Exercise as it relates to Disease/Which is more effective in reducing type 2 diabetes in women; walking or vigorous-intensity activity?

This is a critique of the journal article "Walking compared with vigorous-intensity Physical Activity and Risk of Type 2 Diabetes in Women" by Frank B. Hu, MD, PhD; Ronald J. Sigal, MD; Janet W. Rich-Edwards, ScD; et al. Published in 1999 in the JAMA Medical Journal.Hu F, Sigal R, Rich-Edwards J, Colditz G, Solomon C, Willett W et al. Walking Compared With Vigorous Physical Activity and Risk of Type 2 Diabetes in Women. Journal of Cardiopulmonary Rehabilitation [Internet]. 2000;20(2):130-131. What is the background to this research? Type 2 diabetes makes up over 85% of all diabetes cases and is the fastest growing chronic condition in Australia, for this reason, it is an important disease to prevent.Manson JE, Rimm EB, Stampfer MJ, et al. A prospective study of physical activity and the incidence of non-insulin-dependent diabetes mellitus in women. Lancet 1991 ;338 : 774–8Jeon C, Lokken R, Hu F, van Dam R. Physical Activity of Moderate Intensity and Risk of Type 2 Diabetes: A systematic review. Diabetes Care. 2007;30(3):744-752.Diabetes Australia [Internet]. Diabetesaustralia.com.au. 2020. Available from: https://www.diabetesaustralia.com.au/about-diabetes Type 2 diabetes is a progressive condition due to a genetic disposition where the body becomes resistant to the normal effects of insulin and/or gradually loses the capacity to produce enough insulin in the pancreas.Type 2 diabetes [Internet]. Diabetesaustralia.com.au. 2020 Available from: https://www.diabetesaustralia.com.au/type-2-diabetesAmerican Diabetes Association. 2009Diagnosis and classification of diabetes mellitus. Diabetes Care. 2009;32 Suppl 1(Suppl 1): S62-S67. Physical activity in the absence of weight loss improves blood glucose control and can prevent or delay type 2 diabetes, along with positively affecting the quality of life.Colberg S, Sigal R, Fernhall B, Regensteiner J, Blissmer B, Rubin R et al. Exercise and Type 2 Diabetes: The American College of Sports Medicine and the American Diabetes Association: joint position statement. Diabetes Care. 2010;33(12):e147-e167 The prevalence of diabetes is increasing year on year and in 2014 the World Health Organisation (WHO) recorded an increase from 108 million in 1980 to 422 million.Diabetes [Internet]. Who.int. 2020. Available from: https://www.who.int/news-room/fact-sheets/detail/diabetesDiabetes mellitus, fasting blood glucose concentration, and risk of vascular disease: a collaborative meta-analysis of 102 prospective studies. The Lancet. 2010;375(9733):2215-2222 Strong evidence has emerged which identifies the association between physical activity and reduced risk of diabetes. Moderate-intensity physical activity such as walking is the most prevalent physical activity among older adults and is feasible, accessible, and readily adopted method for reducing type 2 diabetes.Crespo C. Leisure-time physical activity among US adults. Results from the Third National Health and Nutrition Examination Survey. Archives of Internal Medicine. 1996;156(1):93-98Yusuf H. Leisure-time physical activity among older adults. United States, 1990. Archives of Internal Medicine. 1996;156(12):1321-1326 Observational studies have focused on the association of vigorous exercise and its effect on reducing the risk of type 2 diabetes. However, there is little research showing the comparison between the difference in the level of intensity of exercise has on reducing type 2 diabetes. Where is the research from? The research was published in JAMA which is an international peer-reviewed general medical journal that has been widely circulated around the world since 1883.[About | JAMA | JAMA Network [Internet]. Jamanetwork.com. 2020. Available from: https://jamanetwork.com/journals/jama/pages/about The subjects for the research were registered female nurses from the Nurses’ Health Study Cohort. The Nurses’ Health Study is one of the largest prospective investigations into women’s health and factors leading to chronic diseases.About NHS | Nurses' Health Study [Internet]. Nurseshealthstudy.org. 2020. Available from: https://www.nurseshealthstudy.org/about-nhs Established in 1976 when 121 700 US female registered nurses aged 30–55 responded to a mailed questionnaire. The questionnaire investigated their medical history, health practices, dietary intakes and the results from the studies play an instrumental role in shaping public health recommendations. Dr Frank B. Hu is the main author of the article and a professor of Medicine at the Harvard Medical School. His research focuses on diet, lifestyle, metabolic, and genetic