Decreased Grip Strength May Predict Risk for MI, Stroke: PURE Study

Deborah Brauser

May 14, 2015

HAMILTON, ON — Lack of muscle strength may point to an increased risk of a variety of detrimental outcomes (including CV- and non–CV-related death) in adults across the globe, suggest new findings from the Prospective Urban-Rural Epidemiology (PURE) study[1].

The current analysis of almost 140,000 adults from 17 countries showed highly significant inverse associations between grip strength and all-cause, CV, and non-CV mortality, as well as MI and stroke. In addition, grip strength was a significantly stronger predictor of all-cause mortality than was systolic blood pressure.

"We were surprised by the strength of the relationships found. Even when we took into account people's socioeconomic status, other health conditions, and level of education, we still found that the association between muscle strength and these various outcomes held," lead author Dr Darryl P Leong (McMaster University, Hamilton, ON), told heartwire from Medscape.

He added that grip strength could easily be measured in the office as a "risk-stratifying test"—especially in patients who have comorbidities. "Perhaps this test could identify patients who are particularly vulnerable to contracting illness of various sorts," said Leong.

The results were published online May 13, 2015 in the Lancet.

Tackling a Wider Patient Population

Leong noted that although past studies have shown an association between hand-grip strength and risk for death and CV disease, they have been mostly limited to high-income countries and/or with mostly white patient populations. "We felt these were important questions to ask in different people, because it's an inexpensive test and likely to be more useful in underresourced settings."

Between January 2003 and December 2009, the population-based PURE study enrolled 142,861 participants between the ages of 35 and 70 years from the following countries: Canada, Sweden, and United Arab Emirates (high income); Argentina, Brazil, Chile, Malaysia, Poland, South Africa, Turkey, China, Colombia, and Iran (middle income); and Bangladesh, India, Pakistan, and Zimbabwe (low income). The US was not included.

Demographic information was collected at baseline, as well as BP levels, body-mass index (BMI), and answers to the International Physical Activity Questionnaire (IPAQ) and food frequency questionnaires. The current analysis examined a cohort of 139,691 PURE participants who also had grip-strength measurements from a Jamar dynamometer.

At baseline, low grip strength was significantly linked to having CAD, heart failure, stroke, hypertension, or chronic obstructive pulmonary disease (COPD). A total of 2.4% of the cohort died within a median follow-up of 4 years. Of these, cause of death was known for 79%.

Significant associations were found at follow-up between weak grip strength and all-cause mortality (hazard ratio [HR] for every 5-kg decrease 1.16, P<0.0001); CV and non-CV mortality (HR 1.17 for both), and stroke (HR 1.09; all P<0.0001); as well as MI (HR 1.07, P =0.002). There was no significant association with incident diabetes.

These associations were similar across all countries included in the study. However, only the high-income countries also had a significant association between grip strength and cancer (P<0.0001).

Links between weak grip strength and all-cause and CV-related mortality remained significant for both sexes and across all ages.

Post hoc analysis showed that grip strength was a better predictor of death (HR 1.37, 95% CI 1.28–1.47) than systolic blood pressure (HR 1.15, 95% CI 1.10–1.21; both P<0.0001), but the latter was a better predictor of incident CV-related disease (HR 1.39 vs 1.21, respectively; both P<0.0001).

Both measures had an HR of 1.45 for predicting CV-related death (P<0.0001) and were significantly better predictors of this outcome, all-cause death, and incident CV-related disease vs measurements of physical-activity levels.

"In people of diverse economic and sociocultural backgrounds, grip strength is a strong predictor of cardiovascular mortality and a moderately strong predictor of incident cardiovascular disease," write the investigators.

Leong noted that exercise of any type should be recommended to all patients as part of a daily routine. "But our study strengthens the case that strength-building exercises and resistance training should be part of this and not just cardiorespiratory exercise."

Marker of Underlying Aging Process?

Dr Avan Aihie Sayer (University of Southampton, UK) and Thomas BL Kirkwood (Newcastle University, UK) write in an accompanying editorial that although grip strength has been shown before to be "a simple but powerful predictor of future disability, morbidity, and mortality," important questions have remained, especially if it's generalizable among a widely differing group of people[2].

"Poor muscle strength has been proposed to directly affect mortality through its association with increased disability. However, the findings from PURE suggest that associations with cardiovascular disease and its risk factors might be an additional pathway," they write.

Although the editorialists praise "the international breadth and methodological rigor" of the current analysis, they cite that its depth was lacking in some areas, including "the limitations of observational epidemiology" and that some of the associations deserve further investigation. They also note that the link between grip strength and cancer may have come about by chance.

Still, "loss of grip strength . . . might be a particularly good marker of underlying aging processes, perhaps because of the rarity of muscle-specific diseases contributing to change in muscle function," they write, adding that "linkage of epidemiological findings to new approaches in muscle biology could yield informative insights into the nature of human aging."

The main PURE study and its components are funded by independent, public sources around the world (details are in the report) and unrestricted grants from AstraZeneca, Sanofi, Boehringer Ingelheim, Servier, GlaxoSmithKline, Novartis, King Pharma, and the South Africa Sugar Association. Leong and coauthors, and the editorialists report no relevant financial relationships.

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