Childhood School Performance And Type 1 Diabetes Identified As Risk Factors For Alzheimer's Disease, Dementia

Loneliness and High TV Viewing also Linked to Lower Cognitive Function, According to Reports from the Alzheimer's Association International Conference 2015

Jul 20, 2015, 08:00 ET from Alzheimer's Association

WASHINGTON, July 20, 2015 /PRNewswire-USNewswire/ -- The first study of dementia risk, including Alzheimer's disease, in older adults with type 1 diabetes (T1D) was reported today at the Alzheimer's Association International Conference® 2015 (AAIC® 2015) in Washington, D.C. People in the study with T1D were 93% more likely to get dementia (73% after adjustment for heart health risk factors) compared with people without diabetes.

Two studies presented at AAIC 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."

Given the growing evidence that people can reduce their risk of cognitive decline, the Alzheimer's Association recently shared 10 Ways to Love Your Brain, tips that may help lessen the chance of cognitive decline as we age. The suggestions include engaging in regular cardiovascular exercise that elevates your heart rate, getting more formal education, and quitting smoking. The complete list can be found at alz.org.

First Study of Type 1 Diabetes and Risk of Dementia in Late Life

Type 1 diabetes (T1D) is a chronic condition where the pancreas produces little or no insulin, which is a hormone that regulates the movement of sugar into your cells. It is usually diagnosed in children and young adults. In type 2 diabetes (T2D), the body either resists the effects of insulin or doesn't produce enough insulin to maintain a normal glucose level. It is more common in adults, and is the most common form of diabetes, affecting 90 to 95% of Americans with diabetes.

Studies have shown that T2D is associated with a greater risk of dementia, including Alzheimer's disease; however, little is known about how T1D affects cognitive aging and dementia risk. At AAIC 2015, Rachel Whitmer, PhD, Kaiser Permanente Division of Research, Oakland CA, and colleagues reported results from first study of dementia in elderly adults with T1D.

"Elderly people with type 1 diabetes are a population that is unique from elderly people with type 2 diabetes," Whitmer said. "They have a much younger age of diabetes onset, continuous insulin treatment, more frequent severe hypoglycemic episodes, but less vascular risk factors."

The researchers followed the health histories of 490,344 people over 60 years old with no prior dementia who are in the Kaiser Permanente Northern California health system, tracking them over 12 years for new dementia diagnoses. 334 individuals had T1D. Analyses compared the T1D group with two control groups: one with T2D and one without diabetes, taking into account differences in gender, race, stroke, peripheral arterial disease and hypertension.

Results presented at AAIC 2015 show that 16% of those with T1D in the study were diagnosed with dementia during the follow-up period while 12% of those without T1D developed dementia.  In other words, people in the study with T1D were 83% more likely to get dementia compared with people who did not have T1D; 61% more likely after adjustment for stroke, peripheral arterial disease and hypertension. The magnitude of T1D on dementia risk was larger when people with T2D were excluded for the comparison group (93% more likely; 73% after adjustment).

"Both type 1 and type 2 diabetes are rapidly increasing worldwide, and people with type 1 are living longer than ever before," Whitmer said. "Since management of type 1 diabetes requires vigilance and constant self-care, cognitive impairment poses a particular threat to this vulnerable population. More research is needed to identify risk and protective factors for Alzheimer's and other dementias in this group that is newly entering the aging population."

How School Grades, Formal Education, and Work Complexity Impact Dementia Risk

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. (See the next description.)

School Performance, Education and Occupational Complexity: Corroboration

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.

Low Physical Activity and High TV Viewing are Associated with Worse Cognitive Function

Physical activity in later life is generally considered a protective factor against cognitive decline and possibly Alzheimer's and other dementias, but little is known about the role of physical activity in early adulthood.

"Understanding this relationship in early adulthood may be particularly important because global data suggests that levels of physical inactivity and sedentary behavior are increasing," said Tina Hoang, MSPH, of the Northern California Institute of Research and Education (NCIRE), San Francisco, with her mentor, Kristine Yaffe, MD, of the University of California, San Francisco.

