title: Diurnal cortisol patterns are associated  with physical performance in the Caerphilly  Prospective Study.
abstract: BACKGROUND
  Cross-sectional studies have suggested that elevated cortisol is associated with worse physical performance, a surrogate of ageing. We examined the relationship between repeat cortisol measures over 20 years and physical performance in later life.
  
  
  METHODS
  Middle-aged men (45-59 years) were recruited between 1979 and 1983 (Phase 1) from the Caerphilly Prospective Study (CaPS) and re-examined 20 years later at 65-83 years of age (Phase 5). Participants included 750 and 898 subjects with either Phase 1 and/or Phase 5 data on exposure and outcomes. Outcome measures were walking speed and balance time and exposures included morning fasting serum cortisol (Phase 1) and four salivary samples on 2 consecutive days (Phase 5).
  
  
  RESULTS
  Faster walking speed was associated with higher morning cortisol at Phase 1 [coefficient per standard deviation (SD) increase 0.68, 95% confidence interval (95% CI) 0.09-1.27; P=0.02] though this was attenuated after adjustment for covariates (coefficient per SD increase 0.45; 95% CI -0.16 to 1.07; P=0.15). Higher night-time cortisol at Phase 5 was associated with slower speed (coefficient per SD increase -1.06; 95% CI -1.60 to -0.52; P<0.001) and poorer balance (odds ratio of top tertile vs bottom 2.49; 95% CI 1.63-3.81; P<0.001). Worst performance was seen for men with a poor morning response (Phase 1) and less nocturnal decline (Phase 5).
  
  
  CONCLUSIONS
  Dysregulation of the hypothalamic pituitary adrenal (HPA) axis is associated with worse physical performance in later life. This may reflect a causal effect of the HPA axis on ageing or that ageing itself is associated with reduced HPA reactivity.
authors.affiliation: School of Social and Community Medicine, University of Bristol, Canynge Hall, Bristol, UK.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Gardner
authors.forename: Stafford L
authors.initials: SL
authors.lastname: Lightman
authors.forename: John
authors.initials: J
authors.lastname: Gallacher
authors.forename: Rebecca
authors.initials: R
authors.lastname: Hardy
authors.forename: Diana
authors.initials: D
authors.lastname: Kuh
authors.forename: Shah
authors.initials: S
authors.lastname: Ebrahim
authors.forename: Antony
authors.initials: A
authors.lastname: Bayer
authors.forename: Yoav
authors.initials: Y
authors.lastname: Ben-Shlomo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D015992:Body Mass Index; D002940:Circadian Rhythm / Q000502:physiology*; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D010913:Pituitary-Adrenal System / Q000378:metabolism; D004856:Postural Balance / Q000502:physiology*; D011446:Prospective Studies; D012463:Saliva / Q000737:chemistry*; D012907:Smoking; D016138:Walking / Q000502:physiology*
chemical_list: D006854:Hydrocortisone