Shift workers who experience sleep disturbances and exposure to light at night could be at increased risk for alterations in physiologic functions that are circadian in nature.
Methods
We investigated rotating shift work and menstrual cycle patterns in the Nurses' Health Study II using cross-sectional data collected in 1993 from 71,077 nurses aged 28-45 years who were having menstrual periods and were not using oral contraceptives. Log-binomial regression was used to estimate relative risks (RRs) and 95% confidence intervals (CIs).
Results
Eight percent of participants reported working rotating night shifts for 1-9 months, 4% for 10-19 months, and 7% for 20+ months during the previous 2 years. Irregular cycles (>7 days variability) were reported by 10% of participants. Seventy percent of women reported menstrual cycles of 26-31 days, 1% less than 21 days, 16% 21-25 days, 11% 32-39 days, and 1% 40+ days. Women with 20+ months of rotating shift work were more likely to have irregular cycles (adjusted RR = 1.23 [CI = 1.14-1.33]); they were also more likely to have cycle length <21 days (1.27 [0.99-1.62]) or 40+ days (1.49 [1.19-1.87]) (both compared with 26-31 days). For irregular patterns and for 40+ day cycles, there was evidence of a dose response with increasing months of rotating shift work. Moderately short (21-25 days) or long (32-39 days) cycle lengths were not associated with rotating shift work.
Conclusions
Shift work was modestly associated with menstrual function, with possible implications for fertility and other cycle-related aspects of women's health.
12 h rotating shifts are common in high-tech industries in Taiwan. The aim of this longitudinal study was to evaluate the effect of the disruption of circadian rhythms by the shift schedule on menstrual cycle length (MCL) and regularity of female workers at an optoelectronic company in Taiwan. We recruited females who worked rotating shifts in a clean room environment as the shift-work group and female office workers who worked normal business hours as the comparison group. Every participant recorded their MCL for each menstruation cycle up to eight consecutive months prospectively and provided demographic characteristics, reproductive history, and menstrual characteristics. We collected data on 1,135 and 117 menstruation cycles in the shift-work (n = 280) and comparison groups (n = 49). Whereas the two groups had similar group means for MCL and number of menstrual bleeding days, the prevalence of menstrual cycle irregularity (cycles <25 or >35 days) was higher in the shift-work group ( p = 0.04). Univariate and multivariate logistic regression analyses demonstrated that rotating shift work was an independent predictor of menstrual cycle irregularity (odds ratio = 1.71, 95% confidence interval: 1.03-2.88) after adjusting for shift-work history, employment duration, coffee consumption,and pre-employment menstrual cycle irregularity. Although further study is required to confirm our findings plus to explore prevention and control measures, our data indicate rotating shift work can increase the risk of MCL irregularity.
Sleep and Circadian Health · Shift Work and Light Exposure
Dysfunction in menstrual physiology has pronounced effects on quality of life, involving mood changes, body image, infertility, and pregnancy complications. Light exposure may affect menstrual cycles and symptoms through the influence of melatonin secretion. The purpose of this systematic review is to determine the current state of knowledge about the effects of light and melatonin secretion on menstrual phase and cycle alterations. A brief overview of the influence of melatonin on human physiology is included. There is evidence of a relationship between light exposure and melatonin secretion and irregular menstrual cycles, menstrual cycle symptoms, and disordered ovarian function. In women with a psychopathology such as bipolar disorder or an endocrinopathy such as polycystic ovary syndrome, there seems to be greater vulnerability to the influence of light-dark exposure. Research on the complex role of light-dark exposure in menstrual physiology has implications for treatment of menstrual-associated disorders.
Del Río JP et al., 2024·Front Psychol·
Open Access
Hormones produced by the hypothalamic-pituitary-adrenal-gonadal (HPAG) axis are crucial for modulating central nervous system (CNS) function and development throughout a person's life. Disruptions in HPAG function can impact psychological development, particularly during adolescence-a period marked by psychological growth and the maturation of the HPAG axis. An early indicator of HPAG alterations is ovulatory dysfunction (OD), a common condition among adolescents. This study explored the associations between neuroactive hormones and personal growth in adolescents with OD. Female participants aged 12-25 years with OD were recruited, and assessments were conducted to profile their basic hormonal levels and various dimensions of individual development, including self-concept clarity, sense of coherence, self-esteem, perfectionism, self-control, and mood states. Adolescents with OD (n = 117) had lower self-concept clarity and self-esteem compared to reference data. A significant portion of the sample displayed elevated levels of tension (71.25%), confusion (62.5%), fatigue (58.22%), and depression (52.6%). Self-esteem scores were negatively correlated with DHEAS (r = -0.224; p = 0.026) and glucose (r = -0.249; p = 0.010). Higher levels of free testosterone were associated with increased depression scores (coef = 0.2398; p = 0.002), whereas higher estradiol levels were linked to lower aggressiveness scores (coef = -0.0648; p = 0.001). These findings indicate that hormonal imbalances in adolescents with OD could affect personal growth. Further research is needed to establish causal relationships between the variables considered.
Polycystic ovary syndrome (PCOS) is a common reproductive disorder associated with an adverse cardiometabolic profile early in life. Increasing evidence links cardiovascular risk factors, such as diabetes and hypertension, to accelerated cognitive aging. However, less is known about PCOS and its relationship to brain health, particularly at midlife. Our goal was to investigate possible associations between PCOS and midlife cognitive function and brain MRI findings in an ongoing prospective study. We used data from the Coronary Artery Risk Development in Young Adults (CARDIA) study, a geographically diverse prospective cohort study of individuals who were 18-30 years at baseline (1985-1986) and followed for 30 years. We identified women with PCOS from an ancillary study (CARDIA Women's study (CWS); n = 1,163) as those with elevated androgen levels and/or hirsutism in conjunction with symptoms of oligomenorrhea. At year 30, participants completed cognitive testing, including the Montreal Cognitive Assessment, Rey Auditory Verbal Learning Test (RAVLT) (verbal learning and memory), Digit Symbol Substitution Test (processing speed and executive function), Stroop test (attention and cognitive control), and category and letter fluency tests (semantics and attention). A subset completed brain MRI to assess brain structure and white matter integrity. Multivariable linear regression models estimated the association between PCOS and outcomes, adjusting for age, race, education, and study center. Of the 1163 women in CWS, 907 completed cognitive testing, and of these, 66 (7.1%) met criteria for PCOS (age 54.7 years). Women with and without PCOS were similar for age, BMI, smoking/drinking status, and income. At year 30, participants with PCOS performed lower (mean z score; 95% CI) on Stroop (-0.323 (-0.69 to -7.37); p = 0.008), RAVLT (-0.254 (-0.473 to -0.034); p = 0.002), and category fluency (-0.267 (-0.480 to -0.040); p = 0.02) tests. Of the 291 participants with MRI, 25 (8.5%) met PCOS criteria and demonstrated lower total white matter fractional anisotropy, a measure of white matter integrity (coefficient (95% CI) -0.013 (-0.021 to -0.005); p = 0.002), though not abnormal white matter. Our results suggest that women with PCOS have lower cognitive performance and lower white matter integrity at midlife. Additional research is needed to confirm these findings and to determine potential mechanistic pathways including potential modifiable factors.