Data from previous studies are inconsistent, and it is therefore uncertain whether, to what extent, and at what level leisure physical activity influences the risk of osteoporotic fractures in men.
Methods and Findings
A cohort of 2,205 men, 49–51 y of age, was enrolled in a longitudinal, population-based study. Leisure physical activity and other lifestyle habits were established at baseline and at ages 60, 70, 77, and 82 y. During 35 y of follow-up, 482 men had at least one fracture. Cox's proportional hazards regression was used to determine hazard ratios (HRs) of fracture associated with time-dependent physical activity habits and covariates. Men with a sedentary lifestyle (HR 2.56, 95% confidence interval 1.55–4.24) or men who walked or bicycled only for pleasure (HR 1.61, 95% confidence interval 1.10–2.36) had an increased adjusted risk of hip fracture compared with men who participated in regular sports activities for at least 3 h/wk. At the end of follow-up, 8.4% of the men with a high physical activity, 13.3% of the men with a medium physical activity, and 20.5% of the men with a low physical activity had suffered a hip fracture. According to the estimation of population-attributable risk, one third of all hip fractures could be prevented by participation in regular sports activities. High activity also conferred a reduced overall fracture risk.
Our data indicate that regular sports activities can reduce the risk of fractures in older men.
From a large cohort study with 35 years of follow-up, Michaelsson and colleagues conclude that regular sport activities can reduce the risk of fractures in older men.
One of the hazards of old age is that the bones become less dense—and therefore weaker—so when an elderly person falls, the result is often a broken bone. As many as half of all women and a quarter of men older than 50 y will break a bone because of this, and the consequences can be serious, particularly if the hip is broken. The thinning of bones, which is known as osteoporosis, does affect all people as they age, but the degree to which it occurs varies greatly between individuals. A priority area for medical research is finding ways in which osteoporosis can be reduced, with the aim of improving the lives of older people and reducing their risk of “osteoporotic fractures.” It is known that genetic and environmental factors can both play a part in how rapidly osteoporosis develops, but it is generally agreed that personal lifestyle factors are also important. Osteoporosis develops over many years; in most people bone density starts to decline after the age of about 30 y. Preventive action should therefore begin early.
Most research so far has focused on women, who are more at risk as the thinning of their bones increases after the menopause. (Indeed osteoporosis has sometimes been wrongly described as a “woman's disease.”) It is now accepted that women who are more physically active reduce the rate of decline in their bone density and, as a result, are less likely to break bones when they are elderly. There has been little research in men and the results have not been consistent.
Why Was This Study Done?
In order to provide better evidence as to whether men who do more physical activity have fewer osteoporotic fractures than those with lower activity levels, the researchers wanted to complete a study that was larger and was conducted over a longer period of time than previous research.
What Did the Researchers Do and Find?
Between 1970 and 1973, the researchers invited all those men living in Uppsala, Sweden, who were aged between 49 and 51 y to participate in a health survey. Most of them (2,205) agreed to do so. When the study began, they were asked questions about the amount of physical activity they took outside working hours. They were asked the same questions again when they were aged 60, 70, 77, and 82 y. A record was also kept of the number of fractures the men had suffered during the 35-y study period. (Although some of the men died before the end of the study, about half were still alive at the end.) On the basis of the answers to the questions on physical activity at the start of the study, the researchers divided the men into three categories: those whose lifestyle was considered to be “sedentary,” those whose leisure activities included some walking and cycling, and those who participated in sports for at least 3 h a week. These were referred to as the low, medium, and high activity groups. Over the 35-y period, 428 men had at least one fracture and 134 broke a hip, but there were big differences between the groups—20% of the low-activity men had fractures compared with 13% of those with medium activity and only 8% of those in the high-activity group. In particular, the chance of having a hip fracture was reduced by increased activity.
What Do These Findings Mean?
Taking exercise reduces the risk of an osteoporotic fracture. Participating in sports seems to be particularly effective; the researchers calculate that one-third of fractures could be prevented if men could be persuaded to take part in sports regularly. The researchers do note that the very best evidence always comes from studies where people are assigned at random to receive a particular “treatment” (in this case, it would be exercise) and are compared with others who did not receive the treatment. This is known as a “randomized controlled trial.” Such a trial would be difficult, if not impossible, to organize on this topic, and the approach adopted by the researchers, which is known as a “cohort study,” does provide very strong evidence. There are many other benefits from increased exercise (for example, in reducing the risk of heart attacks and strokes), and most governments are now promoting sports and other active leisure pursuits. This study adds further weight to support such policies.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0040199.g002.
There are many free sources of information about osteoporosis on the Web, and many organizations exist to support people with the condition. For example, the National Osteoporosis Society (UK) has useful information about the condition
In the USA, there is the Nationtal Osteoporosis Foundation (USA)
The equivalent organization in Australia is Osteoporosis Australia
The UK National Health Service's NHS Direct Health Encyclopedia has an entry on osteoporosis
MedlinePlus is an excellent source of information