Regular physical activity is associated with reduced risk of fracture in postmenopausal women


Regular physical activity, including lighter intensity activities such as walking, is associated with reduced risk of hip and total fracture in postmenopausal women, according to new research from the University at Buffalo.

Published Oct. 25 in JAMA Network Open, the study is the most comprehensive evaluation of physical activity and fracture incidence in older women.

The study included more than 77,000 participants in the Women’s Health Initiative, who were followed up over 14 years. During follow-up, 33% of participants reported experiencing at least one fracture.

The women who did the highest amount of physical activity – which was approximately 35 minutes or more of daily recreational and household activities – had an 18% lower risk of hip fracture and 6% lower risk of total fracture.

The study is one more among several papers -all using data from the Women’s Health Initiative – published by UB researchers within the past few years that highlights the health benefits of being active, even at levels that are lower than the current physical activity guidelines.

“These findings provide evidence that fracture reduction is among the many positive attributes of regular physical activity in older women,” said Jean Wactawski-Wende, Ph.D., study co-author and dean of the University at Buffalo School of Public Health and Health Professions.

“Fracture is very common in postmenopausal women, and is associated with loss of independence, physical limitations and increased mortality,” Wactawski-Wende said.

In fact, the researchers note, approximately 1.5 million fractures occur in U.S. women each year, creating $12.7 billion in health care costs. About 14% of these fractures are in the hip. Mortality after a hip fracture is as high as 20%.

“Modest activities, including walking, can significantly reduce the risk of fracture, which can, in turn, lower the risk of death,” Wactawski-Wende said.

Non-recreation physical activity – examples include yardwork and household chores such as sweeping the floors or folding laundry—also was inversely associated with several types of fracture.

The research has important implications for public health, considering that these lighter intensity activities are common among older adults.

The main message, says study first author Michael LaMonte, Ph.D., research associate professor of epidemiology and environmental health at UB, is “sit less, move more, and every movement counts.”

According to the literature, the level of bone loss in a postmenopausal woman increases with age, respectively, with a loss of 0.6%, 1.1%, and 2.1% per year for the 60-69, 70-79, and> 80 age groups [1].

More precisely, the loss is 1.5% per year for the spine and 1.1% – 1.4% for the femoral neck in the first 4-5 years [2].

In the following years, the loss is less rapid as it is the immediate postmenopausal period characterized by a greater speed and entity of bone loss [3].

Although exercise is widely recommended as one of the primary preventive strategies to reduce the risk of osteoporosis [3], its effects on bone are controversial. In fact, not all types of exercise have the same positive effect on bone mineral density (BMD). While there is evidence that exercise induces an increase in bone mass in younger subjects, this effect in adults and elderly people remains questionable [4].

In elderly people, the results of the studies indicate that exercise may increase the thickness and resistance of cortical bone at loaded skeletal sites [5].

However, it seems that the improvement on bone strength induced by exercise in older adults is likely to be due to a lower loss of endocortical bone and/or an increase in tissue density, rather than an increase in bone size (periosteal apposition), typical of young subjects.

Supposing that trabecular bone architecture can adapt to increased loading, the effects of physical activity on thickness, number, separation, and orientation of trabecular elements in human bones are not known due to the limited resolution of most current commonly used imaging techniques [5].

Therefore, there is considerable interest in defining the adequate dosage and characteristics of exercises to improve bone strength in osteoporosis, in order to develop appropriate guidelines, given the fact that economic and social costs appear to be in a progressive and constant growth in relation to the aging of the population [67].

In the past years, many studies [1812] have reported very consistent results on the beneficial effects of exercise on BMD of the lumbar spine and the femur in menopausal women and, in general, in old age. Various exercises have been described to stimulate bone growth and preserve the bone mass; the optimal interventions are those favoring a mechanical stimulus on bone both through antigravity loading and the stress exerted on muscles [810]. In general, therapeutic exercises for osteoporosis can be ranked in two types of activities:

  1. Weight-bearing aerobic exercises, such as impact activities or any other exercise in which arms, feet, and legs are bearing the weight, (i.e., walking, stair climbing, jogging, volleyball, tennis and similar sports, Tai Chi, and dancing).
  2. Strength end/or resistance exercises, in which the joints are moved against some kind of resistance, in the form of free weights, machines, tubing, or one’s own body weight [9].

However, it is still not clear which exercise is the best suited and how long it would take to obtain an appropriate result. For example, the SIOMMS guidelines [13] recommend performing a minimum of physical activity, such as walking, for 30 minutes every day, despite the lack of available evidence. Meanwhile the position paper in the American College of Sports Medicine [5] suggests, during adulthood, to carry out weight-bearing endurance activities (i.e., tennis, stair climbing, and jogging), activities that involve jumping (volleyball, basketball), and resistance exercise (weight lifting) with moderate or high intensity, 3-5 times a week for 30-60 minutes, possibly in combination.

The effects of exercise on bone tissue have gained an important contribution also from studies on sport athletes. Numerous publications have linked physical exercise, bone metabolism markers, and bone mineral density [36]. While the isolated exercise (single bout training) seems to give a fleeting osteogenetic stimulation, a longer training, for example, 2 times a day for 5 weeks, seems to provide a better stimulation.

Furthermore, aerobic exercise seems to be particularly effective in the enzymatic activation of the osteoblasts. These observations underscore the importance of combining aerobic and anaerobic exercises in osteogenetic protocols.

Furthermore, after a longer period of training (6-12 months), the sedentary and untrained individuals obtained better results in BMD than the already trained individuals with significant osteogenetic activity without increasing the reabsorption indexes.

Probably individuals already trained with the continuation of exercise only maintained the good bone metabolic level already reached, which can not indefinitely increase. Regarding the type of exercise, sport shows us clearly how the activities performed in weight bearing, including high impact and endurance mechanical components, are more effective in increasing the BMD of limited or nonimpact exercises.

In fact, BMD is on average higher in athletes with sporting activities involving jumping (volleyball, basketball ball rugby, soccer, and martial arts) compared to those who do not have these mechanical characteristics, such as swimming, rowing, and cycling [36]. Furthermore there are evidences that high level of physical activity during youth, as seen in female athletes, seems to have a beneficial effect on bone mass and helps to prevent bone loss due to aging [37].

In clinical practice, however, the prescription of exercise in the elderly and osteoporotic patient must always be preceded by a careful evaluation: indeed, it is essential to define the type, intensity, and duration of a proposed program.

The decision is based on the subject’s muscle strength, range of motion, balance, gait, cardiopulmonary function, comorbidities, bone density, and history of previous fractures, as well as the risk of falling [123839]. In fact, the most intense exercises, such as high impact activities, that are effective in increasing bone mass in young subjects may not be indicated for some elderly osteoporotic subjects [40]. The progression of the exercise must always be respected, and, in patients with severe osteoporosis, the activities involving the flexion or rotation of the trunk must be avoided.

Regarding aquatic exercise, a recent systematic review supports the evidence of a trend showing its effectiveness in maintaining or even improving BMD [14].

More information: Michael J. LaMonte et al, Association of Physical Activity and Fracture Risk Among Postmenopausal Women, JAMA Network Open (2019). DOI: 10.1001/jamanetworkopen.2019.14084


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