Effects of High-Intensity Interval Training on Depressive Symptoms in Hong Kong Older Adults with Mild and Moderate Depression: A Cluster-Randomized Controlled Trial

Depression in later-life is a common health problem in aging societies (WHO, 2020). It is associated with poor quality of life, increased risks of morbidity (e.g., physical impairment, cognitive decline) and mortality (e.g., suicide) (Wei et al., 2019). People with severe depression may develop serious psychotic symptoms (e.g., delusions) and have higher mortality and disability than those with mild and moderate depression (NCD Watch, 2012). Effective treatment for mild and moderate depressive symptoms can considerably prevent the deterioration of depression with severe and psychotic symptoms (Hall & Reynolds-Iii, 2014) and this is particularly important for older adults.

Traditional moderate-intensity continuous training (MICT) (e.g., Baduanjin Qigong) has proved to be effective in preventing and alleviating depressive symptoms among older adults (Liu et al., 2012; Zou et al., 2018). However, older adults with mental illnesses have poorer engagement and compliance with MICT programs (Martland et al., 2020). In recent years, as a novel type of exercise, high-intensity interval training (HIIT), which includes repeated bouts of high-intensity effort followed by varied recovery times, appears to be a promising approach for overcoming limitations in traditional MICT programs (Korman et al., 2020; Martland et al., 2021). HIIT shows similar or greater effects on physical fitness and mental health among older adults than MICT, with more time-efficiency, few safety concerns, more enjoyment and higher compliance (Keating et al., 2020).

Considering there is little evidence of HIIT benefits related to the older adults with depression, the current study aims to evaluate the effectiveness of a 16-week HIIT intervention on depressive symptoms and other health-related outcomes among Hong Kong Chinese older adults. 144 community-dwelling older adults with mild and moderate depression from nine elderly centres (i.e., clusters) will be recruited and randomly assigned into one of three groups by cluster randomization, including a HIIT group, a MICT control group (Baduanjin Qigong), and a non-exercise control group (recreation workshops). The primary outcome will be objectively measured depressive symptoms using salivary cortisol. Secondary outcomes will include self-reported depressive symptoms, physical fitness, sleep quality and quality of life. All outcome variables will be measured at pre-intervention, post-intervention, and 3 months following intervention completion, respectively. It is expected that older adults in the HIIT group will gain more improvement in depressive symptoms and other health-related outcomes compared to the control groups. The research findings may have considerable impacts on future prevention and treatment of mental disorders and may also contribute to promoting healthy ageing among Hong Kong older adults.