Salivary markers of stress in upper secondary school

U fiziološkom odgovoru na stres i kontroli stresnog odgovora uglavnom sudjeluju dvije komponente neuroendokrinog sustava, simpatičko-medularna (SAM) os, koja regulira prvi odgovor na stres i os hipotalamus-adenohipofiza-kora nadbubrežne žlijezde (HPAC), čija se aktivacija uočava 15 do 20 minuta nakon stresnog podražaja. Cilj ovog istraživanja bilo je ispitati bazalnu, fiziološku aktivnost SAM i HPAC osi te njihovu povezanost s nizom kovarijabli (spol, tip škole, turnus pohađanja nastave, ritam spavanja i budnosti te demografska, akademska i društvena obilježja) u zdravih učenika koji pohađaju završne razrede srednjih škola. Specifični ciljevi uključivali su ispitivanje koncentracije kortizola i aktivnosti alfa-amilaze kao salivarnih biljega odgovora na stres te istraživanje njihove povezanosti sa subjektivnim procjenama razine stresa i sa strategijama suočavanja sa stresom, kao i s polimorfizmima jednog nukleotida (SNP) gena za mineralokortikoidni i glukokortikoidni receptor (rs5522, rs6189, rs6190) te za vezni protein 5 za FK506 (rs1360780). U istraživanje su bila uključena 903 maturanta gimnazija i strukovnih škola iz četiri najveća grada u Hrvatskoj (Zagreb, Split, Rijeka i Osijek). Uzorci sline prikupljeni kod kuće, tijekom jednog radnog dana u tri vremenske točke (po buđenju, 30 do 45 minuta nakon buđenja i neposredno prije lijeganja), uzeti su za analizu koncentracija kortizola dok se aktivnost alfa-amilaze mjerila samo u jednom uzorku, neposredno po buđenju. Kako bi se ispitao cirkadijalni ritam lučenja kortizola analizirani su i indeksi lučenja kortizola (CAR, DCD, AUCG). Učenice su imale statistički značajno veće koncentracije kortizola u jutarnjim satima, dok se koncentracije kortizola neposredno prije lijeganja nisu razlikovale među spolovima. Učenice imaju različite obrasce priprema za izazove koji ih očekuju tijekom nadolazećeg dana u odnosu na učenike, imaju značajno viši CAR, izraženiji DCD, veći AUCG u odnosu na učenike koji su imali statistički značajno veću aktivnost alfa-amilaze. Turnus pohađanja nastave, koji svakako posljedično utječe na ritam spavanja i trajanje budnosti, pokazao se kao prediktor lučenja kortizola. Statistički značajne razlike većine varijabli kortizola potvrđene su između učenika koji pohađaju različite turnuse nastave (SCC30-45, CAR, DCD i AUCG). Učenici koji su se budili ranije i imali duže trajanje budnosti imali su veći CAR, niži DCD i veći AUCG. Nisu potvrđene statistički značajne razlike niti jedne ispitivane varijable u učenika koji pohađaju različite tipove škola (gimnazije vs. strukovne škole). Također, statistički značajne razlike između učenika i učenica bile su uočene i u subjektivnoj procjeni stresa, suočavanju te njihovoj povezanosti s koncentracijama i indeksima kortizola. Zabrinutost za budućnost su oba spola procijenila kao najstresniju domenu života, dok su učenice imale statistički značajno veću razinu ukupnog stresa u odnosu na učenike te su više koristile aktivno suočavanje sa stresom. U ovom su istraživanju pronađene statistički značajne razlike povezanosti alela G polimorfizma rs 5522 s višom koncentracijom kortizola po buđenju (P=0,036), nižim CAR-om (P=0,021), dok je povezanost s DCD-om bila granična (P=0,050). Može se pretpostaviti kako učenici s dokazanim alelom G imaju niži CAR te zbog toga pokazuju lošiju pripremljenost za stresne izazove u nadolazećem danu, unatoč nešto izraženijim vrijednostima DCD-a. Ovo istraživanje ukazuje na potrebu definiranja protokola prikupljanja uzoraka sline u nekliničkim uvjetima i metodoloških smjernica za populacijska istraživanja, ponajprije zbog postojanja niza kovarijabli koje utječu na mjerenje koncentracije kortizola i aktivnosti alfa-amilaze. Dobiveni rezultati doprinose saznanjima o spolnim razlikama u funkciji HPAC osi, koje bi se trebale primijeniti i tijekom provedbe preventivnih mjera u adolescenata te ranijeg otkrivanja skupina koje su posebno osjetljive na stresne poticaje.Physiological response to stress and the control of the stress