Elderly cognitive function, long believed to be a separate from childhood, may be connected to cognitive ability developed as a child, a new study finds.

The longitudinal study compared the IQs at age 11 and 70 of 588 participants, in addition to cortical thicknesses measured at age 73. The brain's health can be measured by the cortical thickness; just like muscles, the more a section of the brain is used, the larger it grows.

Researchers have found that preserving the brain's cortical thickness while young can lead to better cognition once older. They discovered that cognitive ability as a child accounted for more than two-thirds of cognitive ability and cortical thickness in old age.

"It appears that aging well cognitively is not strictly due to something that one does or does not do in old age but rather, the end point of things that have been going on throughout one's life," Dr. Sherif Karama, lead author of the study and assistant professor of clinical psychiatry at McGill University, told Time.

Due to research constraints, it's rare that a study on the elderly includes information from their childhood. But even though IQ tests are a controversial form of measurement, people who try to learn and experience more, grow thicker cortexes. Karama also suggests a gene exists which is responsible for intelligence. This purported gene manifests as a desire to learn, and consequently, leads a person to engage in activities promoting cortical maintenance.

These factors considered, the people who showed less cognitive function as older adults could have just started off with thinner cortexes early on, giving them less gray matter to preserve. The researchers say it's still unclear if there is a correlation between cortical thickness and IQ.

Although participants who developed full-blown dementia were excluded from the study, the findings may still have repercussions for those concerned about developing dementia. "Some data does indeed suggest that [higher intelligence] postpones its manifestation," Karama told Time.

Dementia is the name for a number of symptoms that affect the aging brain, including memory loss, irritability, personality changes, and inability to control emotions. Alzheimer's disease is the most common form dementia among many. About one out of every eight people ages 65 and older have the disease, and almost half of all people ages 85 are afflicted, according to the National Institutes of Health.

Source: Karama S, Bastin M, Murray C. Childhood cognitive ability accounts for associations between cognitive ability and brain cortical thickness in old age. Molecular Psychiatry. 2013