To be lonely is to be “destitute of sympathetic or friendly companionship,” according to one dictionary definition.

A recent meta-analysis examining data from more than 600,000 people suggests that loneliness increases dementia risk. Those who reported feeling lonely were 31 percent more likely to develop dementia than those who did not, according to the findings.

“It differs from being alone or isolated,” researchers wrote in the study, published in Nature Mental Health. “People can feel lonely even when with others if the quality or quantity of their social connections does not meet what is needed or desired.”

Key Findings

The researchers analyzed 21 previous studies, with 13 showing a “significant association” between loneliness and dementia risk. The analysis revealed specific links to various forms of dementia, including Alzheimer’s disease.

Depression and social isolation were identified as underlying causes of loneliness. Loneliness is closely associated with depressive symptoms, which increase the risk for cognitive decline, the researchers wrote.

“Feeling lonely is also related to reduced engagement in social activities and poor social interactions,” they wrote. “It is plausible that reduced social participation reduces cognitive stimulation, leaving individuals who experience loneliness more vulnerable to cognitive decline.”

Other observational studies have found the same link between dementia and loneliness, which spurred these researchers to review the literature. For example, a 2022 study published in International Psychogeriatrics based on 15 years of following up on dementia patients found that loneliness was linked to a nearly 60 percent increased risk of all-cause dementia.

The Mechanisms Behind the Connection

The results are not surprising, Martina Luchetti, the study’s lead researcher and assistant professor of behavioral sciences at Florida State University College of Medicine, said in a statement.

The relationship between loneliness and dementia begins long before diagnosis, she said.

“Dementia [involves] neuropathological changes that start decades before clinical onset,” Luchetti stated. “Loneliness—the dissatisfaction with social relationships—may impact how you are functioning cognitively, and in daily life.”

Loneliness is closely linked to cognitive decline for several reasons, Mark Mayfield, an assistant professor of counseling at Colorado Christian University who was not affiliated with the study, told The Epoch Times. These include the following:

• Stress response: “Chronic loneliness triggers prolonged stress, which raises levels of cortisol, a hormone that affects the brain’s cognitive functioning over time,” Mayfield, author of “The Path Out of Loneliness,” said. “This chronic stress can lead to inflammation and damage areas like the hippocampus and prefrontal cortex, which are essential for memory and executive function.”
• Social stimulation: Another reason for the association between loneliness and decline in brain health, according to Mayfield, is that cognitive health thrives on stimulation derived from social interaction. “Loneliness often leads to social isolation, depriving individuals of these interactions, which are critical for maintaining mental agility,” he said.
• Depression: Another prominent link between loneliness and cognitive decline is depression. The relationship appears to be bidirectional—loneliness may lead to depression, or depression may cause loneliness, creating a cycle that contributes to cognitive decline. “Depression, often a byproduct of loneliness, has been identified as a risk factor for dementia,” Mayfield said. “Loneliness may worsen depressive symptoms, which can contribute to the overall cognitive decline seen in dementia patients.”

Public Health Implications

The scale and scope of this research—encompassing data from over half a million people—underscores that loneliness is not merely an emotional concern but a significant public health issue, according to Mayfield.

“The study provides scientific backing to the notion that loneliness is not just an emotional state but a public health issue with significant physical and mental consequences, including dementia,” he said. “This awareness can motivate individuals and caregivers to take loneliness seriously and seek proactive measures.”