Exercise as it relates to Disease/The effects of Physical Activity on Sitting: The Silent Killer of Sedentary Adults

In 1975, the ‘Life. Be In It’ advertising campaign was launched on Australian television and radio to encourage us to be more active each day by simply by moving for 30 minutes each day. The message was delivered by a cartoon character called ‘Norm’ – a typical Aussie bloke, complete with a bulging beer gut. The aim of the campaign was simple: to encourage all Australians to become more active to prevent chronic disease.

In today’s technology-fuelled world, we are stilled reminded to take a break from our sedentary lifestyle (eg prolonged sitting watching television or working at a computer), whether by the ‘micro-pause’ applications installed on corporate computers or by gentle vibrating reminders to ‘move’ on our wearable activity monitors. While people are heeding the message and increasing their level of physical fitness, is there still a need to push the message to ‘move’? The answer is YES according to researchers who have recently completed a study into the strength of the relationship between sedentary time, the risks associated with a number of serious health issues and physical activity.

What is the background to this research?
While regular physical activity has been established as a preventative measure to the risk of obesity, heart disease and other health issues, studies have shown that the increasing trend towards a more sedentary lifestyle, due to shifting work habits (office-based vs outdoor manual jobs) and more leisure time, is countering the positive effects of physical activity. The researchers set out to determine the magnitude, consistency and manner of correlation between the time people spend on sedentary activities and serious health outcomes regardless or independent of the person’s level of physical activity. In other words, are people still at risk of serious health issues if they achieve the recommended amount of physical activity but still spend a large amount of time on sedentary activities?

Where is the research from?
The research was conducted by members drawn from the Institute of Health Policy, Management and Evaluation, and the Faculty of Kinesiology and Physical Education, University of Toronto; University Health Network-Toronto Rehabilitation Institute, Cardiovascular Prevention and Rehabilitation Program; Sunnybrook Health Sciences Centre; York University; and Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada. Individual members are supported financially from a variety of professional bodies; however, this study was not explicitly funded. The study was published in the Annals of Internal Medicine, and online facility maintained by the American College of Physicians (ACP). Authorised subscribers to the ACP website can download the study as a pdf.

What kind of research was this?
The researchers undertook this study as a ‘meta-analysis’¬¬ following contemporary and approved review guidelines. A key benefit of this approach is the aggregation of information often makes it easier to determine a trend than from an individual study.

What did the research involve?
Data was extracted from a number of medical databases using searches restricted to English-language primary research articles through August 2014. Hand searches were also conducted to supplement the electronic searches. Agreed keywords – inactivity, exercise, morbidity etc – were used for formulate the meta-analysis search criteria: (exercise OR physical activity OR habitual physical activity) AND (sendent* OR inactivity OR television OR sitting) AND (survival OR morbidity OR mortality OR disease OR hospital* OR utilization). Two reviewers independently scored data extracted from articles that satisfied the search criteria for quality, with inconsistencies discussed with a third reviewer.

What were the basic results?
41 out of 20,980 articles met the researchers’ eligibility criteria. The selected studies covered almost 830,000 participants. The researchers found that greater sedentary time was positively associated with an increased mortality risk for all-cause, heart disease, cancer, and type 2 diabetes. Moreover, the adverse health risks associated with sedentary time generally decreased in participants who engaged in higher levels of physical activity. In one study in Australia, male and female participants over the age of 45 who reported less than 8 hours of sitting per day had a 14% lower risk for potentially preventable hospitalisation.

How did the researchers interpret the results?
The researchers concluded the association between sedentary time and the risk of adverse health outcomes may vary with the level of physical activity and becomes less pronounced as the level of physical activity increases.

What conclusions should be taken away from this research?
Prolonged sedentary time was independently linked with the risk of adverse health outcomes regardless of physical activity.

What are the implications of this research?
To date, the focus of health campaigns has been on encouraging people to participate in physical activities. This research suggests there should also be an increased public awareness of the benefits of reducing sedentary time each day – remember to ‘move’. The researchers advocate for further research into the effectiveness of interventions to target sedentary time independently from, and in addition to, physical activity.