Exercise as it relates to Disease/Diabetes and the benefits of physical activity

Paper: Kriska, A.M., Edelstein, S.L., Hamman, R.F., Otto, A., Bray, G.A., Mayer-Davis, E.J., Wing, R.R., Horton, E.S., Haffner, S.M., and Regensteiner, J.G. (2006) Physical Activity in Individuals at Risk for Diabetes: Diabetes Prevention Program Med Sci Sports Exercise 38(5): 826-832

What is the background to this research?
Diabetes is worldwide health concern and is currently identified as the world’s fastest growing chronic health condition. In 2015, it was estimated that 1 in 11 adults had diabetes (over 415 million people), 12% of global health expenditure was diabetes related, and every 6s a person dies from diabetes. In Australia alone, approximately 120,000 per year are diagnosed with diabetes, the estimated annual cost impact is $14.6 million, with diabetes the biggest challenge to the health system. Health related complications associated with diabetes include blindness, amputation, heart disease, and kidney disease.

Where is the research from?
The research was conducted by Diabetes Prevention Program (DPP) Research Group, of the George Washington University. The DPP is funded by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and set up to conduct clinical trials on issues relating to diabetes and diabetic populations.

What kind of research was this?
This research was conducted as a randomised clinical trial of diabetes prevention, with data collected from 27 centres across the United States of America (USA) over a 4-year period. Focusing on interventions with the potential to delay the onset of diabetes, a total of 3234 overweight individuals ≥ 25 years old (mean age 50.6 ± 10.7 years) of diverse ethnicity (45% from ethnic or racial groups) with elevated fasting glucose levels and IGT were recruited to participate. Other inclusion criteria included body mass index value ≥ 24 kg.m-2, ability to walk ¼ mile in 10 min, and fasted plasma glucose concentration of 95-125 mg.dL-1 and 140-199 mg.dL-1 post a 75g oral glucose tolerance test (OGTT).

The DPP research concentrated on a diet and exercise lifestyle intervention or treatment with metformin, a drug that works to help restore the body’s response to insulin by decreasing the amount of blood sugar the liver produces and that the intestines or stomach absorb, with participants randomly assigned to receive different treatments.

What did the research involve?
The purpose of this study was to examine: 1) physical activity and measures of obesity and glucose intolerance via three different physical activity questionnaires, 2) activity levels of a cohort of participants at risk of developing diabetes against a broader sample of participants with impaired glucose tolerance (IGT).

The study evaluated baseline, self-reported levels of leisure activity using three physical activity questionnaires. The three questionnaires used to quantify the amount of leisure physical activity/exercise, incorporated reporting periods of 7 days to 1 year.

- Low-Level Physical Activity Recall (LOPAR; past 7 d) - modified version of a 7-day physical activity recall validated for use in population with low levels of regular physical activity. Included assessment of all forms of physical activity, including occupational, leisure and home, with leisure activity being the focus. Total energy expenditure was quantified in terms metabolic equivalents (METs) and the of number of hours spent completing very light (1.0-1.5 METs), light (2-3 METs), moderate (3-5 METs) and heavy (≥ 6 METs) activities.

- Third National Health and Nutrition Examination Survey (NHANES III; past month) - questionnaire that asked if participants had engaged in specific activities (ie. walking, jogging, bike riding, swimming, aerobics, dancing, calisthenics, gardening, weightlifting) or other exercise, sports or physically active hobbies. Leisure activity was quantified as times per month with duration or intensity data not collected.

- Modifiable Activity Questionnaire (MAQ; past year) - occupational and leisure activities with leisure activity the main focus of this study. Questionnaire included a comprehensive list of leisure activities developed from pilot work and shown to be reliable and valid through evaluations with activity monitors, field-based fitness testing, and assessments of energy expenditure (doubly labelled water method). Participants reported leisure activities undertaken as well as an estimate of frequency and duration. Relative intensity for each activity was calculated in terms of METs and reported as MET-hours per week. Energy expenditure at rest was represented as 1 MET, and 10 METs equated to ten times resting energy expenditure.

What were the basic results?
Significant correlations were reported for leisure activity data across all three surveys, although stronger relationships were found between MAQ and NHANES III when compared to the LOPAR.

