title: Association between melatonin secretion and nocturia in elderly individuals: a cross-sectional study of the HEIJO-KYO cohort.
abstract: OBJECTIVE
  Nocturnal voids are regulated by circadian biological rhythms, including decreased urine production and increased bladder storage capacity at night. A previous experimental study suggested that exogenous melatonin decreases urine production and increases bladder capacity in rats. However, little is known about whether melatonin secretion, which is considerably lower than exogenous melatonin, is associated with nocturia in humans. We evaluated the association between melatonin secretion and nocturia.
  
  
  METHODS
  In this cross-sectional study we examined 861 community based elderly individuals with a mean age of 72.1 years. We measured nocturnal void frequency and overnight urinary 6-sulfatoxymelatonin excretion as an index of melatonin secretion. Nocturia was defined as 2 or more nocturnal voids.
  
  
  RESULTS
  Univariate comparisons between the 261 and 600 study participants with and without nocturia, respectively, showed marginal to significant associations of nocturia with age, gender, body mass index, estimated glomerular filtration rate, calcium channel blockers, benign prostatic hyperplasia, total voided urine volume, urinary 6-sulfatoxymelatonin, duration in bed, day length, and daytime and nighttime physical activity. The multivariate logistic regression model adjusted for the former confounding factors revealed that higher urinary 6-sulfatoxymelatonin was significantly associated with a lower nocturia OR (adjusted OR 0.73, 95% CI 0.56-0.96, p=0.023). After adjustment for age, gender and duration in bed the mean volume of a single voided urine significantly increased with tertiles of increasing urinary 6-sulfatoxymelatonin (p for trend=0.022).
  
  
  CONCLUSIONS
  Melatonin secretion is significantly and inversely associated with nocturia in a general elderly population.
authors.affiliation: Department of Community Health and Epidemiology, Nara Medical University School of Medicine, Nara, Japan. Electronic address: obayashi@naramed-u.ac.jp.
authors.forename: Kenji
authors.initials: K
authors.lastname: Obayashi
authors.affiliation: Department of Community Health and Epidemiology, Nara Medical University School of Medicine, Nara, Japan.
authors.forename: Keigo
authors.initials: K
authors.lastname: Saeki
authors.affiliation: Department of Community Health and Epidemiology, Nara Medical University School of Medicine, Nara, Japan.
authors.forename: Norio
authors.initials: N
authors.lastname: Kurumatani
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000652:urine; D002940:Circadian Rhythm; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008550:Melatonin / Q000031:analogs & derivatives* / Q000652:urine; D008875:Middle Aged; D053158:Nocturia / Q000453:epidemiology* / Q000503:physiopathology / Q000652:urine; D001743:Urinary Bladder / Q000503:physiopathology*; D014554:Urination / Q000502:physiology*
chemical_list: D015415:Biomarkers; C054513:6-sulfatoxymelatonin; D008550:Melatonin
keywords: 6-sulfatoxymelatonin; aged; circadian rhythm; nocturia; urinary bladder