Exercise as it relates to Disease/Physical activity for the prevention of diabetes in adults with IFG

This Wikibooks page is a critique of the research article “Increased leisure-time physical activity associated with lower onset of diabetes in 44 828 adults with impaired fasting glucose: a population-based prospective cohort study” by Lao XQ et al., published in the British Journal of Sports Medicine in 2018.

What is the background to this research?
Diabetes is a chronic disease which affects the production and resistance of insulin in the body. Type 2 Diabetes makes up 85-90% of Diabetes cases and is associated with modifiable lifestyle risk factors, such as physical activity levels. Impaired Fasting Glucose (IFG) is an early detectable sign of deterioration of glucose metabolism and is a precursor to diagnosis of Diabetes. IFG is diagnosed with a Fasting Plasma Glucose (FPG) level ≥5.6mmol/L. Annually 6-9% of individuals with IFG progress to Diabetes. Physical activity has been shown to reduce the risk of Diabetes in individuals with Impaired Glucose Tolerance (IGT), a secondary late-stage precursor to Diabetes, however research on the effects of physical activity on the risk of Diabetes in individuals with IFG is minimal. The purpose of this study was to examine the effects of physical activity on the risk of Diabetes in individuals with IFG.

Where is the research from?
This research was conducted from data previously gathered between 1996 and 2014 by the MJ Health Management Institution in Taiwan through the MJ Health Screening Program. The study examined the self-reported and physician-reported data of 44,828 participants across this period. The study was published online in the British Journal of Sports Medicine on the 13th January 2018. The British Journal of Sports Medicine is a peer reviewed academic journal which publishes 24 journals a year in the field of sport and exercise medicine including physiotherapy, physical therapy, and rehabilitation.

What kind of research was this?
This study was a population-based prospective cohort study. This observational type study is suitable to study exposures which are rare, or when randomisation is not possible for practical or ethical reasons. Prospective cohort studies are typically accurate and efficient. However, these types of studies can be affected by selection bias when selecting the participants to study. This selection bias can be minimised by determining specific selection criteria prior to selecting participants. In this research article the authors determined their selection criteria in order to minimise any selection bias. Prospective cohort studies can also be susceptible to loss of participant due to follow-ups or withdrawals. These losses were accounted for in this study.

What did the research involve?
The participants in this study took part in a standard medical screening programme run by the MJ Health Management Institute in Taiwan. Between 1996 and 2014 the participants visited the Institute for a range of medical assessments administered by a medical practitioner, as well as completing self-assessed physical activity surveys. Between 1996 and 2014 a total of 248,481 participants visited the institution at least twice. From these participants the authors reviewed the history of participants who were identified as having IFG (FPG ≥5.6mmol/L). Participants who reported pre-existing physician-diagnosed cardiovascular and cerebrovascular disease were excluded from the study. Participants who lacked physical activity information were also excluded. From this participant selection the authors had a sample size of 44,828 participants with newly detected IFG. This selection methodology with specific requirements allowed the authors to minimise any selection bias in the study.

Participant data was then recorded across repeat Institution visits between 1996 and 2014 to assess the activity levels of participants and the incident rate of the onset of Type 2 Diabetes across the study period. The participants were grouped in to four levels of physical activity based on their self-reported leisure time physical activity habits: Inactive, Low, Moderate, and High physical activity.

Research Limitations
The methodology used to select and review the participants was effective for this study, however the limitation of this study is that the participant’s physical activity levels were self-reported. As the physical activity levels were not directly measured there is some area for doubt as to the complete accuracy of the data. Self-reported physical activity data can be over-reported with participants reporting higher levels of physical activity than their reality. For this study no other method of physical activity data collection would be feasible for a sample size this large. It must be considered therefore that some of the reported physical activity data could relate to lower levels than those recorded due to the self-reporting.

What were the basic results?
This study found that increased levels of physical activity reduced the risk and onset of Type 2 Diabetes in adults with IFG. The study found that individuals in the low physical activity category had a 12% reduction in the risk of developing Type 2 Diabetes compared to inactivity participants. The study found that participants with higher levels of physical activity had a further reduced risk, with participants with moderate levels of physical activity having a 20% reduction in risk of developing Type 2 Diabetes and participants with high levels of physical activity having a 25% reduction in risk. The study determined that the incidence of diabetic individuals would have been reduced by 19.2% if the inactive participants had performed at least 150 minutes of moderate-intensity physical activity per week, meeting the WHO physical activity guidelines.

The study also suggested that physical activity may reduce the risk of diabetes through reducing central obesity, improving glucose and lipid metabolism, and decreasing systemic inflammation. These suggestions are consistent with the findings of previous studies.

Furthermore, the study concluded that an increase in one activity level by the population of the Greater China area would correspond to a potential reduction of 7 million cases of Type 2 Diabetes.

What conclusions can we take from this research?
From this research we can conclude that physical activity can help to prevent the onset of Type 2 Diabetes, particularly in populations with IFG. Sedentary and low physical activity level populations should be encouraged to increase their levels of physical activity in order to receive health benefits and reduce the risk of developing Type 2 Diabetes. This would also reduce the costs on health care systems around the globe.

The findings of this study are consistent with the findings of a previous smaller study on the impact of physical activity on the onset of Type 2 Diabetes in individuals with IFG. The previous study found that the risk of developing Type 2 Diabetes was 35% lower in physically active individuals (compared with 19.2% reduction in this study).

The findings of this study are also consistent with studies on the effects of physical activity in adults with Impaired Glucose Tolerance (IGT). IGT is a similar pre-curser to Type 2 Diabetes, and is considered an advanced stage of pre-diabetes.

Practical Advice

 * People at risk of Type 2 Diabetes, or those diagnosed with IFG, should be physically active
 * Higher levels of physical activity provide the greatest reduction in risk of developing Type 2 Diabetes
 * Aim to meet the WHO minimum physical activity guidelines of 150 minutes of moderate-intensity physical activity a week
 * If you have, or are at risk of, Type 2 Diabetes consult your health care professional for advice before commencing physical activity

Further Readings

 * Diabetes Australia
 * World Health Organisation Global Recommendations on Physical Activity for Health
 * Australia's Physical Activity and Sedentary Behaviour Guidelines Fact Sheet: Adults (18-64 years)
 * Australia's Physical Activity and Sedentary Behaviour Guidelines: Tips and Ideas for Adults (18-64 years)