Exercise as it relates to Disease/Effects of exercise on bone mineral density

Effects of exercise on bone mineral density



What is the background to this research?
Among the elderly, bone mineral density (BMD) is an ever increasing health concern. In 1990, the number of hip fractures occurring each year was estimated at approximately 1.25 million world wide, with females being three times more likely to suffer from an incident. Gullberg (1997) estimated a significant increase of up to 310% in the fracture numbers by 2025. Ageing is linked to a decreased osteoblast activity and an increase in osteoclast activity. This is attributed to a relative decline in hormones favouring local expression of molecules such as interleukins and TNF-α. The result is a decrease in skeletal tissue, causing bones to become weaker and commonly leading to osteoporosis. Hip and vertebral fractures cause serious complications in the form of an impaired quality of life, disability, chronic pain and premature death. Hip fractures caused by falls increases women mortality by 12-20% within the first year post incident. Additionally, there is an economic burden due to the injuries suffered from falls. Between 2006 and 2007, the estimated cost of falls related injuries to the New South Wales healthcare system has been calculated at over $558 million. Due to the impact fractures have on the public and economy, significant research has been conducted in an attempt to find ways of increasing bone mineral density. The effects of exercise on BMD has been extensively studied, as repeated mechanical loading has been theorised to increase the cross sectional area of certain bones. This lead to researchers reviewing the literature and summarising the results of the relevant articles.

Where is the research from and what structure did they follow?
The meta-analysis of the literature was conducted by researchers from the University of Porto's Research Centre in Physical Activity, Health and Leisure in Portugal. The project was funded by grants from the Portuguese Foundation of Science and Technology along with other independent grants. The article was reviewed and published online by The American Ageing Association in 2011.

The research was conducted as a meta-analysis of randomised control trials (RCT) with a specific range of acceptable criteria. The meta-analysis was specifically looking at RCT that investigated the effects of exercise interventions on femoral neck (FN) and lumbar spine (LS) BMD. Due to the strict criteria for acceptable studies, papers that were published in another language were not accepted to avoid translation errors. Studies that focused on specific races or ethnic groups were also excluded.

What did the research involve?
The aim of the meta-analysis was to assess the effects of exercise interventions, with different impact loading characteristics, on lumbar spine and femoral neck bone mineral density in older adults (in this instance defined as over 60 years old). The researchers narrowed their focus to weight bearing exercises such as aerobics, resistance training, endurance training, circuit training, jogging, jumping and any other modalities that create an impact on the skeleton. Studies that included pharmaceutical interventions or treatments known to improve BMD were excluded. The strict criteria restricted the number of acceptable studies, however this provided a set of data with little to no unpredictable variables.

The meta-analysis had seven specific inclusion criterion that each study needed to comply with; the criteria included The data was extracted using a coding framework that screened for multiple variables including but not limited too sample size, attrition, follow up length and compliance.
 * 1 Be exclusively RCT's
 * 2 Exercise was the only intervention applied
 * 3 Older adults aged ≥60 years or whose mean age is ≥65 years
 * 4 Data for one or more of the following variables provided; lumbar spine BMD and femoral neck BMD
 * 5 Studies were published in English language journals,
 * 6 A control group was assigned for comparative purposes
 * 7 The exercise intervention lasted a minimum of 16 weeks.

What were the basic results and how did the researchers interpret the findings?
Out of the 19 acceptable studies, researchers found a significant increase in mean BMD of 0.011g/cm2 for the lumbar spine, and 0.016g/cm2 at femoral neck. Results relating to combined loading strategies on FN were moderately inconsistent, conversely, LS data remained consistent throughout the review. Studies which consisted of resistance exercise as the primary intervention resulted in consistent data, however their results were not significant.

The researchers concluded that exercise intervention with an emphasis on impact activities such as walking and stair climbing result in a significant increase in BMD. Although the other interventions proved to be effective in preventing and increasing BMD, the results were not significant.

What conclusions should be taken away from this research?
The current American College of Sports Medicine's (ACSM) position stand on exercise and physical activity for older adults concludes that age related declines in BMD can be counteracted by engaging in aerobic exercise. These conclusions came from significant evidence into the effects of exercise on BMD in pre-menopausal and post-menopausal women. With the addition of the current meta-analysis, this position stand can be extrapolated to all older adults regardless of sex. When proscribing an exercise intervention for older adults with BMD problems, moderate to high impact exercises are the most effective treatment. However, the psychological and physiological benefits from resistance training and low impact activities shouldn't be overlooked as they promote a healthy quality of life.

What are the implications of this research?
The research confirmed the previous understanding of how exercise effects BMD. It also extrapolated the results to cover males and older adults of greater ages. The results provide clinicians with significant clinical evidence for the application of impact based exercises as a treatment for chronic conditions such as osteoporosis. With this information, medical professionals can more effectively treat patients with less invasive procedures and simple lifestyle changes. The risks associated with treatment and the financial burden placed on the economy is also significantly decreased. In conclusion, the results from the meta-analysis surmise that exercise can be an effective treatment for older adults with a chronic BMD issues. However more research is required on varying ethnic groups in order to definitively recommend exercise across racial groups.