Temporal trends in handgrip strength for older Japanese adults between 1998 and 2017

Abstract

Objective: to estimate temporal trends in handgrip strength (HGS) for older Japanese adults between 1998 and 2017.

Design and methods: adults aged 60-79 years were included. Annual nationally representative HGS data (n = 176,449) for the 19-year study period were obtained from the Japanese Ministry of Education, Culture, Sports, Science and Technology. Temporal trends in mean HGS were estimated by sample-weighted regression models relating the year of testing to mean HGS. National trends in absolute, percent and standardised HGS were estimated by a post-stratified population-weighting procedure. Temporal trends in variability were estimated as the ratio of coefficients of variation (CVs).

Results: collectively, there was a small improvement in mean HGS of 1.4 kg (95% confidence interval [CI]: 1.3-1.5), 4.5% (95%CI: 4.3-4.7) or 0.27 standard deviations (95%CI: 0.26-0.28) between 1998 and 2017. The rate of improvement progressively increased over time, with more recent values (post-2008) 1.5-fold larger than earlier values. Gender- and age-related temporal differences were negligible. Variability in HGS declined substantially over time (ratio of CVs [95%CI]: 0.88 [0.86-0.90]), with declines 1.9-fold larger in women compared to men and 1.7-fold larger in 70- to 79-year-olds compared to 60- to 69-year-olds.

Conclusions: there has been a small, progressive improvement in mean HGS for older Japanese adults since 1998, which is suggestive of a corresponding improvement in strength capacity. The substantial decline in variability indicates that the improvement in mean HGS was not uniform across the population.

Keywords: aged; fitness testing; muscle strength; older people; physical fitness; secular changes.