title: Habitual sleep-wake behaviors and lifestyle as predictors of diurnal cortisol patterns in young breast cancer survivors: a longitudinal study.
abstract: OBJECTIVE
  This study aimed to identify predictors of changes in diurnal cortisol patterns during the 8-month follow up period for young breast cancer survivors. Among the potential predictors were tumor size, lymph node metastasis, changes in sleep problems, habitual time of awakening and bedtime, physical activity levels, body mass index (BMI), and depressive levels across 8 months.
  
  
  METHODS
  The participants were 62 breast cancer women who were aged 40 years and below, and had completed active breast cancer treatment. The longitudinal data were collected at four points: baseline assessment (T0) and three follow-ups after baseline: T1 (in the 2nd month), T2 (in the 5th month), and T3 (in the 8th month). The participants collected their salivary cortisol at home at six time points: upon waking, 30 and 45min after waking, and at 1200h, 1700h, and 2100h. They also completed several questionnaires: the Medical Outcomes Study Sleep scale; the Beck Depression Inventory-II, physical activity levels on a 10-point scale, time of going to bed, time of awakening, and total sleep hours.
  
  
  RESULTS
  This study found that the main predictors of changes toward flatter diurnal cortisol patterns during the 8-month follow ups were greater tumor sizes, increases of BMI scores, and habitually later times of awakening.
  
  
  CONCLUSIONS
  While greater tumor sizes represent biological vulnerability of disruption of cortisol circadian rhythm, maintaining an appropriate BMI and good sleep habits could be a protective factor for normal cortisol regulation, which likely helps to reduce early mortality in young breast cancer survivors.
authors.affiliation: School of Nursing, College of Medicine, National Taiwan University, No.1, Jen-Ai Rd. Sec. 1, Taipei, Taiwan. Electronic address: hsiaofei@ntu.edu.tw.
authors.forename: Fei-Hsiu
authors.initials: FH
authors.lastname: Hsiao
authors.affiliation: Department of Surgery, College of Medicine, National Taiwan University, Taiwan; Breast Center, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: brcancer@gmail.com.
authors.forename: Wen-Hung
authors.initials: WH
authors.lastname: Kuo
authors.affiliation: School of Medicine, Fu-Jen Catholic University, 510 Chung-Cheng Road, Hsin-Chuang, Taipei, Taiwan. Electronic address: 039666@mail.fju.edu.tw.
authors.forename: Guey-Mei
authors.initials: GM
authors.lastname: Jow
authors.affiliation: Department of Surgery, College of Medicine, National Taiwan University, Taiwan; Cheng Ching General Hospital, Taichung, Taiwan. Electronic address: Kingjen@ntu.edu.tw.
authors.forename: King-Jen
authors.initials: KJ
authors.lastname: Chang
authors.affiliation: Department of Surgery, Mackay Memorial Hospital, Taipei 10401, Taiwan. Electronic address: psyangd0039@gmail.com.
authors.forename: Po-Sheng
authors.initials: PS
authors.lastname: Yang
authors.affiliation: Department of Surgery, Mackay Memorial Hospital, Taipei 10401, Taiwan. Electronic address: hungbun@ms1.mmh.org.tw.
authors.forename: Hung-Bun
authors.initials: HB
authors.lastname: Lam
authors.affiliation: Department of Surgery, Mackay Memorial Hospital, Taipei 10401, Taiwan. Electronic address: jjlee@ms2.mmh.org.tw.
authors.forename: Jie-Jen
authors.initials: JJ
authors.lastname: Lee
authors.affiliation: Department of Surgery, College of Medicine, National Taiwan University, Taiwan; Breast Center, National Taiwan University Hospital, Taipei, Taiwan. Electronic address: huangcs@ntu.edu.tw.
authors.forename: Chiun-Sheng
authors.initials: CS
authors.lastname: Huang
authors.affiliation: Breast Cancer Caring Unit, Mackay Memorial Hospital, Taipei, Taiwan. Electronic address: sophia_7799@yahoo.com.tw.
authors.forename: Yu-Fen
authors.initials: YF
authors.lastname: Liu
authors.affiliation: School of Nursing, Chang-Gung University, 259 Wen-Hwa 1st Road, Kwei-Shan, Tao-Yuan, Taiwan. Electronic address: yulai@mail.cgu.edu.tw.
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Lai
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000628:therapy; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000378:metabolism*; D008019:Life Style; D008137:Longitudinal Studies; D009043:Motor Activity; D009367:Neoplasm Staging; D012463:Saliva / Q000737:chemistry; D012890:Sleep; D007319:Sleep Initiation and Maintenance Disorders / Q000378:metabolism*; D017741:Survivors; D047368:Tumor Burden; D014851:Wakefulness
chemical_list: D006854:Hydrocortisone
keywords: BMI; Diurnal cortisol patterns; Lifestyle; Physical activity level; Sleep problems; Young breast cancer survivors