determinants of obesity, type 2 diabetes, and cardiovascular disease (CVD).Frank B. Hu, MD, PhD - DF/HCC [Internet]. Dfhcc.harvard.edu. 2020. Available from: https://www.dfhcc.harvard.edu/insider/member-detail/member/frank-b-hu-md-phd/Frank B. Hu, , MPH, Ph.D. - Department of Medicine [Internet]. Researchfaculty.brighamandwomens.org. 2020. Available from: https://researchfaculty.brighamandwomens.org/BRIProfile.aspx?id=4603 Dr Ron Sigal is an Associate Professor of Medicine, Kinesiology, Cardiac Sciences and Community Health Sciences at the University of Calgary.Ronald Sigal [Internet]. University of Calgary. Available from: https://www.ucalgary.ca/diabetes-clinical-trials/RonaldSigal His current research focuses on physical activity, obesity, diabetes and CVD. All authors have a history with the topics being researched and therefore the knowledge presented is highly respected. What kind of research was this? The research was a prospective cohort study with data around the physical activity of 70,102 women as part of Nurses’ Health Study. Participants were observed at baseline (1986) and then followed up in 1988 and 1992 through a mailed questionnaire, inquiring about whether they had been diagnosed with diabetes.Salmerón J, Hu F, Manson J, Stampfer M, Colditz G, Rimm E et al. Dietary fat intake and risk of type 2 diabetes in women. The American Journal of Clinical Nutrition. 2001;73(6):1019-1026. Prospective studies are the gold standard in epidemiological studies.Elsevier, Science Direct. Prospective Cohort Study. 2018 [online] Accessed online via URL: https://www.sciencedirect.com/topics/medicine-and-dentistry/prospective-cohort-study It involves assessing a cohort of participants with similar conditions from baseline to a future date whilst identifying and outcomes of interest (type 2 diabetes).Euser A, Zoccali C, Jager K, Dekker F. Cohort Studies: Prospective versus Retrospective. Nephron Clinical Practice. 2009;113(3):c214-c217.Boston University of Public Health. Prospective versus retrospective cohort studies.2016 [online]. Accessed online via URL: http://sphweb.bumc.bu.edu/otlt/MPH-Modules/EP/EP713_CohortStudies/EP713_CohortStudies2.html The chosen research design requires a long-term follow-up, this study identified a 98% follow-up rate which provides high-quality data and validity of results. A prospective cohort study seemed more appropriate than a retrospective cohort study, due to the benefit of being able to target for a specific outcome.Song J, Chung K. Observational Studies: Cohort and Case-Control Studies. Plastic and Reconstructive Surgery. 2010;126(6):2234-2242. The alternate method of observational studies would not have been suitable for the desired method as it involves the direct observation of individuals without forced intervention.Manson J, Stampfer M, Colditz G, Willett W, Rosner B, Hennekens C et al. Physical activity and incidence of non-insulin-dependent diabetes mellitus in women. The Lancet. 1991;338(8770):774-778. What did the research involve? Over an 8-year period from 1986 70,102 female nurses who were free from diabetes were identified through a mailed questionnaire to participate in the study. The participants completed a physical activity questionnaire involving questions such as average time spent doing physical activity and the intensity of the activity. The data was analysed, and their baseline physical activity levels and weekly energy expenditure was calculated.AINSWORTH B, HASKELL W, LEON A, JACOBS D, MONTOYE H, SALLIS J et al. Compendium of Physical Activities: classification of energy costs of human physical activities. Medicine & Science in Sports & Exercise. 1993;25(1):71-80. Their energy expenditure was measured in metabolic equivalent task-hours (MET-hours) in relation to the different intensities of physical activity or walking. The above-mentioned questionnaire was first obtained in 1986 and then repeated two years later and in 1992. To control for confounding variables, the study also collected information on personal characteristics and lifestyle habits (e.g. smoking). Strengths; Large cohort and follow-up time Comparable results with similar studies Gold Standard Study Design Limitations; Questionnaires - leads to misclassification and over-reporting of physical activity. Self-reporting bias can appear due to different perceptions of exercise intensities, making it not as effective as electronic devices. Standard classification for energy expenditure based on the activities not the individual, therefore results used are an estimate. Waviered due to the cohort size All participants are Nurses with similar socioeconomic status and therefore may reduce external validity of the study and mean the results may not be generalisable to the general population.Pawlik, T and Sosa, J. Success in academic surgery: clinical trials. Springer Science and Business Media. 