Low muscle strength in adolescence is strongly associated with a greater risk of premature death, according to a study.
The report calls for young people, particularly those with very low strength, to engage in regular physical activity to boost muscular fitness to avoid an early death.
High body mass index (BMI) and high blood pressure at a young age are known risk factors for premature death from several major causes, but whether muscular strength in childhood or adolescence can predict mortality is unclear.
A team of researchers from Sweden tracked more than one million Swedish male adolescents aged 16 to 19 over a period of 24 years.
Participants in the study, published in the British Medical Journal, underwent three muscular strength tests; knee extension strength, handgrip strength and elbow flexion strength, with premature death being defined as before 55 years.
During the follow-up period, 26,145 participants, or 2.3% of the group died, with suicide, 22.3%, the most common cause, compared with cancer, 14.9%, and cardiovascular diseases, 7.8%.
Researchers said muscular strength was associated with a 20-35% lower risk of early death from any cause and also from cardiovascular diseases, independently of BMI or blood pressure. No association was seen with cancer deaths.
However, there was no indication that muscle-building exercises will help individuals live longer. Physical strength is an indication of physical resilience and cardiovascular fitness, often associated with higher mortality rates, as opposed to weaker muscular strength.
The study also did not explain whether the physical weakness was caused by or resulted from ill health.
The report found that stronger adolescents had a 20-30% lower risk of early death from suicide and were up to 65% less likely to have any psychiatric diagnosis, such as schizophrenia and mood disorders.
These reports suggests that the results indicate that physically weaker individuals might be more mentally vulnerable.
In contrast, male adolescents with the lowest level of muscular strength showed the greatest all-cause mortality and also the greatest mortality in cardiovascular disease and suicide before the age of 55.
Death rates from any cause (per 100,000 person years) ranged between 122.3 and 86.9 for weakest and strongest adolescents respectively. Rates for cardiovascular diseases were 9.5 and 5.6 and for suicide were 24.6 and 16.9.
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.