title: Declining melatonin levels and older people. How old is old?
abstract: OBJECTIVE
  The purpose of this study was to investigate whether melatonin levels in older cohorts within the 'aged' population were significantly lower than in younger 'aged' individuals and hence point to a possible confound in cross-sectional studies which group individuals over 55 in one category.
  
  
  METHODS
  Melatonin levels of 35 North Queensland residents over 55 years of age living in an aged-care facility, a retirement village or the general community were compared across three age groups.
  
  
  METHODS
  Subjects were ten 56-65 year olds, eighteen 66-75 year olds and seven over-75 year olds. Information was obtained on sleep, awakening, medical conditions and medications, with subsequent exclusion of those with known medical conditions and/or medications. Melatonin was collected by salivary samples at 2200 hours and concentrations were determined by immunoassay.
  
  
  RESULTS
  Mean melatonin levels were significantly lower (p=.03) in the 'oldest' (over 75 yrs) group compared to the 'youngest' (56-65 yrs) group.
  
  
  RESULTS
  The results of this preliminary study indicate that within the older population, melatonin levels appear to decline significantly with age.
  
  
  CONCLUSIONS
  Future studies of melatonin and ageing may benefit from a longitudinal approach, with older subjects sampled across time.
authors.affiliation: School of Psychology, James Cook University, Cairns, Queensland, Australia. Deborah.Graham@jcu.edu.au
authors.forename: Deborah
authors.initials: D
authors.lastname: Graham
authors.forename: Angus
authors.initials: A
authors.lastname: McLachlan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D000704:Analysis of Variance; D015331:Cohort Studies; D006801:Humans; D008550:Melatonin / Q000378:metabolism*; D008875:Middle Aged; D011863:Radioimmunoassay; D012463:Saliva / Q000378:metabolism
chemical_list: D008550:Melatonin