By 2030, the number of people globally aged over 60 years will surpass the number of children aged under ten (UN, 2017). Older adults are the least active section of the population and typically spend 60%-80% of their waking hours, sedentary (Harvey et al., 2015). They are also the section at most risk of mobility disability and functional impairment. The protective effect of physical activity on health may be reduced with prolonged bouts of sedentary behaviour, which is also an important determinant of physical function, frailty and falls in older adults (Landi et al., 2010; Peeters et al., 2010). The aim of this thesis was to investigate the relationship between physical activity, sedentary behaviour and physical impairment, and to develop a pilot intervention to reduce sedentary time in a group of community dwelling older adults.
A cross-sectional study examined whether sedentary behaviour or physical activity had the strongest association with physical impairment among community dwelling older adults. A systematic review of SB interventions was then done to determine which intervention mechanisms were likely to be successful with this cohort. The review informed the design and subsequent delivery of an education based, group supported sedentary behaviour
reduction intervention that was practical, easy to administer and tolerable to a broad range of participants.
Findings from the cross-sectional study suggested that the tests of physical function were more strongly associated with physical activity than with sedentary behaviour. However, when total sitting/ lying time was included in the analysis, there was little difference in the association. Participants were found to be sedentary approximately 60% of the waking day (9.5 hrs.day-1) and to sit/lie/sleep a total of 18.3 hrs.day-1. However total steps were recorded at 9745.day-1 and total MVPA at 168.7 min.week-1, indicating a highly active cohort of participants. The systematic review demonstrated that the methodological quality of sedentary behaviour interventions was generally low and heterogeneity in study design was high. Although successful interventions used a broad range of behaviour change techniques to modify behaviour, evidence suggested that contextualising sedentary behaviour and targeting specific behaviours were also key ingredients. Findings from the intervention
showed no statistical significance between groups over time for SB reduction. A small increase in total steps pre- to post-intervention of 3.5% was accompanied by a reduction in total objectively measured sedentary behaviour of 4.1%, suggesting that the behaviour may have been displaced by additional stepping activities. Total steps/day-1 among the intervention group were 8431, indicating a high functioning group and limited opportunity for increased activity as a result of the intervention. Future sedentary behaviour interventions should include behaviour change functions that seek to raise awareness, educate and provide social or peer support for older adults. They should also target time spent in non-purposeful sedentary behaviours that are often conducted at home and when alone.
Older adults, particularly those for whom increased physical activity is difficult, may benefit from education-based, behaviour change interventions that seek to reduce time spent in prolonged sitting or lying postures. The ideal, or optimum, dose of sedentary behaviour reduction needed for positive clinical outcomes is still unknown but the findings suggest that even 1 hr.day-1 of sedentary time substituted for LIPA is associated with better physical function among older adults. The findings also suggest that low burden interventions conducted where participants can avail of social support, may lead to higher levels of participant retention. SB research among older adults is still in its infancy and more research is needed to establish whether a dose-response relationship exists between SB and geriatric syndromes across the functional spectrum.
In summary the contributions of this thesis to the field of sedentary behaviour research are:
i. Total PA may be a more useful indicator of physical functional status for older adults than any subdivision of PA. Researchers should be careful to match the sensitivity and range of assessments undertaken to the expected physical functional ability of participants.
ii. Sitting/lying/sleeping may have a broader influence on physical functional status than SB alone. Due to the unique behavioural patterns demonstrated by older adults, research with this cohort should incorporate sit/lie/sleep measures in addition to SB measures where physical function is to be determined.
iii. Behaviour change strategies are an important ingredient in the development of SB reduction/ displacement interventions for older adults. Future investigations should use structured approaches (like the BCW) to design interventions that focus on displacing non-purposeful sedentary time. Ideally, intervention designs should incorporate low-burden BCTs that educate older adults and use the influence of peers and group support to encourage self-efficacy and retention among participants.
|Date of Award||Jun 2021|
|Supervisor||Chris Bleakley (Supervisor), Marie Murphy (Supervisor) & Jacqueline Mair (Supervisor)|
- Physical activity