African American women born at a low or very low birth weight may be at a higher risk for developing type 2 diabetes. The findings, which appear in Diabetes Care, may explain in part the higher occurrence of type 2 diabetes in African American populations, which has a high prevalence of low birth weight.
Researchers from Boston University’s Slone Epidemiology Center followed more than 21,000 women enrolled in the Black Women’s Health Study over the course of 16 years, analyzing characteristics such as birth weight, current age, family history of diabetes, body mass index, physical activity and socioeconomic status.
The study results indicate that women with low birth weight had a 13 percent higher chance of developing type 2 diabetes than those with normal birth weight, and those with very low birth weight had a 40 percent higher chance of developing the disease. Low birth weight was defined as less than 2.5 kg, and very low birth weight as less than 1.5 kg. It appeared that body size did not play a role in this relationship as there was a clear association between birth weight and diabetes even for women who were not obese.
Although previous studies have shown that birth characteristics such as birth weight can have a major impact on adult health, this is the first large-scale study to demonstrate this effect in an African American population.
“African American women are at increased risk of developing type 2 diabetes, and also have higher rates of low birth weight than white women,” said Edward Ruiz-Narváez, ScD, assistant professor of epidemiology at Boston University School of Public Health. “Our study shows a clear relationship between birth weight and diabetes that highlights the importance of further research for this at-risk group.”
Diabetes Risk in Black Women: Where You Live
A long-term study of African-American women’s health has revealed yet another factor, in addition to poor diet, lack of exercise, and low income, that amplifies the risk of adult-onset diabetes. Yvette Cozier, an epidemiologist at the Slone Epidemiology Center and an assistant professor of epidemiology at the School of Public Health, says that where a woman lives may also add to the likelihood of her developing the disease.
The new study, which appears online in the American Journal of Epidemiology, is the first to determine if, and how, the type of area an African-American woman lives in contributes to her chances of developing type 2 diabetes. Cozier and her colleagues found that the rate of new type 2 diabetes for women in neighborhoods with average incomes of $15,000 was one and a quarter times that of women in neighborhoods with average incomes of $100,000. When they compared rates in the lowest income neighborhoods to rates in the highest, the number of women diagnosed with type 2 diabetes was 1.65 times higher in the former. They found that the discrepancy exists even among women who have more education and earn more money than their low-income neighbors.
Characterized by an inability to metabolize sugar because the hormone insulin becomes ineffective, type 2 diabetes affects 20.6 million people in the United States and accounts for 9 out of 10 cases of all diabetes. (In type I diabetes, the problem is low insulin, not ineffective insulin). Since 1995, Cozier and her colleagues working on the Black Women’s Health Study have followed the health of 46,382 participants between the ages of 30 and 69.
The results support what Cozier had long suspected: that no matter how well a black woman takes care of herself, her neighborhood may be undermining her health. A lack of available fresh produce, nonexistent recreation areas for exercising, and a proliferation of fat-laden fast food franchises all contribute to obesity, the main culprit in type 2 diabetes. Some less obvious factors include such things as poorly lit streets and high crime, which discourage even the most active women from the simple exercise of going out for a walk. And the sum total of these increases stress, another risk factor.
Sedentary and overweight African-American women over 40, especially with excess fat around the middle - in clinical parlance, “apple shaped” - are the most likely to develop type 2 diabetes, and those with a family history are at greater risk. People with Hispanic, Native American, or Asian backgrounds are also more likely to develop type 2 diabetes in connection with obesity, according to the American Diabetes Association.
type 2 diabetes in African American women" align="right" /> According to the researchers, there are two leading hypotheses for the phenomenon. The first, known as the “thrifty phenotype hypothesis,” states that once the newborn body perceives that it lacks nutrition, it reprograms itself to absorb more nutrition, causing an imbalance in metabolism that eventually leads to type 2 diabetes. The second, known as the “fetal insulin hypothesis,” states that genes that are responsible for impaired insulin secretion also have a negative effect on birth weight. Some of these genes have been discovered in recent studies, supporting the latter hypothesis.
Funding for this study was provided by grants from the National Institute on Minority Health and Health Disparities, the National Cancer Institute and the American Heart Association.
Treatment and Care for African Americans
Compared to the general population, African Americans are disproportionately affected by diabetes:
4.9 million, or 18.7 percent of all African Americans aged 20 years or older have diabetes.
African Americans are 1.8 times more likely to have diabetes as non Hispanic whites.
Diabetes is associated with an increased risk for a number of serious, sometimes life-threatening complications, and certain populations experience an even greater threat. Good diabetes management can help reduce your risk; however, many people are not even aware that they have diabetes until they develop one of its complications.
Blindness - African Americans are almost 50 percent as likely to develop diabetic retinopathy as non-Hispanic whites.
Kidney Disease - African Americans are 2.6 to 5.6 times as likely to suffer from kidney disease.
Amputations - African Americans are 2.7 times as likely to suffer from lower-limb amputations.
Jenny Eriksen Leary
Boston University Medical Center