Exercise as it relates to Disease/How does physical activity interact with coronary artery disease?

Background research
Coronary artery disease (CAD) is a common condition that primarily affects the cardiovascular system, in particular the major blood vessels (coronary arteries) that supply the heart with blood, oxygen, and nutrients. CAD is the leading single cause of disease burden and death in Australia, in 2020-21 an estimated 571,000 Australians over the age of 18 reported having CAD, this resulted in 16,600 deaths nationwide in 2020, making up for 10% of Australian deaths that year. There are many risk factors that can increase someone's chances of developing CAD, some of the main ones are: age, sex, family history, smoking, drinking, and physical activity.

Physical activity has been known to have significant positive effects on many diseases, particularly ones that affect the cardiovascular system, This means that a disease like CAD is strongly influenced by physical activity levels. A study conducted in 2017 placed patients suffering from CAD into 3 different intervention groups based on their lifestyle-related risk factors such as physical inactivity, BMI, and smoking habits. This study's results showed that implementing changes to someone's lifestyle that target their lifestyle-related risk factors does positively impact CAD.

These results from this study appear to align with other available research however the process and reliability of it will be critiqued throughout this page.

Where is the research from?
The article referred to was published in 2017 by the Journal of the American College of Cardiology, they are known for their original peer-reviewed clinical and experimental reports on all aspects of cardiovascular disease. (5) The Journals impact factor is ranked 5th out of 143 in Cardiac & Cardiovascular Systems and is available in 11 international databases.

The complete data found in this study comes from 711 participants that were spread across 15 hospitals in the Netherlands.

What kind of research was this?
The article states that its research is that of a randomised controlled trial, however there is evidence of some randomised controlled trial and multi-centre characteristics being used to create the 3 different intervention groups and gather data from multiple hospitals.

What did the research involve?
The research for this study involved a large amount of cooperation from many patients with CAD and nurses throughout multiple hospitals. There were 562 male participants and 149 female participants, requirements for these participants included hospitalisation for acute coronary syndrome, and/or coronary revascularization within the last 8 weeks and having 1 or more lifestyle-related risk factor. Although all participants had CAD these lifestyle-related risk factors varied between participants (low physical activity, high BMI, smoking habit) and altered what their intervention would be. Below are the 3 interventions they were given.

Intervention group with low physical activity levels:

Philips DirectLife offers an Internet-based program aimed at improving physical activity. An accelerometer measures physical activity and an online coach provides personalized feedback. Access to this program was for the duration of 1 year.

Intervention group with high BMI:

Weight Watchers offers a program that emphasises a healthy diet, changing unhealthy behaviour and regular physical activity, and uses group motivation, coordinated by a Weight Watchers coach. Access to this program was for the duration of 1 year.

Intervention group with smoking habit:

Luchtsignaal is a smoking cessation program in the Netherlands that uses telephone counselling based on motivational interviewing by trained professionals, for the duration of 3 months. Nicotine replacement or varenicline therapy was prescribed, as appropriate.

The participant's baseline data was collected after discharge from hospital so they can be compared with their results 12 months later. The data that was collected included cardiovascular risk factors, cardiovascular history, physical activity, smoking status, medication use, blood pressure, body weight, height, waist circumference, BMI, body composition, fasting blood samples, and a 6-minute walking distance test.

There's an extremely large amount of data that's been gathered for this study. It's clear that if this were been done on a specific population or only use one intervention group there would be less variation in data and that could lead to finer results and possibly achieve a better dropout rate than 11.3%. With that being said the Authors have done well to convey this complex investigation they are doing. A concern that is apparent in the method is that people's physical activity levels and smoking habits are self-reported. This can create a level of unreliability amongst the data.

What were the basic results?
The results that are relevant in the case of this page will be those that came from the physical activity intervention and control groups. At baseline, 63% of participants did not meet the target for adequate physical activity, making this the 2nd most prevalent lifestyle-related risk factor behind a high BMI and would suggest a relationship between physical activity and CAD.

The 6-minute walking test was the main test used to show an improvement in physical activity, the results are:

- 45% of physically inactive participants in the intervention group saw a change in their 6-minute walking distance test that was greater than or equal to a 10% improvement

- 40% of physically inactive participants in the control group saw a change in their 6-minute walking distance test that was greater than or equal to a 10% improvement

What conclusions can we take from this research?
From the research, we can conclude that physical activity does positively interact with CAD. The extent of its effects don't seem to be fully investigated in this research but the evidence is still there. The results of the control group are somewhat close to the results of the intervention group (only a 5% variation), this brings up a few questions such as was self-reporting physical activity levels a poor choice from the researchers or was the internet-based program provided the best option for increasing physical activity levels. Because of these questions, it would be wise to investigate further into this topic after some reflection on some possible mistakes that were made here.

Practical advice
These results may suggest that physical activity benefits CAD on a smaller scale than what was expected but its important to consider that the participant's baseline statistics were taken shortly after they were discharged from hospital, this means the results in the control group could just be them naturally recovering from their hospitalisation. If this study were to be replicated there should be a larger window between taking the hospitalisation and the recording of baseline statistics. Although there may be flaws in this research the information it offers is still valuable and holds a large amount of credibility.

Further information/resources
Heart foundation Australia -