With no pill or medicine in sight to delay or prevent the development of dementia, researchers are finding promise in such lifestyle factors as diet, exercise and social stimulation.

The stakes are high. An estimated 5.8 million older Americans have some form of dementia, a degenerative brain disease that robs people of their memories and ability to perform basic tasks. Many require near constant attention, which drains the finances and emotional health of caregivers. And while deaths from heart disease are declining nationally, those attributed to Alzheimer’s dementia are spiking.

Two major clinical trials are underway to provide the scientific basis for what has been observed in less rigorous studies — that specific foods as part of an overall healthy diet as well as physical and mental activities and control of risk factors for heart and vascular disease will protect memory and thinking during aging.

One trial will compare cognitive test scores over three years of hundreds of older adults who follow a relatively new regimen called the MIND diet to those following a standard diet. None of the participants at either test site — Rush University Medical Center in Chicago and Harvard School of Public Health — had dementia at the outset.

The MIND diet emphasizes leafy greens — such as kale, collards, spinach and lettuce — over other vegetables, strawberries and blueberries over other fruits, and olive oil over butter or margarine. It limits red meat, cheeses, sweets and fried and fast foods. It was developed by researchers led by Martha Clare Morris, a Rush nutritional epidemiologist who died of cancer Feb. 15. She worked for more than 20 years on the relationship between nutrition and dementia, carefully analyzing which foods had the most impact on brain health.

In 2015, “Alzheimer’s & Dementia” published her study results showing older adults who rigorously followed the MIND diet were the equivalent of 7.5 years younger cognitively than those who followed it least. Two years later, another study showed refined results — those who ate one serving per day of leafy greens were the equivalent of 11 years younger cognitively than those who rarely or never ate them.

“The study results do not prove that eating green leafy vegetables slows brain aging, but it does show an association,” Morris said at the time. She also had observed that while strictly following the MIND diet yielded the best results, moderate adherence still lowered the risk of developing dementia. She did not find a similar result for moderately adhering to the two diets — DASH and Mediterranean — from which MIND was derived. DASH stands for Dietary Approaches to Stop Hypertension and MIND stands for Mediterranean-DASH Diet Intervention for Neurodegenerative Delay.

Dr. Klodian Dhana, an assistant professor in Rush’s department of internal medicine, said researchers focused on food groups affecting dementia that were not emphasized in either the DASH or Mediterranean diets. Eating more leafy greens and strawberries, for example, produced a higher score (less cognitive decline) on a scale Morris developed. A diet heavier on butter, cheese and pastries scored lower.

“The aim is to prevent dementia or at least to postpone it. We’ll see how participants change each year,” Dhana said of the trial set to conclude at year’s end. “Nearly all decline, but some more than others.”

The other clinical trial — called U.S. POINTER (U.S. Study to Protect Brain Health Through Lifestyle Intervention to Reduce Risk) and funded by the Alzheimer’s Association — involves numerous lifestyle “interventions” in older adults at risk of cognitive decline. At five locations around the country, participants will be evaluated on how diet, exercise, social stimulation and self-management of risk factors for heart and vascular disease affect brain health.

Kay Manning is a freelance writer.