2013 ‘National Diabetes Data Group’ criteria were used to diagnose subjects and therefore exclude them. If the new criteria had been used, then some women would have become ‘excluded’ and vice versa. What were the basic results? The research showed that there is a positive relationship between physical activity and reduced risk of type 2 diabetes in women. Within the 8 year follow up 1419 cases of type 2 diabetes were recorded corresponding to an incidence rate of 265 per 100 000 person-years. In summary, the below points outline the key results; Women who increased their activity level from 2.1-10.4 MET-hours in 1986 to >10.4 MET-hours in 1988 had a lower risk (RR = 0.71; 95% CI, 0.55-0.93) compared with those who were consistently sedentary. Walking and vigorous activity was associated with comparable risk reductions when the energy expenditures were similar. Identifying substantial reductions of approximately 0.43 for individuals in the highest energy expenditure quintiles The relative risk associated with a 5 MET-hours per week increase in energy expenditures were 0.95 (0.92-0.98) for vigorous activity and 0.92 (0.88-0.95) for walking. Walking pace was an independent predictor for risk of type 2 diabetes. Multivariate RR for ‘normal pace’ was 0.72 compared to ‘brisk’ pace which was 0.41. What conclusions can we take from this research? If nothing else this study identifies that any exercise is better than none. Evidence shows that a 30-minute walk each day will reduce your risk of diabetes meaning it doesn’t have to be high intensity to see results. However, both intensities are associated with reduced risk of type 2 diabetes, therefore, it is a personal preference.Laaksonen D, Lindstrom J, Lakka T, Eriksson J, Niskanen L, Wikstrom K et al. Physical Activity in the Prevention of Type 2 Diabetes: The Finnish Diabetes Prevention Study. Diabetes. 2004;54(1):158-165. The findings show that the amount of physical activity required to reduce the relative risk is reliant on total energy expenditure rather than what type of exercise is undertaken or for how long. When the energy expenditure of moderate and vigorous was equivalent within the study the benefits were comparable. Whilst there are many other inflammatory markers that can increase risk of type 2 diabetes, regular physical activity alone is shown to reduce this risk regardless of changes in weight loss, lifestyle habits (e.g. smoking) or other metabolic factors.Hu F, Meigs J, Li T, Rifai N, Manson J. Inflammatory Markers and Risk of Developing Type 2 Diabetes in Women. Diabetes. 2004;53(3):693-700. There are many misconceptions regarding the need to exercise vigorously to see any benefit however these results dismiss them. The findings support the current guidelines from 'Centers for Disease Control and Prevention'Pate R, Pratt M, Blair S. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA: The Journal of the American Medical Association. 1995;273(5):402-407. and the 'National Institutes of Health'Physical activity and cardiovascular health. NIH Consensus Development Panel on Physical Activity and Cardiovascular Health. JAMA: The Journal of the American Medical Association. 1996;276(3):241-246. that individuals should participate in at least 30 minutes of moderate physical activity at least five days a week. Practical Advice Implementing some form of physical activity into your daily routine will not only decrease your risk of type 2 diabetes it will also improve your daily life and overall health.Warburton D. Health benefits of physical activity: the evidence. Canadian Medical Association Journal. 2006;174(6):801-809. Start somewhere; often getting started is the hardest part! Use the Physical Activity Guidelines as recommendations. Make it enjoyable; find a form of physical activity that you enjoy (e.g. swimming, tennis, aerobics, walking) which will make it 'easier'. Avoid long periods of sedentary behaviour (i.e. watching TV, sitting at your desk) by breaking it up with physical activity. Choose activities that suit your lifestyle If any form of physical activity causes severe pain or you have concerns, seek expert advice Further Information If you are interested in further information please see the links below; Find out if you’re at risk of diabetes? https://www.diabetesaustralia.com.au/risk-calculator Physical Activity Fact Sheet. Get Active. https://www.heartfoundation.org.au/active-living/get-active Need help getting started? Find an exercise Professional nearby; https://www.essa.org.au/find-aep References