Nationwide handgrip strength values and factors associated with muscle weakness in older adults: findings from the Brazilian Longitudinal Study of Aging (ELSI-Brazil).

Background: Handgrip strength (HGS) is a simple, quick, inexpensive, and highly reliable method for the assessment of muscle strength in clinical practice and epidemiological studies. This study aimed at describing the HGS values by age group and sex in Brazilians aged 50 years and over, determining age group- and sex-specific cutoff points for muscle weakness, and investigating sociodemographic and anthropometric variables associated with muscle weakness for each sex.

Methods: Data from the second wave of the Brazilian Longitudinal Study of Aging (ELSI-Brazil) were analyzed. HGS was measured in the dominant hand using a hydraulic hand dynamometer. Fractional polynomial regression models were fitted to estimate the percentiles (P5, P10, P20, P25, P50, P75, P90, and P95) of HGS by age group and sex. The P20 of the maximum HGS by age group and sex was used to define muscle weakness. Associations between sociodemographic (racial self-classification, place of residence, schooling, and monthly household income per capita in tertiles) and anthropometric variables (body mass index and waist circumference) and muscle weakness, by sex, were evaluated using logistic regression.

Results: The analytical sample included 7905 participants (63.1 ± 9.1 years; 60% women). HGS reduced with increasing age in both sexes. Men presented higher HGS than women in all age groups. The cutoff points for muscle weakness ranged from 28 to 15 kg for men and from 17 to 9 kg for women. In the adjusted analyses, low schooling (0-4 years) was positively associated with muscle weakness in both sexes (in men, odds ratio (OR) 2.45, 95% confidence interval (CI) 1.46-4.12; in women, OR 1.90, 95%CI 1.18-3.06). Low and middle monthly household income per capita also had a positive association with muscle weakness among women (OR 1.78, 95%CI 1.37-2.32; OR 1.32, 95%CI 1.01-1.73, respectively). Overweight had a negative association with muscle weakness among men (OR 0.66, 95%CI 0.52-0.83), and obesity was inversely associated with muscle weakness in both sexes (in men, OR 0.49, 95%CI 0.31-0.78; in women, OR 0.69, 95%CI 0.52-0.92).

Conclusions: This study provides HGS values and cutoff points for muscle weakness by age group and sex from a nationally representative sample of older Brazilian adults. The variables associated with muscle weakness slightly differed between men and women. HGS values and cutoff points generated can be used as benchmarks in clinical settings and foster future epidemiological research.