Developing physical Activity and Sedentary behaviour thresholds for the Secondary prevention of Heart disease 鈥� the DASSH trial

In people with heart disease, physical inactivity is a major risk factor for further heart disease and death. Currently, there are no physical activity guidelines specifically for people with heart disease, and it is not known whether the public health physical activity guidelines apply to this population.

Repeat heart attacks are common and costly for individuals, families and the healthcare system. It is therefore crucial that disease-specific physical activity guidelines are developed to guide clinical practice.

Associate Professor Nicole Freene and her research team from the Health Research Institute, the University of Sydney and Linkoping University (Sweden) aim to investigate the relationship between physical activity, sedentary behaviour and heart disease using two studies to guide future heart disease research, policy and practice.

In Study 1 (DASSH cut-point)

164 people with coronary heart disease will complete a treadmill test and activities-of-daily-living with simultaneous measurement of oxygen-uptake and device measured (accelerometer) physical activity.

This will improve the accuracy of device-measured physical activity by developing heart disease specific accelerometer cut-point equations for different physical activity intensities based on the relationship between oxygen uptake and accelerometer activity counts from these activities.

A limitation of the few studies that measure physical activity using accelerometers in this population, is the use of inappropriate accelerometer intensity cut-points derived from healthy populations. Without accurate measurement of physical activity, clinicians are unable to monitor physical activity adherence, nor the effectiveness of physical activity interventions. Additionally, researchers are unable to determine the relationship between physical activity and health outcomes to develop disease-specific physical activity guidelines which may differ from the public health guidelines.

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In Study 2 (DASSH)

Using linked data from the 45 and Up Study (a large-scale prospective cohort study of women and men 45 years or older from the general population of NSW), we will develop thresholds for sitting time and physical activity above or below which health is impaired in 50,000 people with heart disease.

The independent relationship between self-reported moderate-to-vigorous physical activity (min/day) or self-reported sedentary behaviour (hr/day) and recurrent cardiac events and death will be explored. These thresholds will be validated in a sub-sample of participants and compared to the public health physical activity guidelines which are routinely recommended.

Ultimately, this trial will guide disease-specific physical activity guidelines and interventions, helping more people with heart disease live longer and healthier after a cardiac event.