A circadian rhythm gene (PER3) VNTR variant as possible risk factor in cohort of Turkish females with primary dysmenorrhea

Primary dysmenorrhea (PDM), which is the most prevalent problem related to the menstrual cycle in women of reproductive age, is due to sleep disorders and negative moods. Circadian rhythms, which are the immediate 24-h processes, enable an organism to adapt the suitable physiological responses to the environmental light-dark changes. Disturbed circadian rhythms are closely associated with several diseases, including sleep disorders. It has been reported that variable number tandem repeat (VNTR) variant in the coding region of circadian rhythm gene PERIOD 3 (PER3) affects sleep. Therefore, in the present study, we investigated the association between PDM and PER3 VNTR variant in Turkish females. A sample of 122 females with PDM and 150 healthy females were included in the study. Genoytyping of PER3 VNTR variant was performed on DNA by polymerase chain reaction (PCR) analysis using specific primers. We evaluated the relation between PER3 VNTR variant and PDM by calculating the odds ratios (ORs) and 95% confidence intervals (CIs). In our analyses of genotype data collected from total 272 subjects, we found that the PER3 VNTR variant was associated with development of PDM [codominant model (5/5 vs. 4/4 + 4/5): OR = 0.664; 95% CI, 0.39-1.10; p = 0.05). The three genotypes of the VNTR variant (4/4, 4/5, and 5/5) and their allelic frequencies showed nonsignificant differences between patients and control group (p > 0.05). In summary, PER3 VNTR variant may be associated with PDM in a Turkish female. However, further studies in different ethnic populations are needed to address the full role of this variant in PDM.