More than 29 million Americans are living with diabetes, and 86 million are living with prediabetes.

Type 2 diabetes accounts for about 90 to 95 percent of all diagnosed cases of diabetes, and Type 1 diabetes accounts for about 5 percent. Cancer rates are higher in those with diabetes.

Between 8 and 18 percent of people who have cancer also have diabetes. A strong link exists between diabetes and different types of cancer.

For example, Type 1 diabetes often occurs with stomach and cervical cancers, and Type 2 diabetes often occurs with colon, liver, kidney, pancreatic, breast, and endometrial cancers.

Although studies in Type 2 diabetes do not prove that diabetes causes cancer, researchers have not been able to rule out that obesity may raise the risk for both cancer and diabetes. Obesity and diabetes are positively associated with meningioma, a benign tumor that may cause significant morbidity.

However, although many cancers are more common among those with diabetes, a study from The Ohio State University found that cancerous brain tumors are less common among those with elevated blood sugar and diabetes.

Why is the association between blood glucose levels and brain cancer the opposite of that for several other cancerous tumors?

The earlier Ohio State research showed that high blood sugar appears to reduce a person's risk of a noncancerous meningioma.

This cohort study evaluated the potential effects of obesity-related prediagnostic glucose, triglycerides, and cholesterol on meningioma and of prediagnostic meningioma on these biomarkers, which builds on previous Ohio State research, showing that high blood sugar reduces a person’s risk of meningioma. Both studies were led by Judith Schwartzbaum, an associate professor of epidemiology and a researcher in Ohio State's Comprehensive Cancer Center.

In this study, Schwartzbaum and colleagues identified 41,355 individuals in the Apolipoprotein MOrtality RISk (AMORIS) cohort with values for these biomarkers within 15 years before meningioma diagnosis, death, migration or the end of follow-up. Hazard ratios (HRs) and their interactions with time and age were estimated, using Cox regression.

The study results showed that meningioma was diagnosed in 181 women and 115 men whose median follow-up time was seven years. Fasting serum glucose level was inversely related to meningioma among women but not men. Prediagnostic diabetes was inversely related to meningioma in both sexes combined (HR=0.45, 95 percent confidence interval (CI) 0.29-0.71), as was serum cholesterol within the year before diagnosis (HR=0.50, 95 percent CI 0.34-0.72).

The study showed that hyperglycemia is inversely associated with meningioma in women, a finding that does not necessarily rule out the positive role of obesity or diabetes in meningioma development.

This finding may indicate that the effects of obesity or diabetes may depend on the stage of development and that the prediagnostic tumor may reduce serum cholesterol levels.

The relationship between blood glucose levels and brain cancer was strongest within a year of cancer diagnosis, suggesting that the tumor affects blood glucose levels or that elevated blood sugar or diabetes may be associated with a protective factor that reduces brain tumor risk.

Future research could address whether the sugar/tumor relationship can be modified to benefit brain cancer patients.