Results from this study were generally consistent with previous literature. Results are best explained under key variables:

Gender / Age / Ethnicity - across all three surveys, men more physically active than women; older participants more active than younger ages, with most active group ≥ 60 years; physical activity varied by ethnicity; women and men less active in the DPP cohort compared to NHANES III for most ages and ethnicities; however, when matched for impaired glucose tolerance the DPP cohort were more active than participants NHANES III subgroup.

BMI / Waist: Hip Ratio / Blood Glucose - inconsistent results for association between physical activity and fasting or post load glucose values; physical activity estimates from MAQ and NHANES III significantly and inversely associated with BMI, waist: hip ratio, fasting and 75g OGTT insulin measures, fasting plasma proinsulin and amount of glucose attached to haemoglobin (HbA1c) for men and women; LOPAR was significantly and inversely correlated with fasting and 30 min post insulin in men only; DPP women and men less active compared to NHANES III for BMI.

Influence of Time - physical activity reported via MAQ and LOPAR questionnaires was not strongly related. Whilst shorter surveys are thought to be less influenced by recall bias, assessments over a longer period are believed to better reflect typical behaviours and be less influenced by changes in health, time pressures and weather. Previous studies have found that the average of four weekly recalls showed a stronger relationship with past year activity comparted to a one-off recall.

Leisure Information / Intensity of Activities - MAQ and NHANES III were more closely related as both assessed frequency of popular moderate- to high-intensity leisure activities, whereas LOPAR assessed larger range of intensities including daily living and hours spent sleeping and in very light and light activities.

DPP Cohort vs NHANES III - activity levels for DPP participants were greater than NHANES III participants that had impaired glucose tolerance; this may be influenced by study inclusion criteria and that the NHANES III cohort was a random sample of general population whereas DPP was volunteer sample committed to an intervention study.

What conclusions can we take from this research?
The three questionnaires, whilst different, provided an insight into physical activity behaviours for participants at risk of developing diabetes compared to general USA population. Participants at risk of developing diabetes were less physically active than the general population however, when matched for impaired glucose tolerance they were more active than participants in the NHANES III subgroup. This is likely an effect of being in a study and being observed and monitored.

Physical activity was adversely affected by measures of obesity whereby participants with higher BMI and waist: hip ratio were less active.

Self-reporting of physical activity can present chances for participant bias and over-reporting of data however, surveys conducted over longer periods of time can better capture normal activity behaviours. Surveys that include detailed or specific questions and are restricted to specific activity intensities are likely to provide improved and more valid results.

Practical advice
Results from this study and other resources, support the premise that people at risk of developing diabetes should partake in regular physical activity of various forms and intensities. Physical activity can help insulin and weight management, lower blood pressure and reduce risk of stress and heart disease and should be prescribed in a controlled manner. Establishing positive activity habits earlier in life is recommended to help address, reduce and aid the fight against diabetes.

Application of results from this study to other populations needs to consider variables including gender, age, ethnicity, anthropometry and glucose tolerance.

Further information/resources
-       https://www.diabetes.ca/en-CA/health-care-providers/clinical-practice-guidelines/chapter-10#panel-tab_FullText

-       Diabetes & Exercise Safety, Flood, Lisa MSN, RN, CS; Constance, Ann MA, RD, CDE

-       https://www.ndss.com.au/living-with-diabetes/health-management/exercise/

References

1.   Diabetes Globally (2022) Diabetes Australia

< https://www.diabetesaustralia.com.au/about-diabetes/diabetes-globally/ >

2.   Diabetes in Australia (2022) Diabetes Australia < https://www.diabetesaustralia.com.au/about-diabetes/diabetes-in-australia/

3.   Metformin (2022) Mayo Foundation for Medical Education and Research

< https://www.mayoclinic.org/drugs-supplements/metformin-oral-route/side-effects/drg-20067074?p=1#:~:text=Metformin%20is%20used%20to%20treat,where%20it%20can%20work%20properly >

4.   Rosenman, R., Tennekoon, V, and Hill, L.G. (2011) Measuring bias in self-reported data. Int J Behav Healthc Res. Oct; 2(4): 320–332

< https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4224297/ >

5.    Physical activity (2022) National Diabetes Services Scheme

< https://www.ndss.com.au/living-with-diabetes/health-management/exercise/ >