Muscular Strength and Adiposity as Predictors of Adulthood Cancer Mortality in Men (CEBP)

On January 7, 2013 by Physical Culturist

Summary of study by: CBASS

We already have good evidence that aerobic fitness lessens cancer risk; see the Miracle of Movement http://www.cbass.com/MiracleMovement.htm . We also know the overweight kills: http://www.cbass.com/Overweightkills.htm . This study and the earlier analysis by the same researchers cast a new light on muscular strength as a major predictor of cancer mortality. Both studies, led by Jonatan R. Ruiz of the Department of Biosciences and Nutrition at the Karolinska Institute in Hudding, Sweden, utilized data collected at the Cooper Clinic in Dallas, Texas, and incorporated into the Aerobic Center Longitudinal Study (ACLS). The new study by Ruiz and colleagues is reported in Cancer Epidemiology, Biomarkers & Prevention (May 2009).

The study involved 8,677 men (age 20 to 80) who received comprehensive medical exams, including muscular strength and aerobic fitness testing, at the Cooper Clinic between 1980 and 1989. Body composition was also measured as part of the exam. During an average follow-up period of 18.9 years (ending December 31, 2003), 503 of the men died, 199 from cancer and 145 from cardiovascular disease. (Dr. Cooper has told me that I am enrolled in the ongoing ACLS.)

Muscular strength in the upper and lower body was tested using one-rep maximum in the bench press and leg press. Cardiovascular fitness was measured with a maximal treadmill test. In both categories, the men were divided into three equal groups based on age-specific performance. Men with the best performance were placed in the top third, the men with the poorest performance in the bottom third, with those in between in the middle third.

The stated purpose of the study was to examine the associations between muscular strength, overall and waistline fatness, and cancer deaths.

Here is the primary conclusion:

Higher levels of muscular strength are associated with lower cancer mortality risk in men, independent of…overall and central adiposity, and other potential confounders.

There’s more to it than that, however.

The details are quite enlightening for anyone interested in living a long and healthy life. The particulars are a bit mind-numbing, but the end result is clear as a bell.

There were three main findings on strength, fatness and cancer mortality.

First, muscular strength was significantly and inversely associated with cancer mortality; men in the moderate and high strength category had about 37% fewer cancer deaths than those in the lowest strength category. This association remained after adjustment for overall and waistline fatness, and for cardiovascular fitness.

Secondly, percent body fat was positively associated with rates of cancer mortality; higher body fat was associated with higher rates of cancer deaths. This association, however, did not persist after adjustment for muscular strength or cardiovascular fitness. In other words, higher strength and fitness appear to substantially override higher body fat.

Third, a combination of muscular strength and fatness is powerfully associated with cancer death; men in the lowest third for muscular strength with high levels of fatness have a 40% to 50% higher rate of cancer death than obese men with at least moderate (middle third) muscular strength. In short, a moderate level of muscular strength helps a lot if you are obese.

Taken together, these findings indicate that having at least moderate age-adjusted levels of muscular strength may counteract the deleterious consequences attributed to adiposity,” the report stated. “Efforts should then focus not only on reducing levels of adiposity but also on increasing the muscular strength level. (Emphasis mine)

Now we shift focus to cardiovascular fitness. Listen to what Ruiz and his colleagues say about the importance of aerobic fitness:

Higher levels of cardiorespiratory fitness are strongly associated with lower risk of cancer mortality in men and women, young or older people, and in diabetic or nondiabetic persons, independently of their weight status and tobacco use.

Clearly, aerobic fitness has a powerful effect on cancer risk.

The Ruiz report says men who were strong but unfit were at appreciably higher risk than men who were strong and fit.

(This is important!) The study found that muscular strength and cardiorespiratory fitness were only “moderately correlated.” This suggests that the associations between the two forms of fitness and cancer risk involve “different mechanisms.” Both strength and aerobic fitness appear to have profound and independent effects on cancer risk. A combination of the two forms of fitness, working together, would appear to be most protective—and that’s what the study found.

Age-adjusted death rate in men with high levels of both muscular strength and cardiovascular fitness was 60% lower than the death rate in unfit men with the lowest level of muscular strength. Unquestionably, it pays to be both strong and fit.

The Ruiz report lists a number of “plausible mechanisms” that may explain the independent protective benefits of higher levels of muscular strength. They include: “regulation in the metabolism of insulin, and insulin-like growth factors…, reduced exposure to systemic inflammation, sex hormones, improved antioxidant defense and immune function, and reduced overall and central adiposity.”

The take-home message from Ruiz and his colleagues is loud and clear:

Maintaining a healthy weight should continue to be a cornerstone in the prevention of chronic disease and premature death….It is equally important to maintain healthy muscular strength levels, and, most importantly, to prevent falling into the lower strength categories.

They suggest regular resistance training involving the major muscle groups of the upper and lower body at least two days per week.

Resistance and aerobic exercise should complement each other. (My emphasis)


Below is the referenced study from PUBMED:
(click here to view the entire study by CEBP)

Cancer Epidemiol Biomarkers Prev. 2009 May;18(5):1468-76. Epub 2009 Apr 14.

Muscular strength and adiposity as predictors of adulthood cancer mortality in men.

Source

Department of Biosciences and Nutrition, Karolinska Institutet, Sweden. ruizj@ugr.es

Abstract

BACKGROUND:

We examined the associations between muscular strength, markers of overall and central adiposity, and cancer mortality in men.

METHODS:

A prospective cohort study including 8,677 men ages 20 to 82 years followed from 1980 to 2003. Participants were enrolled in The Aerobics Centre Longitudinal Study, the Cooper Institute in Dallas, Texas. Muscular strength was quantified by combining 1-repetition maximal measures for leg and bench presses. Adiposity was assessed by body mass index (BMI), percent body fat, and waist circumference.

RESULTS:

Cancer death rates per 10,000 person-years adjusted for age and examination year were 17.5, 11.0, and 10.3 across incremental thirds of muscular strength (P = 0.001); 10.9, 13.4, and 20.1 across BMI groups of 18.5-24.9, 25.0-29.9, and > or =30 kg/m(2), respectively (P = 0.008); 11.6 and 17.5 for normal (<25%) and high percent body fat (> or =25%), respectively (P = 0.006); and 12.2 and 16.7 for normal (< or =102 cm) and high waist circumference (>102 cm), respectively (P = 0.06). After adjusting for additional potential confounders, hazard ratios (95% confidence intervals) were 1.00 (reference), 0.65 (0.47-0.90), and 0.61 (0.44-0.85) across incremental thirds of muscular strength, respectively (P = 0.003 for linear trend). Further adjustment for BMI, percent body fat, waist circumference, or cardiorespiratory fitness had little effect on the association. The associations of BMI, percent body fat, or waist circumference with cancer mortality did not persist after further adjusting for muscular strength (all P > or = 0.1).

CONCLUSIONS:

Higher levels of muscular strength are associated with lower cancer mortality risk in men, independent of clinically established measures of overall and central adiposity, and other potential confounders.

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