Comparisons of the VNTR Polymorphism in the Human Per3 Gene, Diurnal Preferences and Sleep Among Working College Students

*Corresponding author e-mail; fmfische@usp.br Introduction: In humans Per3 VNTR polymorphism consists of 4 or 5 repeats of exonic sequence of 54bp. This work aimed to investigate the associations between sleep variables and 1) VNTR polymorphism in Per3 gene and 2) diurnal preferences score, during workdays and free days. Methods: Subjects were students engaged in full-time jobs from Monday to Friday and attending evening classes at a public College in São Paulo, Brazil. A hundred students (males n=55, females n=45), from 21 to 26 years old, filled out a questionnaire about sleeping times (during working days and free days) and the Horne-Östberg (HO) questionnaire for diurnal preferences. They also provided a salivary DNA sample. The length polymorphisms in the hPer3 gene were genotyped using polymerase chain reaction. The test and two way ANOVA were used to assess proportions and mean differences between VNTR polymorphism in Per3 gene and sleep variables (sleep onset, sleep offset and sleep duration), during work days (Monday to Friday) and free days (Friday to Sunday). The same procedure was performed with the diurnal preference score. Results: 40.0% students were homozygous 4-repeat (4/4), 51.0% heterozygous (4/5) and 9.0% homozygous 5-repeat allele (5/5). About diurnal preferences score, 19% were considered as evening type, 66% as intermediary type and 5% as morning type. There was no association between Per3 VNTR polymorphism and diurnal preference score (2=3.84, p=.428). During work days there was no significant difference between VNTR polymorphism in Per3 gene and sleep onset (p=.169; p=.717), sleep offset (p=.665; p=.514) and sleep duration (p=.087; p=.852). During free days the sleep onset was later in evening type with genotype 4/5 (03:15h) than morning type of the same genotype (01:15h) (F=2,163; p = 0,009). Regarding diurnal preferences score, during work days, there was no significant difference on sleep onset (p=.218), sleep offset (p=.l 17) and sleep duration (p=.767). During free days, the sleep onset among evening types was delayed in 79.9 minutes compared to morning types and 68.1 minutes compared to indifferent types (p=.008). The sleep offset among evening types was also delayed compared to morning types (107.0 minutes) and indifferent types (79.7 minutes) (p=<.001). There was no significant difference between diurnal preference score and sleep duration during free days (p=.729). Conclusion: During free days on weekends when there is no social constrains to sleep onset and offset times the different chronotypes express different sleep profiles that are associated in part with Per3 VNTR genotype. Support: CNPq, CAPES, AFIP, Sleep Institute, Federal University of São Paulo, Brazil. Publication History Article published online: 16 June 2026 © 2009. Brazilian Sleep Academy. This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/) Thieme Revinter Publicações Ltda. Rua Rego Freitas, 175, loja 1, República, São Paulo, SP, CEP 01220-010, Brazil