response is mediated by two major components of the neuroendocrinological systems, sympathetic nervous (SAM) system and hypothalamic-pituitary-adrenal (HPA) axis. In the stress response, the SAM axis is first activated. About fifteen to twenty minutes following the SAM activation, the HPA axis is activated. The aim of the study was to examine basal, physiologically activity of the SAM and HPAC axis activity and to determine associations of various covariates (gender, school type, school shift, sleep-wake rhythm, demographic, academic and life style characteristics) with altered daily salivary cortisol profiles in healthy students attending finishing grades of secondary schools. Specific aims of the study were to analyse concentration of cortisol and activity of alpha- amylase, as salivary markers of stress reaction, to determine association of salivary markers of stress with stress perception and coping, and to determine associations of salivary markers of stress with single nucleotide polymorphisms (SNP) in the genes for the mineralocorticoid and glucocorticoid receptors (rs5522, rs6189, rs6190) and FK506 binding protein 5 (rs1360780). The study included 903 secondary school students enrolled in the finishing classes of gymnasiums and vocational schools from the four largest cities in Croatia (Zagreb, Split, Rijeka and Osijek). The saliva samples were collected at students’ homes, over the course of one weekday. Salivary cortisol was sampled at three time points: at awakening, 30 to 45 after wakening and at bedtime. Salivary alpha-amylase was sampled at awakening. In order to analyse the circadian rhythm of salivary cortisol secretion, three indexes were analysed (CAR, DCD and AUCG).Females had higher morning concentrations of salivary cortisol than males, whereas bedtime cortisol concentrations were not different in females and males. Females had different salivary cortisol profile and different mechanisms for preparing for the anticipated stress of the upcoming day, higher CAR, steeper DCD and larger AUCG than males. On the other side, males had higher activity of salivary alpha-amylase. School shift, and therefore the sleep-wake up rhythm, was an important predictor of the secretion of salivary cortisol. There were statistically significant differences in two school shifts with respect to the majority of salivary cortisol measures (SCC30-45, CAR, DCD and AUCG). Students who woke-up earlier and were longer awake had larger CAR, flatter DCD and larger AUCG. Students from two types of schools (gymnasiums vs. vocational schools) did not differ in any of the measured salivary variables. Furthermore, female and male students differed significantly in stress perception, coping and associations between stress perception, coping and salivary cortisol concentrations and indexes. Future was rated as the most stressful problem domain in both sexes. The perception of total stress was higher in females than males, and females used more active coping than males. Finally, we found statistically significant differences in associations between G allele of rs 5522 polymorphism and higher cortisol concentration at awakening (P=0.036), lower CAR (P=0.021) and higher DCD (P=0.050), but at borderline. It can be hypothesized that the G allele is associated with the lower CAR and therefore, decreased ability of preparing for the anticipated stress (despite borderline association with the steeper DCD). This study points to the need for defining the protocol for salivary sampling in non-clinical conditions and developing methodological guidelines for population-based research, primarily due to the number of co-variables that affect the concentration of salivary cortisol and the activity of salivary alpha-amylase. Obtained results contribute to better understanding of sex differences in the functioning of the HPA axis, which should be considered in the prevention of various psychopathological conditions in adolescence and used for earlier identification of vulnerable groups at high risk of stress-related health problems