title: Childhood Passive Smoking Exposure and Age at Menarche in Chinese Women Who Had Never Smoked: The Guangzhou Biobank Cohort Study.
abstract: OBJECTIVE
  We examined the associations between childhood passive smoking exposure and age at menarche in women who had never smoked in southern China.
  
  
  METHODS
  Among 30,518 participants in Guangzhou Biobank Cohort Study (GBCS) from 2003-2008, 20,061 women who had never smoked and had complete outcome data were included. Childhood passive smoking exposure was defined as living with 1 or more smokers in the same household during childhood. Data on the number of smokers in the household and frequency of exposure (density and frequency) were also obtained. Age at menarche was measured as a continuous variable.
  
  
  RESULTS
  11,379 (56.7%) participants were exposed to passive smoking during childhood. Compared to those with no passive smoking exposure during childhood, those with exposure ≥ 5 days/week had menarche 0.19 year (95% confidence interval (CI): 0.13-0.25) earlier on average. Those exposed to more than two smokers had menarche 0.38 year earlier (95% CI: 0.29-0.47). Childhood exposure was associated with early age at menarche (≤ 13 vs. >13 years), with an adjusted odds ratio of 1.34 (95% CI: 1.21-1.48) for high density, and 1.17 (95% CI: 1.09-1.26) for high frequency of exposure.
  
  
  CONCLUSIONS
  Childhood passive smoking exposure was associated with earlier age at menarche, with a dose-response relationship in Chinese women who had never smoked. If causal, the results support the promotion of smoking cessation in families with children, particularly young girls.
authors.affiliation: Institute of Geriatrics, Chinese PLA General Hospital, Beijing, China; Jinan Military Area CDC, Jinan, Shandong, 250014, China.
authors.forename: Shanshan
authors.initials: S
authors.lastname: Yang
authors.affiliation: Guangzhou Number 12 People's Hospital, Guangzhou, China.
authors.forename: Yali
authors.initials: Y
authors.lastname: Jin
authors.affiliation: Institute of Geriatrics, Chinese PLA General Hospital, Beijing, China; Beijing Key Laboratory of Aging and Geriatrics, Chinese PLA General Hospital, Beijing, China; State Key Laboratory of Kidney Disease, Chinese PLA General Hospital, Beijing, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: He
authors.affiliation: Guangzhou Number 12 People's Hospital, Guangzhou, China.
authors.forename: Chaoqiang
authors.initials: C
authors.lastname: Jiang
authors.affiliation: Public Health, Epidemiology and Biostatistics, University of Birmingham, Birmingham, United Kingdom.
authors.forename: Kar Keung
authors.initials: KK
authors.lastname: Cheng
authors.affiliation: Guangzhou Number 12 People's Hospital, Guangzhou, China.
authors.forename: Weisen
authors.initials: W
authors.lastname: Zhang
authors.affiliation: School of Public Health, the University of Hong Kong, Hong Kong, China.
authors.forename: Tai Hing
authors.initials: TH
authors.lastname: Lam
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000368:Aged; D018070:Biological Specimen Banks; D002648:Child; D002681:China; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008572:Menarche / Q000187:drug effects* / Q000502:physiology; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D012906:Smoke / Q000009:adverse effects*; D014026:Nicotiana / Q000009:adverse effects*; D014028:Tobacco Smoke Pollution / Q000009:adverse effects*
chemical_list: D012906:Smoke; D014028:Tobacco Smoke Pollution