Compared to a general wellness programme, an 18-month exercise programme for older women improves bone mineral density and fall risk but has similar improvements in predicted coronary heart disease risk
- Correspondence to Graeme Jones
Menzies Research Institute, Private Bag 23, Hobart, Tasmania 7000, Australia;
Exercise and health
It is widely recognised that exercise is good for the prevention of a large number of illnesses. This conclusion has been drawn in large measure from observational studies that follow a group who choose to exercise and then compare them with a group who choose not to. This method can lead to a number of biases in terms of other health behaviours; for example, women who took hormone replacement therapy (HRT) were long thought to be protected against heart disease on the basis of observational studies, but a later randomised trial proved there was a higher heart attack risk with HRT, highlighting the value of the randomised trial design. Although there have been a number of trials, much uncertainty remains about what sort of exercise, how much and what intensity is necessary for optimal health. Individual exercise programmes are effective for blood pressure and cardiovascular disease risk1 or bone density.2 The challenge is to design a programme that has a global disease prevention effect.
The current study
This trial compared strength, balance and high-intensity activity at 70–85% maximum heart rate for 2 h 40 min per week with a low-intensity programme of 60 min per week at 50–60% maximum heart rate in 296 women from the general community with average fitness at baseline according to their estimated Vo2 max. Multiple outcome measures were used in this study, which has rarely been the case before. A high percentage of participants (>90%) reached final follow-up at 18 months, suggesting the study had high internal validity, but only an average of 75% of the subjects attended each session. There were small but significant differences in bone density at the hip and spine, in falls and in 10-year cardiovascular disease risk, mainly as a result of increases in high-density lipoprotein (HDL) cholesterol. The study was not powered for fractures, but these were twice as common in the control group, which is consistent with the findings of the Leisureworld study, where regular walking halved the risk of hip fracture.3 Healthcare costs were lower, but the difference did not reach significance. The control group improved their 10-year cardiovascular disease risk primarily as a result of decreased blood pressure.
The main problem with such studies is that it is often the motivated people who take part. In this study, 7500 invitation letters were sent out, 659 people replied, and, after screening, 296 were randomised (3.9% of those invited). This is likely to have been a very healthy group (even if they had average fitness), so it is uncertain whether the results can be generalised to non-institutionalised older women. Bone density and falls were two of the outcomes measured, but those most likely to benefit (women with osteoporosis) were excluded, and the average bone density was quite good among the participants at baseline. There remains no trial large enough to study end points such as fracture or heart attack directly. Such a trial is sorely needed.
With a complex combined programme it is difficult to know which component led to any observed improvement. One could hypothesise that the strength training improved bone density, the balance training improved falls risk, and vigorous activity improved HDL, but it is not possible to deconstruct this. The nice part is that the programme did deliver across a range of outcomes. The programme could be delivered in the community, but attendance was moderate even in a motivated group, so the challenge would be getting enough of the community to participate to achieve public health benefits. The other issue is ongoing participation, as it is likely that health benefits will be lost fairly quickly on cessation, especially for bone density.4 Nurse practitioners, exercise trainers and physiotherapists would be well placed to deliver such a programme and to encourage ongoing participation.