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What did I do? Aims of your PhD
My doctoral work aimed to advance understanding of the interactions between physical activity, falls and physical function from mid-life to older age. My PhD involved seven papers written over four years. Figure 1 overviews the designs and results of studies included in the thesis.
Overview of studies included in the thesis. ALSWH, Australian Longitudinal Study on Women’s Health.
Why did I do it? Rationale for your PhD
Witnessing my grandma’s fall, hip fracture and subsequent rehabilitation made me realise the severe consequences of falls on older adults’ health and function, and the emotional and practical strain on older adults and their families. One in three older adults has at least one fall each year, and the number of falls increases with age. The WHO recommends adults undertake at least 150–300 min/week of moderate-intensity physical activity. Yet, one in three older adults is physically inactive globally, highlighting the need to better understand adherence to exercise and physical activity. Structured exercises (a form of physical activity) targeting balance, function and strength reduce falls in older adults in multiple trials.1 However, trial follow-up periods are short and have limited statistical power to investigate physical activity participation, frailty and fall-related injuries. Existing evidence also often examines either falls regardless of injuries or injurious falls alone. Therefore, my PhD has rigorously examined both short-term and long-term links between physical activity participation, falls, fall-related injuries and physical function, addressing overlooked and underexplored areas in the existing literature.
How did we do it? Brief overview of main methods
Study One2 analysed adherence and use of behaviour change techniques in 102 trials of fall prevention exercise and examined the association between participants’ characteristics, intervention components and adherence to exercise intervention using secondary analysis of a systematic review. Studies Two to Seven were achieved through a large representative longitudinal study of middle-aged (n=13 714) and older (n=12 432) women in the Australian Longitudinal Study on Women’s Health. Relationships were examined within a causal framework from directed acyclic graphs. Study Two3 examined physical activity participation and falls in two cohorts of older Australian women born 20 years apart. Study Three4 examined prospective associations between amounts and types of physical activity participation and falls in women of older age (aged 65–70 years). Study Four5 explored associations between physical activity participation and injurious falls and examined effect modification by physical function limitation and frailty in cross-sectional and prospective analyses. Study Five6 analysed patterns of physical activity participation from mid-life to older age over an 18-year period using repeated-measures latent class analysis, and the associations with falls in older age were analysed using multinomial logistic regression. Studies Six and Seven7 8 examined longitudinal patterns of falls and physical activity participation from mid-life to older age; and bidirectional prospective associations between physical activity and falls, and physical activity and physical function at multiple time points with 3 year intervals from mid-life to older age using generalised estimating equations.
What did we find? Overview of main findings
Study One:2 higher adherence to exercise was observed in interventions that were shorter, did not include prescribed home exercise, had more weekly sessions and used fewer behaviour change techniques. Participant characteristics (age, sex, fall risk) were not associated with adherence. Study Two:3 women in the cohort born later were more physically active, more likely to fall, but similar proportions reported injurious falls. Physical activity participation was associated with fewer non-injurious and injurious falls cross-sectionally in both cohorts, at a similar age. Study Three:4 participation in moderate-intensity and vigorous-intensity physical activity above 150 min/week was associated with reduced risk of prospective non-injurious and injurious falls in older women. Study Four:5 physical function limitation and frailty moderated the association between physical activity and injurious falls. Women with functional limitations or frailty had an increased risk of injurious falls with more activity, whereas women without functional limitations or frailty were less likely to fall if more physically active. Study Five:6 five patterns of physical activity participation over an 18-year follow-up period were identified: consistently low levels, consistently high levels, consistently some, decreasing and increasing physical activity. Women who reported consistently lower physical activity levels had the highest risk of falls. Studies Six and Seven:7 8 prospective associations between physical activity and falls; and between physical activity and physical function were bidirectional. Physical activity participation was associated with reduced risk of falls; however, women who had fallen had lower odds of undertaking physical activity 3 years later. Women who reported either no or some physical activity (ie, 1 to <150 min/week) had higher odds of developing physical function limitation. In contrast, women who undertook physical activity above the recommended level (ie, ≥300 min/week) had lower odds of developing physical function limitation. Women with reported physical function limitation had, on average, higher odds of undertaking no activity or some physical activity (ie, 1 to <150 min/week), but lower odds of undertaking physical activity above the recommended level.
What is the most important clinical impact/practical application?
These studies confirmed the need for widespread policy change and the provision of better services and programmes to enable physical activity participation. With an ageing population, a life-course approach is crucial in promoting physical activity from mid-life, targeting low activity levels and fall prevention to maintain physical function in older age. The associations between physical activity participation and injurious falls differed between women with or without physical function limitation and between women with or without frailty, highlighting the need for tailored physical activity promotion. System-level strategies and supportive policies are essential for integrating physical activity promotion into routine clinical and community services to contribute to healthy ageing.
Ethics statements
Patient consent for publication
Ethics approval
This study involves human participants and the ALSWH survey has ongoing ethical approval from the Human Research Ethics Committees (HRECs) of the Universities of Newcastle and Queensland (approval numbers H-076-0795 and 2004000224, respectively). Participants gave informed consent to participate in the study before taking part.
Acknowledgments
I would like to acknowledge the supervisory team Professor Cathie Sherrington (lead supervisor), Dr Saman Khalatbari-Soltani, Dr Xenia Dolja-Gore, Emeritus Professor Julie Byles, Dr Juliana Oliveira and Dr Marina Pinheiro for their invaluable guidance, support and expertise that have been instrumental in shaping the thesis and my research journey. I thank the team in the Australian Longitudinal Study on Women’s Health (ALSWH) for their data and all the study participants who provided the data.
Footnotes
X @venisa_kwok
Contributors WSK wrote the manuscript for the submission of BJSM PhD Academy Award and is responsible for the integrity of the work.
Funding The author receives Research Training Program Fees Offset and a scholarship from the Australian National Health and Medical Research Council (NHMRC) Centre of Research Excellence in the Prevention of Falls Injuries.
Competing interests None declared.
Provenance and peer review Not commissioned; internally peer reviewed.