Older adults with a reduced sense of smell are more likely to develop dementia. Sensory impairment, which also includes loss of hearing, vision, or touch, accelerates cognitive decline directly or indirectly.

After exercise, the liver secretes the protein Gpld1, which improves cognitive function in aging mice. Overproducing the amount of Gpld1 in mice conferred the same brain benefits as exercise.

Transfers of the immune cell eosinophils from young mice into old mice resolved inflammation, rejuvenated the immune system, and improved body composition and physical fitness.

The hormone fibroblast growth factor 21 is made in the liver in response to increased levels of sugar; it targets glutamatergic neurons in the brain to lower sugar intake and cravings for sweets.