title: Decreased salt intake in Japanese men aged 40 to 70 years and women aged 70 to 79 years: an 8-year longitudinal study.
abstract: BACKGROUND
  It is not known whether salt intake decreases over time in the same population. This study attempts to describe salt intake for 8 years according to age groups, and examines whether salt intake changes over time in community-dwelling middle-aged and elderly Japanese subjects.
  
  
  METHODS
  Data were collected as part of the National Institute for Longevity Sciences Longitudinal Study of Aging. Participants included 544 men and 512 women who participated in and completed all nutrition surveys from the first (1997-2000) to fifth (2006-2008) study waves. Each study wave was conducted for 2 years; in individuals, the entire follow-up period was 8 years. Salt and energy intake were calculated from 3-day diet records with photographs. The mixed-effects regression model was used for analysis of repeated measures of salt intake.
  
  
  RESULTS
  Mean age and salt intake for study participants at first participation in the survey were 56.5 ± 9.3 years and 12.8 ± 3.3 g/day in men and 55.8 ± 9.4 years and 10.6 ± 2.5 g/day in women, respectively. Mean energy intake decreased in men and women in all age groups from the first to fifth study waves. Eight-year longitudinal data showed that salt intake decreased in men. In stratified analyses by age, mean salt intake in men decreased 0.08 g/year among 40- to 49-year-olds, 0.09 g/year among 50- to 59-year-olds, 0.16 g/year among 60- to 69-year-olds, and 0.14 g/year among 70- to 79-year-olds. For women, mean salt intake decreased 0.08 g/year among 70- to 79-year-olds (P = 0.098). After adjusting for energy intake, salt intake was decreased among 60- to 69-year-old men (P = 0.049) and increased among 50- to 59-year-old women (P = 0.015).
  
  
  CONCLUSIONS
  Absolute salt intake was decreased among all age groups from 40 to 70 years in men and from 70 to 79 years in women. An increased focus on reducing energy intake resulted in only a modest decrease in salt intake. Although we observed a decline, salt intake still exceeded recommended levels. Efforts that focus on salt reduction are needed to address this important public health problem.
authors: Department for Development of Preventive Medicine, National Center for Geriatrics and Gerontology, Aichi, Japan. otsuka@ncgg.go.jp
authors: Rei
authors: R
authors: Otsuka
authors: Yuki
authors: Y
authors: Kato
authors: Tomoko
authors: T
authors: Imai
authors: Fujiko
authors: F
authors: Ando
authors: Hiroshi
authors: H
authors: Shimokata