Adolescent strength linked to early mortality risk

By Lynda Williams, Senior medwireNews Reporter

Muscle strength in adolescence is significantly associated with the likelihood for early death, reveal results from a large study of Swedish teenagers.

Analysis of data for 1,142,599 Swedish boys shows that those with the greatest knee extension and handgrip strengths at age 16 to 19 years were 20-35% less likely to die over 24 years of follow up than those with the weakest values, the researchers report in the BMJ.

In addition, the strongest adolescents had a 20-30% lower risk for suicide, and a 15-65% lower risk for being diagnosed with a psychiatric disorder, such as schizophrenia or a mood disorder.

"This study provides strong evidence that a low level of muscular strength in late adolescence… is associated with all-cause premature mortality to a similar extent as classic risk factors such as body mass index [BMI] or blood pressure," say Finn Rasmussen (Karolinska Institutet, Stockholm, Sweden) and co-authors.

The findings also suggest that "low muscular strength is associated with an increased risk of mortality due to suicide, supporting the notion that physically weaker people might also be mentally more vulnerable," they add.

In all, 26,145 of the participants died over the study, with suicide a more common cause of death than cardiovascular disease or cancer (22.3 vs 7.8 and 14.9%, respectively).

In particular, boys in the lowest decile for muscular strength had the highest rate of all-cause mortality, at 122.3 versus 86.9 cases per 100,000 person-years for boys in the highest decile for strength. This was true for deaths associated with both cardiovascular disease (9.5 vs 5.6 per 100,000 person-years) and suicide (24.6 vs 16.9 per 100,000 person-years).

Muscle strength was inversely associated with all-cause mortality regardless of whether boys were obese, overweight, normal weight, or underweight. BMI was the only significant influence on the risk for cancer-related mortality in the cohort, with a lower risk in those with a low versus high BMI.

"Although this study cannot disentangle causal pathways, physical training from childhood and adolescence seems to be needed," Rasmussen et al comment.

"People at increased risk of long term mortality, because of lower muscular strength, should be encouraged to engage in exercise programmes and other forms of physical activity."

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