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Puny teens run higher risk of early death, study finds

Effect similar to impact of excess weight and high blood pressure

Caroline White

Wednesday, 21 November 2012

Teens with low levels of muscular fitness carry a significantly greater risk of early death from several major causes in later life, suggests a large study published on bmj.com.

The effect is similar to well established risk factors for early death like overweight or high blood pressure, prompting the authors to call for young people to do some form of regular physical activity/exercise to boost their muscle power.

High body mass index (BMI) and high blood pressure at a young age are known risk factors for premature death, but whether muscular strength in childhood or adolescence can predict mortality is unclear.

A team of researchers from the Karolinska Institutet in Sweden tracked more than one million 16 to 19 year olds over a period of 24 years.

Participants underwent three reliable muscular strength tests at the start of the study: knee extension strength; handgrip strength; and elbow flexion strength. BMI and blood pressure were also measured. Premature death was defined as death before age of 55.

During the monitoring period, 26,145 participants (2.3% of the group) died. Suicide was the most common cause of death (22.3%) while 7.8% died of cardiovascular diseases or cancer (14.9%).

High levels of muscular fitness were associated with a 20-35% lower risk of early death from any cause and from cardiovascular diseases, independently of BMI or blood pressure. No association was seen between muscular strength and cancer deaths.

Stronger teens also had a 20-30% lower risk of early death from suicide and were up to 65% less likely to have any mental health problems, including schizophrenia and depression.

These results suggest that physically weaker individuals might be more mentally vulnerable, say the authors.

By contrast, young men with the lowest level of muscular strength showed the greatest risk of death from all causes and were more likely to die from cardiovascular disease or to commit suicide before the age of 55, the findings showed.

Death rates from any cause (per 100,000 person years) ranged between 122.3 and 86.9 for the weakest and strongest teens, respectively. Rates for cardiovascular disease were 9.5 and 5.6, respectively and 24.6 and 16.9, respectively, for suicide.

The authors say that low muscular strength in adolescents “is an emerging risk factor for major causes of death in young adulthood, such as suicide and cardiovascular diseases.” The effect sizes of these associations “are similar to classic risk factors such as body mass index and blood pressure,” they add.

They suggest that muscular strength tests, in particular handgrip strength, could be reliably assessed in schools and workplaces.

"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,” they say.

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