As is the trend in many other countries, the Australian population is ageing. Mental health disorders especially depression are prevalent among older people and can cause serious adverse consequences. Antidepressant medications are the most commonly prescribed treatment option for managing depression in primary care, but are expensive, are slow to show results, require long-term adherence, and may cause serious adverse reactions among older people.

There is increasing interest in identifying and using alternative treatments for the prevention and management of depression. Existing evidence suggests an association between physical activity and depression. However, this area has been studied less among older people. Results of randomised controlled trials are inconsistent and many studies suffer methodological limitations. The aims of the three studies described in this thesis were to investigate the complex association between physical activity and depressive symptoms among older people through analysis of both quantitative and qualitative data. In public mental health, much effort is dedicated to treating depression, therefore, evidence-based preventive strategies intended to decrease the incidence of depression among community-dwelling older people is sparse. In this study, older people with depressive symptoms were targeted, subsyndromal depressive symptoms, as the most important risk indicator for developing clinical depression. The findings may not be generalisable to the older people with clinical depression, however, the findings can be important for identification of potential future prevention interventions.

Study 1 was a cross-sectional study that investigated the association between self-reported physical activity/walking and depressive symptoms among 420 adults aged 65 years and over who were recruited through general practice. The results of this study showed inactivity and depressive symptoms as prevalent problems among these community-dwelling older people. Analysis also showed significantly lower prevalence of physical activity/walking among older people with depressive symptoms. Additionally, after adjusting for the effect of potential confounding variables, this study found a significant negative association between walking and depressive symptoms among older people. This study found a significant negative association between physical activity and depressive symptom only in bivariate analyses (and not after adjusting for the effect of potential confounding variables in multivariate analyses). Since Study 1 used cross-sectional data, a definitive causal relationship between physical activity and depression could not be determined. Therefore, Study 2, a randomised controlled trial, undertaken to establish whether physical activity is causally related to depressive symptoms.

Study 2 was a single blind randomised controlled trial to investigate if a community-based physical activity program (which linked older people to increased social support and local physical activity resources) could significantly reduce depressive symptoms. The participants were 185 older people (mainly sedentary) who had participated in Study 1 and consented to participate in this trial. The intervention was conducted over six months and data were collected at baseline (T1), 3-month follow-up (T2) and 6-month follow-up (T3). Participants in the intervention group received a ‘Physical Activity Guide’ that included a carefully designed inventory of appropriate and accessible physical activity opportunities available in the local community and some general information about physical activity. Once a participant selected an activity, the project officer gave them the name of a specifically trained Physical Activity Motivator (PAM) associated with the activity. To increase the sustainability, the PAMs’ role also involved assisting participants to find an activity buddy who would continue to encourage and support them to maintain participation in the physical activity. They also received fortnightly or monthly telephone calls from the project officer. The participants in the control group only received the ‘Physical Activity Guide’. Data analyses were conducted using the whole sample and the depressed sample (participants with depressive symptoms at baseline). Surprisingly, physical activity/walking did not significantly increase in the intervention group and therefore most results were not as expected. However, there was a trend for a negative association between physical activity and depressive symptoms in both the control and intervention groups. Also, dose response analyses showed a trend for lower depressive symptoms among participants who increased their level of physical activity/walking compared to the participants who did not change their level of physical activity. This study provided recommendations regarding exercise programs for older adults. Similar to Study 1, this study was limited to using self-report tests for the measurement of physical activity/walking and using screening tests for physical activity, which must be considered when discussing the results. Even after this trial the problem of how physical activity can be useful for the management and prevention of depression among older people still remained. Therefore, Study 3 was conducted to identify barriers and facilitators to participation in physical activity among older people with depressive symptoms.

Study 3 was a qualitative study that aimed to further explore the barriers and facilitators to participation in physical activity among community-dwelling sedentary older people with depressive symptoms. The participants were 12 older people with depressive symptoms who attended Study 2. Data collection was conducted through face-to-face in-depth interviews. The results of this study reveal that participants had problems understanding the definition of physical activity, what is considered physical activity and how to carry out physical activity especially if suffering from health problems. Walking was the most common and preferred type of physical activity. The findings also suggest health problems and pain are the main barriers to participation in physical activity. Generally, different personal, social and environmental factors may stop or motivate older people from engaging in regular physical activity. Although depression did not emerge as a major barrier to participation in physical activity for the participants in this study, it may still be a possible barrier to physical activity for some individuals.

In conclusion, despite methodological limitations of these studies, such as using self-report measures, small sample size for some analyses, the present investigation provide insight into the negative association between physical activity and depressive symptoms among older people. The data collected has improved our understanding of the barriers and facilitators to participation in physical activity among older people with depressive symptoms. Consistent with the literature, the results show that using individually tailored physical activity programs can be more helpful for increasing the level of physical among older people compared to a ‘one-size-fits-all’ strategy. The present findings can be helpful for providing recommendations for future research and assist in the design of successful physical activity programs that meet the needs of older people with depressive symptoms.

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