Guess what they found out? Those with these factors declined 22.5 percent more rapidly on cognitive test scores when compared to normal-weight individuals who presented with no metabolic abnormalities.

“Metabolic abnormality was defined as having two or more of the following risk factors: high blood pressure or taking medication for it; low HDL or ‘good’ cholesterol; high blood sugar or taking diabetes medication; and high triglycerides (a type of fat found in the blood) or taking medication to lower cholesterol,” according to a press release issued by the AAN.

So maybe listening to your doctor’s advice isn’t such a bad idea. Make it a point to get your numbers in check.

Low Levels of Vitamin D

Could low levels of vitamin D and cognitive decline be linked? The answer is yes.

A recent study published in JAMA Neurology shows that older adults who suffer from dementia often have low levels of vitamin D. Though researchers aren’t exactly sure why vitamin D affects mental decline, they have strong thoughts on the process in general.

"There is good evidence that vitamin D gets into all cells of the body, including the brain," says study author Joshua Miller, chair of the department of nutritional sciences at Rutgers University School of Environmental and Biological Sciences in New Brunswick, N.J., in an article published by U.S. News & World Report. One theory is that “vitamin D protects the brain from developing the plaques and tangles that are associated with Alzheimer's disease,” according to the article.

Miller says most people older than 75 in the United States are likely vitamin D-deficient. That’s a scary thing.

So no matter what your age, make it a habit to get adequate vitamin D. The Institute of Medicine says that you should have 600 IU of vitamin D daily.