Can your grip and your walk predict when you'll die?
Background Several studies in older people have shown that grip strength predicts all-cause mortality. The mechanisms are unclear. Muscle strength declines with age, accompanied by a loss of muscle mass and an increase in fat, but the role that body composition plays in the association between grip strength and mortality has been little explored. We investigated the relation between grip strength, body composition, and cause-specific and total mortality in 800 men and women aged 65 and over.
Methods During 197374 the UK Department of Health and Social Security surveyed random samples of men and women aged 65 and over living in eight areas of Britain to assess the nutritional state of the elderly population. The survey included a clinical examination by a geriatrician who assessed grip strength and anthropometry. We used Cox proportional hazards models to examine mortality over 24 years of follow-up.
Results Poorer grip strength was associated with increased mortality from all-causes, from cardiovascular disease, and from cancer in men, though not in women. After adjustment for potential confounding factors, including arm muscle area and BMI, the relative risk of death in men was 0.81 (95% CI 0.700.95) from all-causes, 0.73 (95% CI 0.600.89) from cardiovascular disease, and 0.81 (95% CI 0.660.98) from cancer per SD increase in grip strength. These associations remained statistically significant after further adjustment for fat-free mass or % body fat.
Conclusion Grip strength is a long-term predictor of mortality from all-causes, cardiovascular disease, and cancer in men. Muscle size and other indicators of body composition did not explain these associations.
Source: "Grip strength, body composition, and mortality" from International Journal of Epidemiology 2007 36(1):228-235
And:
The study examined whether a test of walking speed provides similar predictive information on mortality risk as does a summary measure of lower body function. Data were from the Hispanic Established Population for the Epidemiologic Study of the Elderly database and included Mexican Americans aged 65 years or more (1993–2000). Primary measures included a short physical performance battery, a test of walking speed, and mortality. The average age of the sample was 72.0 years, and 58.3 percent were women. The observed hazard ratio of mortality risk was similar for the full short physical performance battery and walking speed alone, in both unadjusted and adjusted baseline models. A time-dependent walking speed measure showed a more than twofold increased risk of mortality for individuals categorized with slower walking speed. The results also showed a linear association between continuous walking speed and mortality with and without adjustment for baseline covariates. This study provides evidence that walking speed alone can provide similar information on mortality risk as does a more comprehensive summary measure of physical performance. Because walking speed is a quick and easy-to-administer test, findings have implications for clinical use, especially among underserved minority groups where cultural and language barriers may exist.
Source: "Measures of Lower Body Function and Risk of Mortality over 7 Years of Follow-up" from American Journal of Epidemiology 2007 166(5):599-605
Bonus - Guys, if your sperm are healthy, you're probably healthy too:
Fertility status may predict later mortality, but no studies have examined the effect of semen quality on subsequent mortality. Men referred to the Copenhagen Sperm Analysis Laboratory by general practitioners and urologists from 1963 to 2001 were, through a unique personal identification number, linked to the Danish central registers that hold information on all cases of cancer, causes of death, and number of children in the Danish population. The men were followed until December 31, 2001, death, or censoring, whichever occurred first, and the total mortality and cause-specific mortality of the cohort were compared with those of all age-standardized Danish men or according to semen characteristics. Among 43,277 men without azospermia referred for infertility problems, mortality decreased as the sperm concentration increased up to a threshold of 40 million/mL. As the percentages of motile and morphologically normal spermatozoa and semen volume increased, mortality decreased in a dose-response manner (Ptrend < 0.05). The decrease in mortality among men with good semen quality was due to a decrease in a wide range of diseases and was found among men both with and without children; therefore, the decrease in mortality could not be attributed solely to lifestyle and/or social factors. Semen quality may therefore be a fundamental biomarker of overall male health.
Source: "Good Semen Quality and Life Expectancy: A Cohort Study of 43,277 Men" from American Journal of Epidemiology 2009 170(5):559-565
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