The rate of diabetes in the United States has nearly doubled in the last ten years and the incidence of the disease has been particularly high in the South said a new report from the country’s Centers for Disease Control and Prevention (CDC) who suggest the main culprit is rising rates of obesity.

The figures, published in the 31st October issue of the CDC’s Morbidity and Mortality Weekly Report (MMWR), are the first to show a state-by-state breakdown of diagnosed diabetes incidence rate in adults.

The figures came from a telephone survey of more than 260,000 adults across the country who were asked if they had ever been diagnosed with diabetes and where that diagnosis took place. In 1995-97 the survey included 33 states although in 2005-07 it included 40 states. However, the study only shows comparisons for the 33 states.

The age-adjusted figures for 33 states show that the incidence of diabetes was 90 per cent higher in 2005-07 than in 1995-97, confirming fears that diabetes will continue to be a major public health problem in the US, said the CDC.

A number of factors are linked to increased risk of diabetes, including getting older, having less education, being physical inactive, being obese or putting on weight, and being in a racial/ethnic minority. The CDC report suggests that obesity is the main reason for the rise because the growth in diabetes prevalence matches the growth in obesity prevalence.

Although few diabetes incidence studies have been published, these figures are similar to those obtained in the Health Interview Survey (NHIS) that estimated diabetes incidence in 1997 to be 4.9 persons per 1,000, which compares with 4.8 per 1,000 in the CDC report and suggests that the incidence is rising.

The high incidence rates of diabetes in the South reflects previously documented rates for the region, which also shows higher rates of modifiable type 2 diabetes risk factors, including obesity and physical inactivity. 90 to 95 per cent of diabetes in the US is type 2.

An MMWR report earlier this year showed that the prevalence of obesity last year was highest in the South (27.3 per cent), followed by the Midwest (26.5) , the Northeast (24.4) and the West (23.1).

The current MMWR report cites a medical sports science study from four years ago where a similar pattern was found for physical inactivity, which was also highest in the South (17.4 per cent), followed by the Northeast (15.7), the Midwest (14.1), and the West (11.2).

The CDC said there should be more population-based approaches to reducing obesity and physical inactivity and helping those at high risk of developing type 2 diabetes, where research shows that a nearly 60 per cent reduction in risk can be achieved with a 5 to 10 per cent reduction in body weight combined with moderate exercise for 30 minutes a day on five days a week.

Some examples of programmes that could encourage weight loss and greater physical activity are better parks for walking in and more local walking trails, as well as giving people greater access to a wide range of healthy food.

The CDC also suggest continued surveillance and monitoring of diabetes, the risk factors and prevention efforts.

The current MMWR report does however have limitations in that it did not take into account improved rates of detection of diabetes, it relied on self- reports and it did not differentiate between type 1 and type 2 diabetes, which could distort the figures to some extent. Another reason is that the data might not be perfectly representative of the US population because the survey excluded people without a landline telephone, or who were living in a residential institution or on a military base at the time.

Another reason to treat these findings with a little caution is that only diagnosed cases of diabetes were included and therefore the true figure might be higher than those given here, plus the fact that the survey included only small sample sizes in certain states. Lastly, the survey response rate was quite low for some states (as low as 27 per cent for instance in the case of New Jersey), and that could also distort the figures.

More than 23 million Americans are living with diabetes and about 1.6 million new cases are diagnosed every year in the US said the CDC who also said that the disease was the 7th leading cause of death in the US in 2006.

“State-Specific Incidence of Diabetes Among Adults — Participating States, 1995–1997 and 2005–2007.”
KA Kirtland, YF Li, LS Geiss, TJ Thompson.
Div of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion, CDC.
MMWR, October 31, 2008 / 57(43);1169-1173.

Click here for the full MMWR report.

Sources: CDC.

Written by: Catharine Paddock, PhD.