Where does IDF get its information from for the statistics found in the Diabetes Atlas?
IDF gathers information from peer-reviewed journals, national health statistics reports, reports from international agencies such as the CDC and WHO (including STEPwise approach to surveillance reports), and from personal communication with investigators within the IDF network. These studies are then judged for quality and used to generate the estimates for diabetes found in the IDF Diabetes Atlas. Estimates for mortality and health expenditures rely on IDF prevalence data and other WHO figures to estimate the number of deaths and the medical costs attributable to diabetes.
When should I use national prevalence and how is this calculated?
The national prevalence is a percentage of the number of adults (20 – 79 years) who have diabetes in the given year (either 2014 or 2035) in a country or region. It is calculated by taking the number of cases in adults and dividing by the total population in adults. The national prevalence should be used when reporting statistics for just one country or region, or when the statistics being reported are not for comparison. If you are comparing one country or region to another, you should use the comparative prevalence.
When should I use comparative prevalence and how is this calculated?
The comparative prevalence allows us to adjust for the fact that there are different proportions of young and old people in different countries. In order to compare these countries, we take the national prevalence and make an adjustment to estimate what the prevalence would be for that country if the distribution of the population in different ages were different. The distribution that is used for this calculation is applied to all countries in the same way and is based on a 1998 distribution developed by the WHO in order to compare the relative burden of diseases in different countries.
What factors does IDF take into account when calculating the Atlas 2035 projections?
For projections, we only use changes in the predicted population and urbanization changes available from the UN Population Division. We do not include any predictions for changes in obesity or other risk factors. The projections are therefore quite conservative.
Are undiagnosed cases part of the number of cases for 2014 or in addition to the total?
Undiagnosed cases are already included in the total number of cases reported.
I notice that some of the national prevalence country data is less than the previous of the Atlas. Why is this?
The numbers of cases or the prevalence in a country may have decreased from previous editions because IDF was able to make some assumptions more precisely by utilizing better quality information. Lower figures are most likely due to a change in the source data (e.g. epidemiology studies, United Nations population estimates, World Bank income groups), and not due to an actual decrease in diabetes prevalence. Every country that has studies with consistent methodology over multiple years reports a consistent increase in diabetes.
Why has the prevalence and the absolute number of people with diabetes decreased in the Europe and Western Pacific region in 2014 compared to 2013?
New higher quality epidemiological studies conducted in Europe and the Western Pacific Region were published in 2014. Moreover, updated 2014 World Bank income group classifications and United Nations Urbanization were integrated into the model used to generate the estimates. Integrating these new data into the calculations resulted into lower comparative prevalence estimates for these two regions. The reasons for a decrease in the estimates in each particular country (due to either change in the epidemiological study, World Bank classification, or urbanization level) are complex. If you have any particular concern, contact the epidemiology team by e-mail [email protected] 
If the prevalence rates in some countries have decreased in recent years, how can IDF say that diabetes is on the increase?
Every country that has studies with consistent methodology over multiple years reports a consistent increase in diabetes. Our estimates may have decreased in some countries because we were able to make some of our assumptions more precise. Thus, actual numbers may change slightly but the overall trend is increasing for all countries.
What are the main factors, according to the Atlas, driving the diabetes epidemic?
There are a number of factors driving the diabetes epidemic but the most significant are those associated with type 2 diabetes: poor diet, less physical activity, and increases in life expectancy. We also note an increase in type 1 diabetes of around 3% a year in children, and the causes of this are still being investigated.
How does IDF propose we start to tackle this epidemic?
IDF has released a Global Diabetes Plan which outlines policies that will go far in preventing new cases of diabetes, providing good care to those with the diseases, and reducing the discrimination faced by those with diabetes. Countries must demonstrate their commitment to turning the tide on diabetes by implementing these policies across many sectors.