Exercise as it relates to Disease/How physical activity affect mortality in patients with cardiovascular disease

This wikipage is an assignment for the University of Canberra (subject: Health, Disease and Exercise / 2021). It is a critical assessment of the article "Mortality reduction with physical activity in patients with and without cardiovascular disease" by Jeong SW et al. (2019)

What is the background to this research?
Cardiovascular Disease (CVD) has become the top cause of morbidity and mortality worldwide. Evidence suggests that patients with CVD are less prone to participate in physical activity and more likely to have a sedentary lifestyle. From this however it is not possible to conclude that patients with CVD could decrease their rate of mortality by engaging in physical activity. To date, no studies have analysed the benefit of physical activity in primary or secondary CVD.

This study aims to evaluate the incidence of physical activity in patients with CVD to identify the relationship between mortality, physical activity and CVD

Where is the research from?
This study used the National Health Insurance Service-Health Screening Cohort (NHIS-HEALS) which is a population-based cohort created in Korea in 2015 in order to provide researchers with useful data regarding non-communicable diseases and health risk factors.

All authors of this study were involved with the Department of Internal Medicine at the Cardiovascular Centre in Seoul, Korea.

This research was funded by the Basic Science Research Programme through the National Research Foundation of Korea. No conflict of interest was declared.

What kind of research was this?
The design of this study was a Retrospective Cohort Study (RCS). The participants who underwent a screening program and completed surveys on physical activity between 2009 and 2015 were extracted from the cohort.

RCS' are usually advantageous due to having the potential to access the complete individuals profile and their exposure to a specific condition, including a thorough follow up of the individual’s condition.

They also have the potential to establish a correlation between physical activity and CVD levels. However, in comparison with a Randomized Control Trial, it may be less effective in establishing a cause and effect due to the existence of different factors that may alter the participants’ condition.

What did the research involve?
This RCS consisted of 441,798 profiles of individuals with and without CVD. These profiles were taken into consideration to analyse the participants’ physical activity and CVD levels.

These profiles belonged to individuals made up part of the Cohort from at least 2002 and who completed surveys regarding their physical activity between 2009 to 2015. The selected individuals were split into two different groups: Primary prevention group (individuals without CVD) and secondary prevention group (individuals with) CVD.

By being part of the NHIS-HEALS the individuals had the duty of filling out a series of self-report standardized questionnaires (a 7-day recall method was used to collect data regarding physical activity), participating in anthropometric and blood pressure measurements and laboratory tests using blood and urine samples.

There were two different outcomes. The primary one measured all-cause mortality where vital status, date of death and causes of death were certified. The secondary outcomes were cardiovascular or non-cardiovascular death.

One of the major limitations of this research is the Recall Bias in the data collection. All physical activity data relies on the self-report questionnaires administered by the Cohort guidelines. Not only individuals may under or over-report physical activity, but also, only leisure time physical activity was contemplated in the study. Other physical activity such as home or occupational duties may influence the results.

Another important limitation of this study is that only aerobic physical activity was evaluated when calculating the levels of physical activity. Therefore, data regarding musculoskeletal physical activity (AKA Strength training) was not evaluated leaving no option to the researcher but to make assumptions regarding levels of physical activity.

What were the basic results?
Out of the 441,798 participants 131,558 (29.8%) were found to have CVD while 310,240 (70.2%) had no history of CVD.

In the matter of physical activity, it was found that those participants with CVD were less physically active than those without CVD (measured in MET-min/week. Range 0-2429 MET-min/week). Also, 27.2% of the Secondary prevention group was found to be totally sedentary while only 24.4% of the primary prevention group was. The difference between prevention groups in these two findings was statistically significant (P<0.001).

Regarding rate of mortality, and after a follow up of 10 years (5.9 median), it was found that those with CVD had a significantly increased risk of mortality (Hazard Ratio 2.57).

When analysing both physical activity and rate of mortality, it was possible to observe that they have an inverse relationship. An increase in 500 MET-min/week showed a 14% risk reduction in mortality for the secondary prevention group whilst it was only 7% for the primary prevention group.

What conclusions can we take from this research?
Based on the findings, it is possible to conclude that individuals with CVD may be greatly benefited by participating in physical activity (>500 MET-min/week) by decreasing the rate of mortality. As well, even though patients without history of CVD have a lower rate of mortality than those with CVD, they can also see a benefit from participating in physical activity. This opens up another discussion regarding prevention of CVD when participating in physical activity.

Practical advice
Even though it is clear in this research that physical activity may reduce the risk of mortality in patients with CVD and to an extent in patients without, it is important to note that different types of physical activity have different adaptations and physiological effects. These adaptations may also differ from individual to individual due to other factors linked to lifestyles, genetics and other conditions. Therefore, any individual, regardless of their cardiovascular status, must consult with a health professional before participating in any physical activity.

Further information/resources
World Health Organization / Cardiovascular Diseases

Subjects with cardiovascular disease or high disease risk are more sedentary and less active than their healthy peers

Physical Inactivity and Cardiovascular Disease

Cardiovascular Effects and Benefits of Exercise