Exercise as it relates to Disease/Effect of exercise on depression in an elderly population

What is the background to this research?

• The prevalence of depression has increased significantly over the past 50 years, and as a result, the World Health Organisation has predicted that by 2020 it will be surpassed only by cardiovascular disease as the leading cause of death and disability worldwide. Studies have found depression to be a strong risk factor for suicide, particularly in elderly populations. The natural changes associated with ageing make this population particularly vulnerable to developing depression. Such changes include increased loneliness, increased physical and mental disability and declines in cognitive function.
• There already exists a large amount of literature which demonstrates evidence of the positive effects of exercise on depression; however, according to this article, not a whole lot on how the various parameters of exercise, such as intensity and volume, can impact on these effects.
• Some evidence also exists regarding the disparities of depression prevalence between the two genders. Previous studies suggested higher depression scores exist in women than men, although further research is required.

Where is the research from?

• The study was conducted in Karlskrona, Sweden and included 860 local participants aged 60 years or older. The mean age of the participants was 75.3 years with a standard deviation of 10.0.
• The data for this study were collected between 2001 and 2003.
• One of the authors of the study, Magnus Lindwall, is a Professor of health psychology and has spent many years as a lecturer at various universities and institutions. The occupations of the other authors include physicians and more Professors of health psychology.
• The study was financed and supported by the Swedish Ministry of Health and Social Affairs, Blekinge Institute for Research and Development, and Halmstad University. It is unlikely that any bias exists within the results of the study as none of the groups mentioned make any commercial gains from services or products associated with the treatment of depression or exercise in general.

What kind of research was this?

• This was a cross-sectional study, as the population was only observed at one point in time.
• The research relied heavily on the use of the self-report which could present some problems in terms of it's reliability and validity.

What did the research involve?

• The participants took part in a survey, which consisted of two sets of two questions regarding their exercise status. They also each underwent a Montgomery Asberg Depression Rating Scale interview, which were conducted by trained interviewers to determine their current depression status. This scale usually consists of 10 items to be evaluated but one was removed for this study due to a discovered reliability weakness (i.e. only 9 items were considered). The first two exercise related questions were "How often did you exercise with light intensity in the last 12 months?" and "How often did you exercise more strenuously in the last 12 months?". The second set of questions determined their activity level greater than 12 months ago for the same two exercise intensities. There were four possible answers to these questions; "Never", "1-3 times per month", "Several times a week" or "Every day".
• Limitations include the use of self-report and also the cross-sectional design of the study. Because the study only measured data from the population at a specific point in time, the ability to infer either variable as the cause and the other as the effect is limited. Basically, it is difficult to say for certain whether it was the introduction of exercise that influenced depression status or whether it was the onset of depression that influenced exercise status. It is well known that the self-report approach can impact on the validity of a study, as interviewees may answer questions about themselves with bias. Questions regarding exercise would be particularly vulnerable to over-exaggerating participation. Furthermore, the study only included questions which could be interpreted as vague or misunderstood by the individual being interviewed. For example, some may consider jogging to be light exercise while to others it is perceived as strenuous. Finally, it does not include a "moderate intensity" category, which means the full range of exercise intensities are not considered and validity is once again at risk.
• All in all, this study is not overly valid for determining the effect on depression in response to the onset of regular exercise. What can be inferred confidently based on the setup of this study is whether or not a relationship exists between depression and exercise activity at different intensities and any differences between the two genders.

What were the basic results?

• The study found that the majority of participants were not clinically depressed; approximately 82% of men and 78% of women. For the majority of those that did show signs of depression, most were classified as only mild. Less than 2% of women and less than 1% of men were classified has having moderate or severe depression.
• In terms of activity levels it was discovered that men were more likely to be participating in all intensity levels of exercise. It was also found that younger individuals were more likely to be active than the older individuals.
• Age was found to be significantly correlated with depression scores for men but not for women.
• In general those with the lowest depression scores were also the ones who exercised several times a week. For men specifically, those who exercised strenuously everyday had the lowest depression scores.
• Finally, the results also indicated that those who had been inactive previously and switched to leading an active lifestyle had lower depression scores, and those that had switched from an active to an inactive lifestyle had higher depression scores.

What conclusions can we take from this research?

• The conclusions made by the authors of the article are that there is a high likelihood that a relationship exists between both light and strenuous intensity activities and lower depression scores in older adults, and also that women benefit most from exercising at a light intensity, whereas men benefit most from exercising at a strenuous intensity.
• The conclusions that I draw from the results of the study are slightly different. I agree with the first statement above; a relationship does seem to exist between an elderly individual's activity level and their depression score. However the second statement suggests that the authors can infer with certainty that the inclusion of exercise is affecting the individual's level of depression. Based on the cross-sectional design of the study, it doesn't seem as though this conclusion can be drawn as there is no definitive way to tell whether it was the onset of exercise that contributed to a lower depression score or whether the onset of depression affected the individual's physical activity pattern. All that can be concluded is that, generally, older women with lower depression scores exercise regularly at a light intensity, and that older men with lower depression scores exercise regularly at a strenuous intensity. While it is clear that a relationship exists between exercise intensity and depression, more research is needed to determine which factor is the cause and which is the effect before implementations can be constructed.

Practical advice

This article provides practical advice for general public, health practioners and also future researchers interested in this area of health.

• For those struggling with depression, the adoption of exercise on a daily or near-daily basis has a significant likelihood of decreasing the severity of depression's symptoms. Even if this amount of exercise cannot be achieved, remember that some is always better than none. Individuals can start by following the Australian Exercise Guidelines. For older people, this involves a mere 30 minutes of exercise per day, which is very achievable.

• For researchers interested in taking the next step and identifying whether it is exercise or depression which is the cause in the relationship they share, a study which resembles a controlled clinical trial may be useful. This may be the best approach, as it allows a control population (e.g. depressed persons who do not exercise) to be compared with an intervention population (e.g. depressed individuals who did not exercise previously, but undergo an exercise program for a duration of time) and then establish whether the introduction of exercise can help to abolish depressive symptoms in such individuals.

For those interested in more readings regarding exercise and it's effect on depression, the following resources may prove interesting:

• "Exercise for depression (Review)"
• "Regular exercise, anxiety, depression and personality: A population-based study"

For those who are seeking information, guidance, or support for either themselves or a loved one, here is a link to a helpful fact sheet provided by the Black Dog Institute on how to spot signs of depression and what to do next:

• Fact Sheet: Depression in Older People (available on their website)