Impaired glucose tolerance (IGT), along with impaired fasting glucose (IFG), is recognised as being a stage before diabetes when blood glucose levels are higher than normal. Thus, people with IGT are at high risk of developing type 2 diabetes, although this does not always happen. In more than one-third of people with IGT blood glucose levels will return to normal over a period of several years.

Data on IGT is included in this report because IGT greatly increases the risk of developing type 2 diabetes, 1  and it is linked with the development of cardiovascular disease. 2   3  In addition, some of the best evidence on the prevention of type 2 diabetes comes from studies of people with IGT.

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Prevalence

Some 280 million people worldwide, or 6.4% of adults, are estimated to have IGT in 2011. The vast majority (70%) of these people live in low- and middle-income countries. By 2030, the number of people with IGT is projected to increase to 398 million, or 7.1% of the adult population.

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Age distribution

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The prevalence of IGT is generally similar to that of diabetes, but somewhat higher in the Africa and Western Pacific Regions and slightly lower in the North America and Caribbean Region.

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1 Shaw JE, Zimmet PZ, de Courten M, et al. Impaired fasting glucose or impaired glucose tolerance. What best predicts future diabetes in Mauritius? Diabetes Care 1999; 22 (3): 399 - 402.

2 Perry RC, Baron AD. Impaired glucose tolerance. Why is it not a disease? Diabetes Care 1999; 22 (6): 883-885.

3 Tominaga M, Eguchi H, Manaka H, et al. Impaired glucose tolearnce is a risk factor for cardiovascular disease, but not impaired fasting glucose. The Funagata Diabetes Study.  Diabetes Care 1999; 22(6): 920 - 924.