There are several different components of physical fitness; these include cardiorespiratory (aerobic) fitness, muscular strength, flexibility, and body weight status (e.g., BMI, percent body fat).
Over the past few decades, it has become indisputable that higher levels of cardiorespiratory fitness are strongly related to a decreased risk of several adverse health outcomes. These include heart attack, stroke, heart failure, sudden cardiac death, some cancers, type 2 diabetes, chronic kidney disease, and dementia. While obesity continues to be a major public health issue, Cooper Institute studies have consistently shown that most of the health risks that are associated with obesity are decreased by having a moderate or high level of cardiorespiratory fitness.
In recent years, there has been increased interest in muscular strength as a predictor of health outcomes. A quick, simple, and inexpensive method of assessing this physical fitness component is by using a handgrip strength measure. While there have been published studies of handgrip strength and future health outcomes, the vast majority of these studies have been done using samples from high-income countries. Results have shown that reduced handgrip strength is related to an increased risk of all-cause and cardiovascular disease mortality. Much less is known regarding the relationship between handgrip strength and health outcomes among low or middle-income countries.
To that end, we will now discuss an important study published in The Lancet a few years ago.
The Prospective Urban-Rural Epidemiology (PURE) study included individuals from 17 countries with widely varied socioeconomic status*. A total of 139,691 subjects were enrolled (58,652 men and 81,039 women); all were between the ages of 35 and 70 years. Detailed questionnaires and measurements were used during the baseline period of data collection (2003 through 2009). Among the measures used in the study was handgrip strength using a Jamar© handgrip dynamometer. Three measurements were taken from both hands of each participant; the maximal value from each hand was used in the analyses.
The researchers then examined the relationship between grip strength and risk of several health outcomes including all-cause death, cardiovascular death, heart attack, stroke, diabetes, hospital admission for pneumonia, asthma, tuberculosis, and chronic obstructive pulmonary disease (COPD), as well as fractures, and injuries due to a fall. During the data analysis phase, the researchers carefully took into account several factors that might have influenced the results. These included age, sex, smoking, alcohol intake, BMI, education level, dietary intake, employment status, physical activity level, and any health conditions (e.g., previous heart attack, stroke, etc.) that were present at baseline.
Following data collection, participants were grouped into thirds (low strength, moderate strength, high strength) for each age and sex group based on their grip strength scores. Significant predictors of high grip strength included younger age, male sex, high level of education, high level of physical activity, sufficient total calorie and protein intake, and higher values for height and weight. During an average of 4 years of follow-up, 3379 of the participants died, and several thousand others experienced non-fatal outcomes such as heart attack, stroke, and the other previously mentioned events. When compared to those who were the strongest in the same age and sex group, each 5 kg decrement in baseline grip strength was related to the following risks during the follow-up period.
- 16% increased risk of all-cause mortality
- 17% increased risk of cardiovascular disease mortality
- 17% increased risk of non-cardiovascular disease mortality
- 7% increased risk of heart attack
- 9% increased risk of stroke
All of the risks reported above were statistically significant, meaning that these results were extremely unlikely to be due just to chance. During the follow-up, there was no significant relationship between baseline handgrip strength and risk of hospital admission for pneumonia, asthma, tuberculosis, and chronic obstructive pulmonary disease. Nor was there a significant relationship of baseline handgrip strength with diabetes, fractures, or injuries due to a fall during follow-up. This last finding can likely be explained by the fact that poor lower body strength is related to increased risk of falls. Handgrip strength is more closely related to upper body strength than lower body strength.
Among individuals who experienced non-fatal events such as heart attack, stroke, pneumonia, COPD, or cancer diagnosis during follow-up, higher levels of handgrip strength were related to a substantially reduced risk of death following the event, even after taking into account the many factors that could have influenced the results.
So, in this large study with an extraordinarily diverse sample, a simple measure of handgrip strength was significantly related to a number of future health outcomes.
How does handgrip strength relate to a reduced risk of some types of illness and death
The authors of this study acknowledged that their findings did not prove cause and effect. They suggested that part of the reason for their findings was that those with higher levels of grip strength are likely to have less stiff and more healthy arteries, reducing the likelihood of fatty plaque development. This in turn might lead to a decreased risk of cardiovascular events, including cardiovascular death. The researchers also suggested that individuals with higher levels of grip strength might have lower levels of inflammation than those with lower levels of grip strength.
Without a doubt, further studies are needed in order to establish the exact mechanisms by which handgrip strength is related to health outcomes. Nevertheless, these findings help to reinforce the current Physical Activity Guidelines for Americans, which include a recommendation that whole-body resistance training should be performed at least two days each week.
Leong, D.P., et al. (2015). Prognostic value of grip strength: finding from the PURE study. The Lancet. 386:266-273.
*High-income countries: Canada, Sweden, United Arab Emirates. Upper middle-income countries: Argentina, Brazil, Chile, Malaysia, Poland, South Africa, Turkey. Lower middle-income countries: China, Colombia, Iran. Low-income countries: Bangladesh, India, Pakistan, Zimbabwe