Exercise as it relates to Disease/Relationship between physical activity and coronary heart disease in women

This Wikibook is an evidence-based analysis and critique of the research article:"Physical Activity and Coronary Heart Disease in Women" Lee I, Rexrode KM, Cook NR, Manson JE, Buring JE. 2001;285(11):1447–1454. doi:10.1001/jama.285.11.1447

What is the background to this research?

Coronary heart disease (CHD) is considered to be a type of heart disease which can be characterised by the narrowing of an individual’s arteries specifically the coronary arteries causing inability for the arteries to supply enough oxygen rich blood to the heart. Arteries which have become extremely narrow can lead to chest pain and shortness of breath during Physical activity (PA). If a coronary artery is completely blocked, it can result to a myocardial infarction (heart attack). CHD cause the highest amount of death in American women with statistics indicating an estimate of 18.2 million (7.2%) American adults living with CHD according to the Centres for Disease Control and Prevention (CDC) .  A survey conducted by National Health and Nutrition Examination Survey (NHANES) in 2020 concluded that 6.2% of women aged 20 and above have CHD, with even more recent data concluding modifiable risk factors for CHD including obesity, hypertension, diabetes, and sedentary behaviour are on a rapid incline .

The research paper to be critiqued by Dr Lee at el., studies the relationship between PA particularly walking (at light-moderate intensity based on pace), and CHD in women including those at high risk for developing CHD. The importance of studying this relationship between PA and CHD allows us to further understand the how beneficial PA is and the optimal type of PA (that yields the greatest benefits to lowering risks associated with CHD in women).

Where is the research from?

This publication was written by a team of 5 doctors all being in the Division of Preventive Medicine. Dr’s Lee, Manson and Burning specifically having done their PhD’s in the Department of Medicine Relating to women’s health. All authors have published numerous studies relating to women’s health and Cardiovascular disease with the authors having publish more the 80 research articles combined . All authors are well respected and highly reputable in terms of their educational backgrounds and as well as their fields of research relating to PA and its implications on health.

This research was conducted in the United States. American and Puerto Rican women were the subjects of the study however its implications are still relevant to women worldwide. This study was then published by Journal of the American Medical Association (JAMA) which is the most widely circulated medical journals in the world. JAMA has been ranked as one of the top leading journals in the discipline of medicine .

What kind of research was this?

This research was conducted in the form of a cohort (longitudinal) study due to all participants being followed over a period of 7 years. Subjects were selected from a Women's Health Study, which was a randomised double-blind, placebo-controlled trial where administration of low-dosage aspirin and vitamin E for primary prevention of cardiovascular disease, which Dr’s Lee, Cook and Burning took part in the research as well .

What did the research involve?

The research had a total of 39,372 participants who were healthy female health professionals aged 45 and over. These women were free of CHD. Participants were sent detailed questionnaires to complete that analysed their sociodemographic characteristics, health habits, and medical history. Follow up questionnaires were sent every 6 months participants to indicate their health behaviours as well as recent medical history. Baseline and follow up questionnaires asked women to estimate average time spent on exercise, pace of walking was also asked. Participants could choose from: no regular walks, walking 3.2 km/h (easy), 3.2-4.7 km/h (normal) and 4.8-6.3 km/h (brisk) and the number of flights of stairs climbed daily between 0 to ≥15. In a recent study results showed that the validity of a Self-Administered PA Questionnaire is reliable and valid as a measure of PA assessment .

Variables that could possibly influence the relationship between PA and CHD risk was accessed in the given questionnaires. Variables included age, weight, height, cigarette smoking status, diet (including alcohol consumption), history of hypertension, elevated cholesterol level, diabetes history, and family history of CHD.

What were the basic results?

Women that walked an average of 1 hour per week or and whose usual walking pace was at about 4.8 km/h had about a 50% decreased risk of developing CHD compared to women who did not walk regularly. Based on the questionnaire data women that engaged in high levels PA where less likely to engage in behaviour that increased CHD risk. Moreover, energy that’s expended during vigorous PA least 6 METs was examined. The results showed that when the highest and lowest categories of women were compared, there was a lower risk of CHD among the most active women that was of borderline significance (RR, 0.63; 95% CI, 0.38-1.04).

The study also examined whether there were any differences in the relationship between physical activity and CHD risk in women without and with CHD risk factors. There were no findings which led there to be an inverse association between women of normal weight and overweight women (P for interaction = .95). Also, there was no evidence regarding the inverse relationship differing between women without and with elevated cholesterol level (P for interaction = .71).

What conclusions can we take from this research?

Coronary heart disease leading cause of death for women world worldwide hence why it is important to study the relationship between PA and CHD. The data from the study was highly valuable and indicated the great benefits that PA has in lowering coronary heart disease in women. Results indicated that light to moderate activity predicted to lower risk. These finding are also congruent with a meta-analysis by Berlin et at., which concluded physically active individuals reduced risk of CHD by 50% compared those who were sedentary . Although the study being critiqued was conducted in the late 90s and early 2000s the results are still relevant. More research needs to be done as the optimal type, intensity and the duration of PA associated with lowering risk isn’t clear therefore, more research on the topic is crucial.

Practical advice

With the study been conducted in the late 90’s and early 2000’s and its findings still being relevant and give an important insight that demonstrates the positive effect that PA on CHD in women.

Women 45 or older including those at high risk of developing CHD can decrease their risk by:

• Engaging in light to moderate PA up to 1 hour per week regardless of pace which the study has shown to lower risk compared to those who don’t participate in any form of PA. Moreover, the study showed encouraging results as vigorous activities were not necessary for lower CHD rates.

• It is important that when exercising to increase intensity and minutes of exercise in the week overtime as this lowers risk of CHD more significantly and up to 2 times when comparing those who aren’t active

Further information/resources

Further information regarding the relationship between Coronary heart disease and physical activity have been listed below:

https://jamanetwork.com/journals/jama/fullarticle/195439#:~:text=Multiple%20epidemiologic%20studies%20have%20shown,those%20performing%20high%2Dintensity%20exercise.&text=However%2C%20the%20optimal%20level%20of%20exercise%20for%20preventing%20CHD%20is%20unclear.

https://academic.oup.com/aje/article-abstract/132/4/612/102184?login=false

https://www.ahajournals.org/doi/full/10.1161/JAHA.117.007725