ftors. It is still unler tht ftors ssoited with poor sleep qulity re use or onsequene or simply omoridity, so determining the most pproprite intervention needs further investigtions. The use of ojetive mesure of sleep pttern suh s polysomnogrphy ould lso led to dditionl dt, however, it seems tht there is strong reltion etween sujetive nd ojetive mesurements 28. Further longitudinl nd interventionl studies re needed to overome these limittions. CONCLUSION To summrize, this study investigted the sleep qulity nd its relted ftors mongst pre-linil medil students of Tehrn University of Medil Sienes. We showed tht poor sleep qulity is ommon prolem in the popultion of students, nd it s ssoited with lter yer in the shool, psyhologil distress nd poor sleep hygiene. This study provides etter vision of ftors ssoited with poor sleep qulity nd points to the need for further evlution of sleep prolems. Funding: This study ws funded y Tehrn University of Medil Sienes (TUMS) projet grnt ( ).

7 280 Sleep qulity nd relted ftors Conflit of interest: The uthors delre tht they hve no onflit of interest. Compline with ethil stndrds: All proedures performed in studies involving humn Prtiipnts were in ordne with the ethil stndrds of the institutionl the study ws pproved y the institutionl ethni ommittee (IR.TUMS.REC ). Informed onsent: Informed onsent ws otined from ll individul prtiipnts inluded in the study verlly. REFERENCES 1. Oginsk H, Pokorski J. Ftigue nd mood orreltes of sleep length in three ge-soil groups: Shool hildren, students, nd employees. Chronoiol Int. 2006;23(6): Ghoreishi A, Aghjni AH. Sleep qulity in Znjn university medil students. Tehrn Univ Med J. 2008;66(1): Brik CA, Seely DL, Plermo TM. Assoition etween sleep hygiene nd sleep qulity in medil students. Behv Sleep Med. 2010;8(2): Tylor DJ, Brmoweth AD. Ptterns nd onsequenes of indequte sleep in ollege students: sustne use nd motor vehile idents. J Adoles Helth. 2010;46(6): Irish LA, Kline CE, Gunn HE, Buysse DJ, Hll MH. The role of sleep hygiene in promoting puli helth: A review of empiril evidene. Sleep Med Rev. 2015;22: Shimur A, Hideo S, Tkesu Y, Nomur R, Komd Y, Inoue T. Comprehensive ssessment of the impt of life hits on sleep disturne, hronotype, nd dytime sleepiness mong high-shool students. Sleep Med. 2018;44: Hysing M, Pllesen S, Stormrk KM, Jkosen R, Lundervold AJ, Sivertsen B. Sleep nd use of eletroni devies in dolesene: results from lrge popultion-sed study. BMJ Open. 2015;5(1):e Jin MJ, Yoon CH, Ko HJ, Kim HM, Kim AS, Moon HN, et l. The Reltionship of Cffeine Intke with Depression, Anxiety, Stress, nd Sleep in Koren Adolesents. Koren J Fm Med. 2016;37(2): Lemol S, Perkinson-Gloor N, Brnd S, Dewld-Kufmnn JF, Gro A. Adolesents eletroni medi use t night, sleep disturne, nd depressive symptoms in the smrtphone ge. J Youth Adoles. 2015;44(2): Mnsouri A, Mokhyeri Y, Mohmmdi Frrokhrn E, Tvkkol Z, Fotouhi A. Sleep Qulity of Students living in Dormitories in Tehrn University of Medil Sienes (TUMS) in Irn J Epidemiol. 2012;8(2): Dimitriou D, Le Cornu Knight F, Milton P. The Role of Environmentl Ftors on Sleep Ptterns nd Shool Performne in Adolesents. Front Psyhol. 2015;6: Buysse DJ, Angst J, Gmm A, Ajdi V, Eih D, Rössler W. Prevlene, ourse, nd omoridity of insomni nd depression in young dults. Sleep. 2008;31(4): Adulghni HM, Alrowis NA, Bin-Sd NS, Al-Suie NM, Hji AM, Alhqwi AI. Sleep disorder mong medil students: reltionship to their demi performne. Med Teh. 2012;34(Suppl 1):S Mstin DF, Bryson J, Corwyn R. Assessment of sleep hygiene using the Sleep Hygiene Index. J Behv Med. 2006;29(3): Buysse DJ, Reynolds CF 3rd, Monk TH, Bermn SR, Kupfer DJ. The Pittsurgh Sleep Qulity Index: new instrument for psyhitri prtie nd reserh. Psyhitry Res. 1989;28(2): Surni AA, Zhid S, Surni A, Ali S, Mueen M, Khn RH. Sleep qulity mong medil students of Krhi, Pkistn. J Pk Med Asso. 2015;65(4): Frrhi Moghddm J, Nkhee N, Sheini V, Grrusi B, Amirkfi A. Reliility nd vlidity of the Persin version of the Pittsurgh Sleep Qulity Index (PSQI-P). Sleep Breth. 2012;16(1): Antony MM, Bieling PJ, Cox BJ, Enns MW, Swinson RP. Psyhometri properties of the 42-item nd 21-item versions of the Depression Anxiety Stress Sles in linil groups nd ommunity smple. Psyhol Assess. 1998;10(2): Asghri A, Sed F, Dijni P. Psyhometri properties of the Depression Anxiety Stress Sles-21 (DASS-21) in non-linil Irnin smple. Int J Psyhol. 2008;2(2): Ctes ME, Clrk A, Woolley TW, Sunders A. Sleep Qulity Among Phrmy Students. Am J Phrm Edu. 2015;79(1): Hirshkowitz M, Whiton K, Alert SM, Alessi C, Bruni O, DonCrlos L, et l. Ntionl Sleep Foundtion s sleep time durtion reommendtions: methodology nd results summry. Sleep Helth. 2015;1(1): Kitmur S, Ktyose Y, Nkzki K, Motomur Y, O K, Ktsunum R, et l. Estimting individul optiml sleep durtion nd potentil sleep det. Si Rep. 2016;6: Suen LK, Hon KL, Tm WW. Assoition etween sleep ehvior nd sleep-relted ftors mong university students in Hong Kong. Chronoiol Int. 2008;25(5): Shmsuddin K, Fdzil F, Ismil WS, Shh SA, Omr K, Muhmmd NA, et l. Correltes of depression, nxiety nd stress mong Mlysin university students. Asin J Psyhitr. 2013;6(4): Aolshmt K, Hou XY, Strodl E. Psyhologil well-eing sttus mong medil nd dentl students in Mkkh, Sudi Ari: rosssetionl study. Med Teh. 2015;37(Suppl 1):S Ford DE, Kmerow DB. Epidemiologi study of sleep disturnes nd psyhitri disorders. An opportunity for prevention? JAMA. 1989;262(11): Jmes BO, Omoreg JO, Igerse OO. Prevlene nd orreltes of poor sleep qulity mong medil students t Nigerin university. Ann Nigerin Med. 2011;5(1): Loyz H MP, Ponte TS, Crvlho CG, Pedrotti MR, Nunes PV, Souz CM, et l. Assoition etween mentl helth sreening y self-report questionnire nd insomni in medil students. Arq Neuropsiquitr. 2001;59(2-A):180-5.