Prevalence

In an attempt to better describe and understand the burden of diabetic complications, this section presents data on the rates of myocardial infarction, stroke, diabetic nephropathy, diabetic peripheral neuropathy, lower extremity amputations and diabetic retinopathy. The results of each study are presented against the country in which it was conducted, although given the design and small size of some of the studies, the results should not necessarily be seen as being representative of that country.

The main principles in collating available prevalence data were:

1. Studies were identified through a detailed literature search, as well as contact with IDF member organizations.
2. Studies with e100 participants were included; where more than one study was available for a country, preference was given to larger and population-based studies, those published after 1989, and those with the fewest restrictions.
3. Prevalences are reported for myocardial infarction, stroke, retinopathy, neuropathy and nephropathy, and incidence and prevalence for lower extremity amputations.
4. Where possible, the age ranges of the populations are reported. Where the age range of the population was not available, the mean or median age is reported.
5. Diagnostic criteria for each complication are recorded, as variation in definitions can affect the prevalences reported.
6. For some countries, results from more than one study are presented. This is usually because they cover different aspects of the diabetic population.

There are some important differences between these data and the estimates on diabetes prevalence and IGT. The total numbers of individuals within a country who may have complications are not estimated, nor is a national prevalence. Furthermore, data have not been projected from one country onto other countries. This is for two reasons: firstly, such calculations require knowledge of the age and sex structure of both the original study population, and of the target (national diabetic) population. In most cases, neither of these is known. Secondly, many studies are clinic based, and so their generalizability is limited.

Any conclusions about the burden of disease attributable to diabetic complications must be very guarded, and comparisons between different parts of the world should be extremely cautious. It must be noted that the interpretation of these studies of diabetic complications is severely hampered by the lack of population-based studies, and the wide variability in study design. Nevertheless, the data from EURODIAB would indicate that at least for some complications in type 1 diabetes, genuine differences exist between countries. What is absolutely clear from this review is that there are large parts of the world for which there are no useful data, and that there is a great need for population-based studies, using standardized protocols so that meaningful estimates of the prevalence of diabetic complications can be made.

Further details of the methodology and discussion of results are available in the Diabetes Atlas, second edition.

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