Something new to worry you: A new study finds that certain chronic viral infections — including the common herpes simplex virus — contributes to cognitive decline in healthy older adults.

Worldwide, some 417 million people under the age of 50 have the herpes simplex virus, associated with genital herpes.

For the new study, published in the journal Alzheimer's Disease and Associated Disorders, Dr. Vishwajit Nimgaonkar, of the University of Pittsburgh School of Medicine in Pennsylvania, tracked 1,000 adults over the age of 65 years who were evaluated annually for five years to detect any cognitive change and examined blood samples for viral exposures.

The results showed exposure to herpes simplex virus 2 (HSV), cytomegalovirus (CMV), and the protozoa Toxoplasma gondii — a parasite found in cat feces — were linked with aspects of cognitive decline typically considered to be age-related decline, Medical News Today reports.

"Our study is one of the few to assess viral exposure and cognitive functioning measures over a period of time in a group of older adults," Dr. Nimgaonkar said. He added that it is possible that these viruses "are triggering some neurotoxic effects."