But when his father was diagnosed with the disease about five years ago, he went to the Alzheimer’s Prevention Clinic in New York to see what he could do.

Though he had no noticeable memory issues, cognitive testing showed less than ideal levels in certain areas. His neurologist told him there were a number of lifestyle changes that might help his cognition and possibly reduce the risk of developing Alzheimer’s disease.

Mr. Chambers, a 48-year-old physical therapist in Jersey City, N.J., modified his sleep, diet and exercise routines. Eighteen months later, his performance on a battery of cognitive tests improved, particularly in areas like processing speed and executive function, such as decision-making and planning.

“I feel a certain sense of comfort in knowing that there are factors that I can control that can contribute to the decreased risk of me getting Alzheimer’s,” says Mr. Chambers.

Mr. Chambers is among 154 patients in a study, published Wednesday in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association, that doctors say shows encouraging results. Among healthy patients, people who made changes in nutrition and exercise showed cognitive improvements on average. People who were already experiencing some memory problems also showed cognitive improvement—if they followed at least 60% of the recommended changes.

It’s unclear whether the lifestyle changes can actually help prevent the development of Alzheimer’s disease, or simply improve cognition.

“This is a therapeutic approach that was shown to not only maintain, but improve cognition in people with the earliest stages of Alzheimer’s,” says Richard Isaacson, a neurologist and first author on the study.

While researchers struggle to develop a drug to treat or cure Alzheimer’s, some doctors are recommending lifestyle changes. Dr. Isaacson began developing personalized prevention plans for patients of all ages in 2013 when he started the Alzheimer’s Prevention Clinic at Weill Cornell Medicine and NewYork-Presbyterian, of which he is now director.

Alzheimer’s disease starts in the brain some 20 to 30 years before symptoms emerge, so intervening early through personalized medicine and lifestyle changes can make a difference, says Dr. Isaacson.

For the study, Dr. Isaacson and co-researchers enrolled 154 patients, who ranged in age from 25 to 86, in two groups. There was a small group of 35 patients with mild cognitive impairment (MCI), often a precursor to dementia, and a larger group of 119 patients who had no symptoms of memory loss, though some had less-than-ideal performance on cognitive tests.

Based on a battery of blood, genetic and cognitive tests, as well as measurements of their body fat and muscle mass, patients received a couple of dozen personalized recommendations ranging from eating specific types of fish and berries, to taking certain vitamins, and tailored exercise plans.

Eighteen months later, they took a series of very sensitive cognitive tests which may detect cognitive decline before memory problems outwardly appear, says Dr. Isaacson. The majority of both groups of patients showed statistically significant improvements when compared with their baseline, as well as compared with historical control groups.

Most surprising, says Dr. Isaacson, is that the MCI patients who followed at least 60% of their recommendations showed cognitive improvement. However, MCI patients who followed less than 60% of the recommendations experienced cognitive declines similar to the control groups, he notes.

In the larger group of patients, everyone—including those who didn’t follow a large percentage of recommendations—performed better on the cognitive tests compared with their baseline and control groups 18 months later. On average, younger people showed more improvement on the cognitive tests compared with people over 60, says Dr. Isaacson. Patients in both groups had a family history of Alzheimer’s disease.

Researchers monitored cholesterol, blood pressure and blood sugar levels because they are linked to an increased risk of Alzheimer’s disease. And the study tracked patients’ body fat and muscle mass; studies show the memory center of the brain, called the hippocampus, gets smaller as belly size gets larger, says Dr. Isaacson. Patients were assigned exercises based on their body metrics. Other recommendations included targeting stress reduction through activities like meditation, and encouraging brain stimulation by learning a new instrument or foreign language.

Marwan Sabbagh, director of the Cleveland Clinic Lou Ruvo Center for Brain Health in Las Vegas, says the results are promising. “The people who had the targeted intervention and who were high in their adherence did very, very well over the span of 18 months, showing that these strategies work, and I think that’s a very encouraging result,” says Dr. Sabbagh of the study. “That is where the trend is going.” Read more at WSJ