By Morgan Jones
Just by taking a look around, one might see that obesity has become a bigger problem over the last several decades. But changes in diabetes rates are less easy to see.
Researchers behind a new study explored changes in rates of type 2 diabetes in the US during the past 20 years.
This study found that rates of diabetes have increased, and the condition now affects over 20 million adults.
"There has been a staggering increase in the prevalence of obesity over the past 30 years in the United States," wrote the authors of this study, which was led by Elizabeth Selvin, PhD, MPH, of the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland.
These authors wanted to explore how rates of type 2 diabetes, a condition often tied to obesity, might have also changed during the past several decades.
In particular, Dr. Selvin and team wanted to examine diabetes as defined by hemoglobin A1c, or HbA1c. This is a blood test for diabetes that provides information on a person's average blood sugar level during the previous three months.
To do so, the researchers used the National Health and Nutrition Examination Survey (NHANES) for the years 1988 to 1994 and 1999 to 2010 to identify 43,439 participants aged 20 and older. This survey recorded various types of data on participants, including results from blood tests, previous conditions and demographic information.
Using the participants' HbA1c levels, Dr. Selvin and team looked for instances of undiagnosed diabetes and prediabetes — when blood sugar levels are higher than normal, but not high enough to be considered diabetes. Among those who were already diagnosed with diabetes, control of their condition was also examined through participants' HbA1c levels.
Dr. Selvin and team found that the total rate of diabetes cases — determined by either an existing diagnosis or HbA1c levels high enough to warrant a diagnosis — increased from 6.2 percent of participants in 1988 to 1994 to 8.8 percent in 1999 to 2004, then up to 9.9 percent in 2005 to 2010.
Using this data, the researchers estimated that in the US in 2010, around 21 million people aged 20 and older had diabetes.
While the total number of diabetes cases increased over the study period, the number of undiagnosed cases saw no major change. Because of this finding, Dr. Selvin and team estimated that while 16 percent of diabetes cases were undiagnosed during 1988 to 1994, this proportion had dropped to 11 percent of cases by the study's end in 2005 to 2010.
Prediabetes increased from 5.8 percent of participants in 1988 to 1994 to 11.9 percent in 1999 to 2004, then up to 12.4 percent in 2005 to 2010.
While rates of diabetes increased, those with diabetes seemed to have better control of their condition as the study period went on, though certain ethnic groups seemed to have worse rates of control, including non-Hispanic blacks and Mexican Americans. Overall, an estimated 50.9 percent of people with diagnosed diabetes in 1988 to 1994 had their condition under control, a number which increased to 58.8 percent by the study's end in 2005 to 2010.
The researchers also found, as expected, that the obesity rates of survey participants increased substantially over the time period, leading them to conclude "that the increases in diabetes cases over the past 2 decades were largely explained by increases in obesity."
In an interview with dailyRx News, Deborah Gordon, MD, operator of an integrative medical practice based in Ashland, Oregon, said that dietary changes in the US are likely contributing factors behind the increase of both conditions.
"Diabetes and obesity trends (called "Diabesity" by Mark Hyman, MD) upwards over the last several decades have paralleled with a switch from animal fat to vegetable oils and a marked increase in sugars and refined carbohydrates — think anything from bread and juice to doughnuts and soda," said Dr. Gordon.
"A return to whole foods such as healthy proteins (meat, fish, dairy and eggs) with their inherent fats (eat the yolks, and opt for whole milk not skim) have shown the greatest promise in sustainable reversal of both diabetes and obesity," Dr. Gordon told dailyRx News.
It is important to note that participants in Dr. Selvin's study self-reported whether or not they had a diabetes diagnosis, and the study relied on only one test of HbA1c levels, which the researchers noted would be repeated in a doctor's office to confirm a diagnosis. Further research is needed to confirm these findings.
This study was published in the Annals of Internal Medicine on April 14.
Funding grants for the research were provided by the National Institutes of Health.