, new research suggests.
In a study of more than 115,000 adults, there was a significant association between stronger handgrip, up to 40 kg in men and 27 kg in women, and lower depression risk.
Investigators add that there was a “dose-response” association between physical strength and risk for depression.
“Being physically strong may serve as a preventive factor for depression in older adults, but this is limited to a maximum specific threshold for men and women,” Ruben Lopez-Bueno, PhD, of the department of physical medicine and nursing, University of Zaragoza, Spain, and colleagues write.
The findings were published online in the British Journal of Psychiatry.
Easy, fast, reliable
Depression is a major public health problem, and studies “aimed at examining preventive factors to tackle the increase in depression are required,” the investigators write.
They add that a “growing body of research” is examining the link between depression and muscle strength, with handgrip as an estimator, in healthy middle-aged and older adults.
Handgrip strength is an “easy-to-use, fast and reliable indicator of both sarcopenia (age-related loss of muscle mass) and dynapenia (age-related loss of muscle strength), both of which have been associated with depression,” the researchers note.
It is plausible that there is a “regulatory role of skeletal muscle on brain function affecting this condition,” they add.
They note that exercise seems to play a “key role” because it can improve muscle strength as well as muscle mass, downregulate systemic inflammation, and improve neuroplasticity, neuroendocrine, and oxidative stress responses.
Previous studies have relied either on cross-sectional or prospective cohort models and have focused mostly on a specific country, “not accounting for time-varying changes of both handgrip strength and relevant covariables.”
Moreover, previous evidence has been mixed regarding the “extent to which handgrip strength levels may associate with lower risk of depression, with study results ranging from weak to strong associations,” the investigators write.
So “higher-quality research with representative samples from different countries is required to better clarify the strength of such an association and to confirm directionality,” they add.
To fill this gap, the researchers turned to data from waves 1, 2, 4, 5, 6, and 7 of the Survey of Health, Ageing and Retirement in Europe (SHARE). This encompassed 115,601 individuals aged 50 years and older (mean age, 64.3 years; 54.3% women) residing in European countries and Israel (24 countries total).
Data from wave 3 were not used because handgrip measures were not used in that wave. In the other waves, a handheld dynamometer was used to measure handgrip strength.
The participants were divided into tertiles of handgrip strength, with the “first third” being the lowest tertile of strength and the “final third” representing the highest strength.
All participants were followed for a median of 7.3 years (792,459 person-years), during which 26.1% experienced a risk for depression, as reflected by scores on the EURO-D 12-item scale.
The investigators set the time scale as the months from study entry until either a first depression onset or the end of follow-up.
Covariates that the researchers accounted for included gender, age, education, country, body mass index, physical inactivity, smoking, alcohol consumption, whether living with a partner, wave of inclusion, chronic diseases, consumption of prescribed drugs, and fruit and vegetable consumption.
The researchers used two models: the first adjusted for gender and age at time of the interview, and the second adjusted for all confounders.
In the model that was adjusted only for gender and age, greater handgrip strength was associated with a significantly reduced risk for depression among participants in the second, third, and the final third in comparison with the first third (hazard ratio, 0.65; 95% confidence interval, 0.63-0.68; and HR, 0.50; 95% CI, 0.48-0.53, respectively).
The associations remained consistent in the fully adjusted model, although risk for depression was slightly attenuated in the second and final thirds compared with the first third (HR, 0.76; 95% CI, 0.71-0.81; and HR, 0.64; 95% CI, 0.59-0.69, respectively).
When the researchers conducted analyses using restricted cubic spline modeling, they found a significant association for each kilogram increase of handgrip strength and depression, up to 40 kg in men and 27 kg in women (HR, 1.39; 95% CI, 1.08-1.71; and HR, 1.28; 95% CI, 1.05-1.55, respectively).
There was no greater reduction in depression risk in those with handgrip strength above those values.