title: Rotating shift work and menstrual characteristics in a cohort of Chinese nurses.
abstract: Shift work disrupts the circadian rhythm and may cause menstruation disorders. This study assessed the impact of shift work on menstrual cycle in a population of Chinese nurses.
  
  
  
  Questionnaires on menstrual characteristics and shift schedules were sent to female nurses of the First Affiliated Hospital of Sun Yat-sen University (FAHSYSU) and Guanghua Hospital of Stomatology (GHHS), affiliated to Sun Yat-sen University. Part I was a cross-sectional study and included 139 nurses in GHHS who had regular 8:00-17:30 working (non-shift group), and 334 nurses from FAHSYSU who worked shifts, a response rate of 67.5 % and 59.6 %, respectively (age ≤ 50 years). Menstrual patterns were compared and age-adjusted relative risks of shift work were analyzed. Part II was a nested case-control study. Cases were nurses in Part I who had regular cycle with mean cycle length (MCL) of 25-31 days and but at least 3 days variation in MCL after starting shift work (n = 45). Controls consisted of 67 nurses with matching shift patterns and age, but no MCL changes. A control non-shift age-matched group consisted of 30 GHHS nurses with no MCL changes. A follow-up second questionnaire was sent 2 years later.
  
  
  
  In Part I, the shift group had a significantly higher proportion of nurses with menstrual cycle irregularity. The proportion of nurses with a cycle of 25-31 days decreased from 81.7 to 67.8 % after changing to shift work. Logistic regression analysis showed that night shift frequency was the only risk factor associated with cycle shortening. After adjusting for age, MCL was shorter when night work was performed > 7 times per month. In Part II, the mean change in MCL in the case group, including prolongation or shortening, was 4.115 ± 2.084 days after shift working. In the 2 years' follow-up, the MCL of the study group did not recover to the original length.
  
  
  
  Rotating shift work can increase the prevalence of menstrual cycle irregularity. Night shift frequency was the only risk factor associated with cycle reduced. Changes in MCL did not show recovery over a follow-up period of 2 years.
authors.affiliation: Reproductive Center, the 6th Building, the First Affiliated Hospital of Sun Yat-sen University, Zhongshan 2 Road No. 58, YueXiu District, Guangzhou, 510080, Guangdong Province, China.
authors.forename: Yizi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Reproductive Center, the 6th Building, the First Affiliated Hospital of Sun Yat-sen University, Zhongshan 2 Road No. 58, YueXiu District, Guangzhou, 510080, Guangdong Province, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Gu
authors.affiliation: Reproductive Center, the 6th Building, the First Affiliated Hospital of Sun Yat-sen University, Zhongshan 2 Road No. 58, YueXiu District, Guangzhou, 510080, Guangdong Province, China.
authors.forename: Mingfen
authors.initials: M
authors.lastname: Deng
authors.affiliation: Department of Biostatistics and Epidemiology, School of Public Health, Sun Yat-Sen University, Guangzhou, Guangdong Province, China.
authors.forename: Lan
authors.initials: L
authors.lastname: Guo
authors.affiliation: Department of Biostatistics and Epidemiology, School of Public Health, Sun Yat-Sen University, Guangzhou, Guangdong Province, China.
authors.forename: Ciyong
authors.initials: C
authors.lastname: Lu
authors.affiliation: Reproductive Center, the 6th Building, the First Affiliated Hospital of Sun Yat-sen University, Zhongshan 2 Road No. 58, YueXiu District, Guangzhou, 510080, Guangdong Province, China.
authors.forename: Canquan
authors.initials: C
authors.lastname: Zhou
authors.affiliation: Nursing Department, the First Affiliated Hospital of Sun Yat-sen University, Zhongshan 2 Road No.58, YueXiu District, Guangzhou, Guangdong Province, 510080, China. chenshouzhen001@126.com.
authors.forename: Shouzhen
authors.initials: S
authors.lastname: Chen
authors.affiliation: Reproductive Center, the 6th Building, the First Affiliated Hospital of Sun Yat-sen University, Zhongshan 2 Road No. 58, YueXiu District, Guangzhou, 510080, Guangdong Province, China. xuyanwen@live.cn.
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000328:Adult; D015992:Body Mass Index; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D002681:China; D002940:Circadian Rhythm / Q000502:physiology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008598:Menstruation / Q000502:physiology* / Q000523:psychology; D008875:Middle Aged; D009726:Nurses / Q000523:psychology* / Q000706:statistics & numerical data; D015995:Prevalence; D011795:Surveys and Questionnaires; D013997:Time Factors; D014940:Work Schedule Tolerance / Q000502:physiology* / Q000523:psychology
keywords: Circadian rhythm; Menstrual cycle; Nurses; Shift work