Type 2 Diabetes Glycemic Control From 1988 to 2000, Better But Worse?
posted 01/06/04
Diabetes is controlled in only 36% of the participants, despite recommendations for early diagnosis and aggressive treatment in recent years.

The purpose of the study was to describe the changes in demographics, antidiabetic treatment, and glycemic control among the prevalent U.S. adult diagnosed type 2 diabetes population between the National Health and Nutrition Examination Survey (NHANES) III (1988–1994) and the initial release of NHANES 1999–2000.

The study population was derived from NHANES III (n = 1,215) and NHANES 1999–2000 (n = 372) subjects who reported a diagnosis of type 2 diabetes with available data on diabetes medication and HbA_1c. Four therapeutic regimens were defined: diet only, insulin only, oral antidiabetic drugs (OADs) only, or OADs plus insulin. Multiple logistic regression was used to examine changes in antidiabetic regimens and glycemic control rates over time, adjusted for demographic and clinical risk factors. The outcome measure for glycemic control was HbA_1c. Glycemic control rates were defined as the proportion of type 2 diabetic patients with HbA_1c level <7%.

The results showed that dietary treatment in individuals with diabetes decreased as the sole therapy from 27.4 to 20.2% between the surveys. Insulin use also decreased from 24.2 to 16.4%, while those on OADs only increased from 45.4 to 52.5%. Combination of OADs and insulin increased from 3.1 to 11.0%. Glycemic control rates declined from 44.5% in NHANES III (1988–1994) to 35.8% in NHANES 1999–2000.

It was concluded that treatment regimens among U.S. adults diagnosed with type 2 diabetes have changed substantially over the past 10 years. However, a decrease in glycemic control rates was also observed during this time period. This trend may contribute to increased rates of macrovascular and microvascular diabetic complications, which may impact health care costs. Our data support the public health message of implementation of early, aggressive management of diabetes.

Our findings show that the proportion of adults in the U.S. with adequately controlled, diagnosed type 2 diabetes decreased between 1988 and 2000. Diabetes is controlled in only 36% of the more recent survey participants, despite recommendations for early diagnosis and aggressive treatment in recent years. We also observed changes in the demographic distribution of the adults with diagnosed type 2 diabetes from NHANES III (1988–1994) to NHANES 1999–2000, such as an increased proportion of men and minority groups other than non-Hispanic blacks and Mexican Americans. In recent years, individuals with diagnosed diabetes tended to be younger, to weigh more, and to have a longer duration of diabetes. However, we found that these demographic differences did not fully explain the lower glycemic control rates seen in recent years. Other reasons might account for the observed declining rates over time, such as changes in patient compliance with treatment programs despite more aggressive management. Another possible explanation for this observation may be surveillance bias due to a preferential increased screening for diabetes in high-risk individuals in the late 1990s compared with the previous decade.

In addition to changes in demographic features among patients over time, we also observed changes in the therapeutic regimen. The proportion of current individuals with diagnosed diabetes following diet-only or insulin-only treatment regimens has decreased since 1988–1994, but the proportion receiving OADs only or OADs in combination with insulin has increased. This change may be due to a larger selection of marketed oral agents. The increase in use of OADs from 1994 to 2000 is likely because only sulfonylureas were available in the earlier time period. By 2000, at least six new products in four new classes of OADs had become available. Another reason for the observed change may be a trend toward more aggressive and earlier treatment with OADs and OAD/insulin combinations.

We have also demonstrated that glycemic control was better in older individuals with diagnosed diabetes, those with higher BMI, and those with a longer duration of diagnosed diabetes. Diabetic control was worse in minority ethnic groups and those taking medications (as compared with those on diet only). It is not clear why glycemic control might be better in older individuals, but some studies have suggested that older patients may have better access to medical care, are more motivated to receive care, and are more compliant with medication use. This finding is somewhat in contrast to that of the U.K. Prospective Diabetes Study (UKPDS), which suggested that glycemic control rates among individuals with diabetes decrease with disease duration and, thus, with age. Also in contrast to the current study, Harris et al. found that obesity was not related to glycemic control. They attributed their results to the cross-sectional design of the survey.

We conclude that the proportion of adults in the U.S. with diagnosed type 2 diabetes that is controlled is inadequate and less favorable than in previous years. The cardiovascular and other consequences of inadequate glycemic control warrant serious consideration by treating physicians and others who care for individuals with diabetes. These data lend support to public health initiatives advocating early and aggressive management of diabetes.

Source: Diabetes In Control.com: Diabetes Care 27:17-20, 2004.

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