Study: Memory Decline Between Ages 60 and 69 Is Linked to an Increased Risk of Stroke

Some memory lapses are an expected part of aging. However, adults in their 60s who performed worst on tests of memory and thinking were more likely to experience a stroke in the following years. This association persisted even after researchers accounted for blood pressure, smoking, and diabetes, Planet Today reports. It was no longer observed among people aged 70 and older.

Thus, a simple battery of cognitive tests could serve as an early warning sign of stroke, although only during one decade of life.

Alice Askemyr of Lund University in Malmö, Sweden, led the study alongside three colleagues. The team followed participants over an extended period without testing any treatments, so the study demonstrates an association between lower scores and subsequent strokes rather than showing that one causes the other.

The volunteers were recruited from the Good Aging in Skåne project, a long-running study of older adults in southern Sweden. Researchers randomly selected participants from population registers in five municipalities and first assessed them in 2001, 2007, or 2012.

All participants were aged 60 or older. None had dementia, a previous stroke, or a transient ischemic attack (TIA) — a temporary blockage of blood flow to the brain that usually resolves within minutes. This left 4,912 people in the study.

Each participant completed a series of standard tests. Some assessed memory, including the ability to recall and recognize a list of words. Others measured processing speed through simple visual tasks, such as crossing out numbers on a page or comparing patterns. Additional tests asked participants to name as many animals or occupations as possible or repeat numbers in reverse order.

The team combined the results of all the tests into a single overall score and then divided participants in each age group into three groups according to their scores.

Stroke data were obtained from the Swedish National Patient Register, which covers inpatient and specialist care. Over an average follow-up period of 12.3 years, 572 people experienced a first stroke.

The clearest pattern emerged among people aged 60 to 69, who were followed for an average of about 14 years. Before any adjustments were made, 119 people in the lowest third of the overall score distribution had experienced a stroke, compared with 44 in the highest third. The two groups were almost the same size, with approximately 1,030 people in each.

Researchers then adjusted for age, sex, education, physical activity, weight, smoking, and alcohol consumption. They also accounted for stroke risk factors, including diabetes, blood pressure, cholesterol levels, heart disease, and arrhythmia, as well as the medications participants were taking. Even after these adjustments, the group with the lowest scores had an 86% higher risk of stroke than the group with the highest scores.

A similar pattern was observed for memory. Participants in the lowest third of memory scores had a 68% higher risk of stroke, while those who performed slowest on processing-speed tests had a 66% higher risk.

The researchers found no clear association between stroke and tasks involving word or number fluency. Among the measures associated with stroke, the overall score showed the largest difference. When the data were analyzed by sex, the association was observed mainly in men, although the authors consider this a preliminary finding rather than a definitive result.

Among people in their 70s and 80s, lower scores did not predict a higher risk of stroke after the researchers accounted for the same factors. In an interview with Earth.com, Askemyr said the team had already expected the pattern to vary by age.

“The aging population is very diverse, and it becomes even more diverse with each passing decade,” she said. “You could simply say that people aged 60–69 are more comparable to one another than a group of people aged 80 and older.”

She explained that older people differ more widely in their health conditions and the medications they take. Some also die from other causes earlier, making it harder to identify risk factors.

“It is easier to identify associations in the younger age group, and we cannot say with certainty that these patterns are completely absent in the older age groups,” she added.

The researchers point to one possible explanation: damage caused by problems in the brain’s small blood vessels that a person may never notice.

“So-called ‘silent’ brain injuries can affect both cognitive function and future stroke risk,” Askemyr said. “They affect approximately 70% of adults over the age of 70, so their effects may be easier to detect in people in their 60s, when such injuries and other factors affecting cognitive function, including illnesses and medications, are less common.”

The team did not examine brain scans in this analysis, so this hypothesis was not tested.

The authors noted that people who participated in the study were probably healthier than those who did not. Askemyr also pointed out that the findings may not apply to countries with different healthcare systems and lifestyle habits.

Some participants in the lowest-scoring group may already have been in the early stages of dementia. Among people in their 60s, dementia was subsequently diagnosed in 6.2% of those in the lowest third, compared with 1.6% of those in the highest third. The researchers may also have classified some minor strokes as transient ischemic attacks and excluded them, since computed tomography (CT) was the standard method of stroke diagnosis in Sweden for much of the study period.

Askemyr emphasizes that anyone who notices a decline in memory should consult a doctor. Some changes in memory are expected with age, she added. However, they may also signal excessive stress, insufficient sleep, medication side effects, or an underlying medical problem.

According to Askemyr, the Good Aging in Skåne project is ongoing. It continually recruits new participants and follows up with previous participants, while stroke is just one of the conditions it monitors.

“Over time, of course, it will be possible to determine whether even more study participants have experienced a stroke,” she said.

The authors wrote that, to their knowledge, no previous study had compared brain scans of people with lower cognitive scores with scans of people who went on to experience a stroke later in life. They hope the next step will involve brain-imaging studies, as well as research in younger populations to determine whether cognitive test results, combined with other medical measurements, can identify people at higher risk.

Until then, the question of why lower cognitive scores in people's 60s are associated with a greater number of strokes remains unanswered.