Researchers have long suspected that the more active a person is, the lower his or her risk of age-related cognitive decline and dementia, including Alzheimer’s disease. Studies have generally found good support for the relationship, but some rely on the participants to recall how active they’ve been. This method can be unreliable for a number of reasons, not the least of which is that people’s memories are not always dependable.

The people in the bottom 10% of intensity of activity were 2.8 times more likely to develop the disease as those in the top 1% of intensity level.

To avoid this issue, researchers in a recent study had 716 participants wear actigraphs on their wrists for 10 days so that their average activity levels could be calculated. Participants were an average of 82 years old when the study began and none was affected by cognitive decline. They took cognitive tests every year for an average of 3.5 years. At the end of the study period, 71 of the participants had been diagnosed with Alzheimer’s disease.

People who did the least amount of daily physical activity – those in the bottom 10% – were over twice as likely to have developed Alzheimer’s disease than people in the top 10%. The benefit of physical activity was even more pronounced for people who got some intense physical activity: The people in the bottom 10% of intensity of activity were 2.8 times more likely to develop the disease as those in the top 1% of intensity level.

Interestingly, the association held strong even after removing other variables from the equation, like body mass index (BMI), motor function, vascular diseases, chronic health conditions, and the APOE4 gene variant, which puts one at higher risk for Alzheimer’s disease.

It’s worth noting that the study does not actually show cause and effect. It’s possible, for example, that Alzheimer’s develops first and inactivity follows; or, perhaps, there is a third variable at play, which could lead to both inactivity and cognitive decline. However, given what we know about the neuroprotective effects of exercise – reducing inflammation, boosting the birth of new brain cells, and increasing blood flow to the brain – it seems more likely that exercise might also work reduce the risk of cognitive decline.

Lead author Aron Buchman stresses that the results are especially encouraging since they suggest that engaging in even the simplest activities may help reduce Alzheimer’s risk. He says in a news release that “activities like cooking, washing the dishes, playing cards and even moving a wheelchair with a person’s arms were beneficial. These are low-cost, easily accessible and side-effect free activities people can do at any age, including very old age, to possibly prevent Alzheimer’s.”

If the effects of exercise are cumulative, and doing the dishes or cleaning the house can help reduce one’s risk of cognitive decline, imagine what getting active in more significant ways, over the course of a lifetime, could do.

The study was carried out by a team at Rush University Medical Center, and published in the journal Neurology.