According to U.S. study, researchers examined prediabetes may increase patients' risk for heart and kidney disease. Researchers studied a nationally representative sample of 27,971 adults surveyed in four waves from 1988 to 1994, 1999 to 2004, 2005 to 2010 and 2011 to 2014. The study was published in The Lancet Diabetes and Endocrinology.

They estimated that the number of adults with prediabetes increased from 56.2 million at the start of the study period to 78.5 million by the end. Prediabetes was defined as a fasting blood glucose level of 100 to 125 mg/dL or a hemoglobin A1c level of 5.7% to 6.4%. By the end of the study, 37% of people with prediabetes had high blood pressure, 51% had dyslipidemia, 24% smoked, 5% had a reduced glomerular filtration rate, and 8% had elevated levels of urinary albumin.

While the study can not prove whether or how reducing slightly elevated blood sugar might reduce the risk of heart or kidney problems, lifestyle changes like increased exercise and a healthier diet might help people reduce blood sugar and their risk of health problems that can accompany diabetes said lead study author Dr. Mohammed Ali.

Limitations of the study include the potential that the diabetes assessments used might have underestimated the number of people with prediabetes, the authors note. Still, the results offer fresh evidence of the health risks associated with pre-diabetes, said Mika Kivimaki. However, the evidence is stronger for the connection with kidney disease than heart disease, Kivimaki said by email.

The author concludes that Obesity, elevated blood pressure, high cholesterol, and smoking are much more important risk factors for cardiovascular disease and are therefore the main targets of cardiovascular disease prevention. But people with slightly elevated blood sugar should still take steps to get it down to a healthy level.