Two studies presented at the Alzheimer's Association International Conference® 2015 suggest an association between childhood school performance (age 9-10) and late life dementia. Other research reports identified loneliness, low physical activity and high TV viewing as risk factors for cognitive decline and dementia.

"Evidence is growing that there are lifestyle habits that you can adopt to maintain or potentially improve your health – including your brain health – as you age," said Heather Snyder, PhD, Alzheimer's Association Director of Medical and Scientific Operations. "Many of the habits are familiar. Often, the same healthful practices that are good for your overall health are also good for your brain. These actions and activities – controlling your heart health numbers, getting formal education, being physically and socially active – can help keep your brain and body healthy and potentially reduce your risk of cognitive decline. It's never too late or too early to start."

There is considerable variation among people diagnosed with dementia, including Alzheimer's disease, in the amount of amyloid plaques, tau tangles, inflammation and other damage in the brain. "Cognitive reserve" is a concept developed to explain the gap between the amount of brain damage and the level of memory and thinking symptoms the person experiences. It has been proposed that the greater the level of cognitive reserve, the higher the brain's ability to adapt to injury like that which causes dementia, and the more damage – and more time – required for cognitive function to decline far enough to be considered dementia. Formal education and occupational complexity have been viewed as the main contributors to cognitive reserve.

To further investigate and understand this notion, Serhiy Dekhtyar, PhD, Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden and colleagues followed 7,574 individuals aged 65+ from the Uppsala Birth Cohort Study (Sweden) for more than 20 years to detect their new cases of dementia. In addition to conventional measures of cognitive reserve, such as education and occupational attainment, they also collected data on childhood cognitive ability – school grades around age 10.

"We ended up with a full life-course model of cognitive reserve in dementia, with childhood cognitive ability, early-adulthood education, and mid-life occupational attainment, which has never been tested before," Dekhtyar said.

Dementia was diagnosed in 950 individuals. According to study results reported at AAIC 2015:

• Dementia risk was elevated 21% in people who were in the lowest 20% of childhood school grades in this population. Importantly, high occupational complexity could not compensate for the effect of low childhood school marks.
• Dementia risk was reduced 23% among individuals in occupations characterized by high complexity with data and numbers.
• Lowest dementia risk (39% reduction) was found in the group who had both higher childhood school performance and high occupational complexity with data.

"Our findings highlight the importance of early-life cognitive performance for the late-life risk of dementia. It appears that baseline cognitive ability – even at age 10 – may provide the foundation for successful cognitive aging much later in life," said Dekhtyar. "Formation of cognitive reserve is a process that apparently begins early in life."

Dekhtyar noted that these findings are corroborated in a smaller clinical study of dementia also conducted in Sweden.

At AAIC 2015, Hui-Xin Wang, PhD and colleagues from the Aging Research Center and Department of Clinical Neuroscience, Karolinska Institutet & Stockholm University, Stockholm, Sweden reported their study on the role of childhood school performance, education and the complexity of a person's job on the risk of dementia. The investigators used data from 440 men and women age 75 and older who started the study with good cognitive functioning in the Kungsholmen project, a multifaceted research program to gather information about aging and dementia.

163 people (37%) developed dementia during a nine-year follow up period. The results were cross-referenced with school grades in five elementary school subjects (mathematics, reading, geography, history, and writing) from when the participants were nine or 10 years old. The researchers also had collected information on the participants' formal education and occupational complexity.

The researchers found several significant correlations between grades and dementia risk:

• Dementia risk was elevated more than 50% in individuals over 75 with the lowest 20% of early-life school grades, even if they had more formal education or a job requiring significant complexity.
• Individuals who completed secondary education had a lower risk of dementia compared to individuals with only elementary education (28% lower risk).
• Women in the study who had an occupation with high complexity with people (e.g., high demands on negotiating, instructing, and supervising) were at 60% lower risk of developing dementia compared to those who had an occupation with low complexity with people.

"These findings suggest that early-life cognitive ability may be an important predictor of dementia in late life," said Wang.