title: Effect of free-living daily physical activity on salivary secretory IgA in elderly.
abstract: OBJECTIVE
  The aim of this work was to assess the relationship in elderly subjects between free-living daily physical activity and mucosal immunity, especially salivary secretory immunoglobulin A (SIgA).
  
  
  METHODS
  Elderly volunteers (114 men and 170 women) aged 71.3 +/- 0.3 yr (range: 65-86 yr) participated in this study. Resting saliva samples were collected in the morning. Saliva samples stimulated by chewing a sterile cotton ball at a frequency of 60/60 s were collected. The SIgA concentration was measured using enzyme-linked immunosorbent assay (ELISA), and the SIgA secretion rate was calculated. Free-living step count (steps per day), energy expenditure (kJ x kg(-1) x d(-1)), and activity durations (min x d(-1)) at specific intensity levels (inactive, light, moderate, and vigorous) were evaluated using an electric pedometer. The data obtained were stratified by pedometer-determined steps per day using quartiles (Q1-Q4) for distribution.
  
  
  RESULTS
  Elderly in quartiles showed step counts of 2962 +/- 94, 5118 +/- 62, 6832 +/- 59, and 9951 +/- 264 steps per day. Significant differences were found in the mean step count (P<0.0001), energy expenditure (P<0.0001), and activity duration (P<0.0001) with increasing pedometer-determined activity quartiles. Both SIgA concentration and SIgA-secretion rate were significantly higher for Q3 than for Q1 (P<0.05). Meanwhile, saliva flow rates showed no significant differences across quartiles.
  
  
  CONCLUSIONS
  These results suggest that a free-living daily physical activity level of approximately 7000 steps per day might be regarded as a moderate daily physical activity target for elderly people to improve mucosal immune function.
authors.affiliation: Graduate School of Comprehensive Human Sciences, Doctoral Program of Sports Medicine, Tsukuba University, Ibaraki, Japan.
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Shimizu
authors.forename: Fuminori
authors.initials: F
authors.lastname: Kimura
authors.forename: Takayuki
authors.initials: T
authors.lastname: Akimoto
authors.forename: Takao
authors.initials: T
authors.lastname: Akama
authors.forename: Shinya
authors.initials: S
authors.lastname: Kuno
authors.forename: Ichiro
authors.initials: I
authors.lastname: Kono
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D007071:Immunoglobulin A, Secretory / Q000032:analysis* / Q000276:immunology; D007564:Japan; D008297:Male; D012463:Saliva / Q000276:immunology / Q000378:metabolism*; D016138:Walking / Q000502:physiology*
chemical_list: D007071:Immunoglobulin A, Secretory