Exercise as it relates to Disease/Television viewing time and its association with cardiovascular disease mortality in adults

This fact sheet is an analysis of the journal article Television Viewing Time and 13-year Mortality in Adults with Cardiovascular Disease: Data from the Australian Diabetes, Obesity and Lifestyle Study (AusDiab), by u3102880

What is the background to this research?
Cardiovascular disease (CVD) is currently one of the most prevalent health conditions in Australia, accounting for 14.6% of deaths in 2011. Research has shown that physical activity plays a large part in reducing risks associated with CVD. However, evidence also exists which suggests that sedentary behaviour may increase the risk of some health conditions, independent of physical activity levels.

One form of sedentary behaviour which has been linked to poor health outcomes is that of television viewing. This activity occupies a large amount of leisure time for many Australian adults, with most typically viewing an average of 13 hours of TV per week. Poor health outcomes such as obesity, type 2 diabetes have been associated with excessive television viewing.

While there is a known relationship between sedentary behaviour and poorer health outcomes of CVD, little research has been done to look at the long term relationship between television viewing time and its relationship with CVD mortality in the long term. Using data from the AusDiab study, the selected paper looks at the relationship between CVD mortality and television viewing time over a 13-year period.

Where is the research from?
This study was carried out using data from the Australian Diabetes, Obesity and Lifestyle Study (AusDiab), using a sub-sample of participants who were excluded from the original study due to pre-existing self-reported CVD.

The AusDiab study was conducted with funding from the Federal Government of Australia through a National Health and Medical Research Council grant, and was coordinated by the Baker IDI Heart and Diabetes Institute.

What kind of research was this?
This study is a prospective cohort study, a type of epidemiological study which follows a large group of people over time, with data collected periodically. Cohort studies are useful for measuring exposure to risk factors against incidence of disease over a long period of time, and with a large number of participants.

What did the research involve?
Data collection for the original AusDiab study occurred in three rounds: baseline (1999–2000); phase 2 (2004-2005); and phase 3 (2011–2012). Samples were taken from 42 randomly selected areas from each state or territory and included both urban and non-urban locations. The current study included 609 participants (241 females, 368 males) who were not included in the original study based on a pre-existing history of coronary heart disease (CHD). Self-reported information was obtained on: Biomedical information was obtained by trained professionals and included: Mortality was determined by linking the cohort to the National Death Index (NDI) up to 9 January 2014, however as information on cause of death was not available prior to 30 November 2011, information on CVD specific mortality was not analysed in this study.
 * TV viewing time
 * Frequency, intensity and duration of physical activity
 * Dietary information
 * Demographic information such as age, sex, educational attainment, marital status, household income, place of residence and smoking status
 * Waist circumference
 * Height and weight
 * Resting blood pressures
 * Fasting and two-hour plasma glucose levels
 * Fasting serum triglycerides
 * Total cholesterol and HDL-C
 * Lipid medication use

What were the basic results?
A positive linear relationship was observed between 13-year all-cause mortality, that is, death from any cause, and amount of time spent watching TV, with those in the high viewing category (≥4 hours per day) having the highest rate of mortality, and those in the lowest viewing category (<2 hours per day) having the lowest rate of mortality. When compared to watching <2 hours of TV per day, watching ≥4 hours of TV per day was associated with a 52% increase in mortality.

Watching more TV was positively associated with being older, having a lower household income, higher systolic blood pressure, higher BMI and likelihood of having diabetes mellitus. The relationship between TV viewing time and mortality was independent of smoking, education, age, sex, hypertension, waist circumference, BMI and physical activity.

What conclusions can we take from this research?
The results show that adults with CVD who watch more than 4 hours of TV per day have a 52% higher mortality rate from any cause than those who watch less than 2 hours per day, regardless of factors such as age, sex, education, smoking, BMI or lipid levels. This relationship is linear, with those who watch more TV at the highest risk of mortality from any cause.

It is important to note that this study was not able to determine a causal relationship between TV viewing time and mortality in CVD patients. Factors such as whether TV viewing time itself was influenced by CVD status were also not measured, that is, whether those who may be at higher risk of mortality from CVD tend to watch more TV, rather than the other way around.

Limitations of the study include the use of self-reported data to measure sedentary behaviour, rather than technologies such as accelerometers which have been shown to be more reliable, as well as the use of self-report for measures of physical activity and dietary intakes. Other potential confounding variables may have been missed from the study, for example depression and mental health factors, which have been shown to be related to both TV viewing time and increased mortality.

Practical advice
While it is important to include recommendations for physical activity as part of treatment plans for CVD patients, this study highlights the need to include recommendations for limiting sedentary behaviour such as TV viewing as well. Those with CVD who are looking to reduce their risk may consider limiting TV viewing time as a strategy for reducing sedentary behaviour.

Further information/resources
Further information on sedentary behaviour can be found on the links below:
 * ASCM - Reducing sedentary behaviour: https://www.acsm.org/docs/brochures/reducing-sedentary-behaviors-sitting-less-and-moving-more.pdf
 * Australian Government Department of Health Physical Activity Guidelines: http://www.health.gov.au/internet/main/publishing.nsf/Content/health-pubhlth-strateg-phys-act-guidelines
 * Sedentary Behaviour Research Network: http://www.sedentarybehaviour.org/what-is-sedentary-behaviour/