Neuroscientists know that there is a link between loneliness and cognitive decline in older adults, although it is still difficult to understand the exact magnitude of the link. A new longitudinal study provides evidence that a proportion of people who feel lonely end up having more memory impairment, though this doesn't necessarily mean that their brains age faster.

The report, published in Aging & Mental Health, shows that older adults with higher levels of loneliness scored lower on tests of immediate and delayed recall. Even so, the rate at which their memory declined over six years was virtually identical to those who were not lonely.

“It suggests that loneliness may play a more prominent role in the initial state of memory than in its progressive decline,” said Luis Carlos Venegas-Sanabria of the School of Medicine and Health Sciences at Universidad del Rosario, who led the research. “The study underscores the importance of addressing loneliness as a significant factor in the context of cognitive performance in older adults.”

Six-Year Study of Thousands of Single People

The team analyzed data from the Survey of Health, Ageing and Retirement in Europe (SHARE), one of the most robust longitudinal databases for studying aging. For six years, the researchers followed 10,217 adults, aged 65 to 94, from 12 European countries. They assessed their level of loneliness and their performance on memory tests.

The results show that age was the most important determinant of memory level and speed of decline. From the age of 75 onwards, scores began to fall more rapidly. After 85 the decline became more pronounced. Depression and chronic diseases such as diabetes also reduced the initial score. Loneliness, while influencing the starting point, did not accelerate the slope of cognitive decline.

The study also found that physical activity was associated with better initial memory scores. People who engaged in moderate or vigorous physical activity at least once a month recalled more words on immediate and delayed recall tests. This effect did not change the speed of decline, but it did raise the baseline level, which functions as a kind of “cognitive buffer.”

Although the study does not explore the causes of the link between loneliness and cognition, previous research has proposed plausible mechanisms. Loneliness is often associated with less social interaction, a factor that influences cognitive performance. It is also associated with increased risk of depression, which does directly affect memory tests. In addition, lonely people tend to have more health problems, such as hypertension or diabetes, which also affect cognitive function.

By 2050, according to United Nations projections, one in six people in the world will be over the age of 65. Societies are entering a stage where old age will no longer be the exception but will become the norm. Dementia, as well as other neurodegenerative diseases that appear with age, will be a major challenge for health care institutions.