Yaffe, Hoang and colleagues investigated the association of long-term patterns of low physical activity and high television viewing time over 25 years with cognitive function at mid-life. The study population included more than 3,200 black and white adults, 18-30 years old, in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Physical activity and television viewing were assessed at repeated visits (≥3 assessments) over 25 years. Low physical activity was defined as activity below 300 kcal/50 min session, 3 times per week; high television viewing was defined as more than 4 hours per day.

A long-term pattern of each behavior was defined as meeting these cutoffs for more than two-thirds of visits. 17% of participants reported a long-term pattern of low physical activity, 11% a long-term pattern of high television viewing, and 3% reported both. At year 25 of the study, participants were assessed for memory, executive function and processing speed using well-established tests.

At AAIC 2015, Yaffe, Hoang and colleagues reported that study participants with low levels of physical activity over 25 years had significantly worse cognition in mid-life, adjusting for age, race, sex, education, smoking, alcohol, BMI, and hypertension. Similarly, participants with high levels of TV watching over 25 years also had significantly worse mid-life cognitive function. Study participants with both long-term low physical activity and high television viewing were almost two times more likely to have poor cognitive function in mid-life.

"Our findings demonstrate that even early- and mid-adulthood may be critical periods for promotion of physical activity for healthy cognitive aging," Hoang said. "Sedentary behaviors, like TV viewing, could be especially relevant for future generations of adults due to the growing use of screen-based technologies. Because research indicates that Alzheimer's and other dementias develop over several decades, increasing physical activity and reducing sedentary behavior beginning in early adulthood may have a significant public health impact."

Loneliness is Associated with Worse Cognitive Function in a Study of Older U.S. Adults

Research suggests that late-life depression is associated with future incidence of Alzheimer's in some older adults. In general, less is known about individual aspects of, or causative factors for, depression and their relationship to Alzheimer's/dementia risk. One component, loneliness, has been associated with functional decline and increased progression to dementia.

To examine the relationship between loneliness and cognitive function in older adults, Nancy J. Donovan, MD, Brigham and Women's Hospital and Harvard Medical School, Boston, MA, and colleagues examined data from more than 8,300 adults age 65 and older participating in the U.S. Health and Retirement Study from 1998 to 2010. Participants in that study had assessments of their loneliness, depression, cognitive function and memory, health status, and social network characteristics every two years. Seventeen percent (17%) of participants reported loneliness at the beginning of the study with approximately half of the lonely individuals reporting clinically significant depression.

At AAIC 2015, the researchers reported that the loneliest people in the study experienced accelerated cognitive decline – approximately 20% faster over 12 years – than people who were not lonely, regardless of demographic factors, social network, health conditions and baseline depression. Similarly, people reporting depression at baseline experienced significantly faster cognitive decline during the study. However, looking in the other direction, the researchers found lower cognitive function does not lead to worsening loneliness.

"Our study suggests that even one or two depressive symptoms – particularly loneliness – is associated with an increased rate of cognitive decline over 12 years," Donovan said. "We found that lonely people decline cognitively at a faster rate than people who report more satisfying social networks and connections. Although loneliness and depression appear closely linked, loneliness may, by itself, have effects on cognitive decline. This is important to know as we develop treatments to enhance cognitive health and quality of life for older adults."

About AAIC

The Alzheimer's Association International Conference (AAIC) is the world's largest gathering of leading researchers from around the world focused on Alzheimer's and other dementias. As a part of the Alzheimer's Association's research program, AAIC serves as a catalyst for generating new knowledge about dementia and fostering a vital, collegial research community.

AAIC 2015 home page: www.alz.org/aaic/ 
AAIC 2015 newsroom: www.alz.org/aaic/press.asp

About the Alzheimer's Association®

The Alzheimer's Association is the leading voluntary health organization in Alzheimer's care, support and research. Our mission is to eliminate Alzheimer's disease through the advancement of research, to provide and enhance care and support for all affected, and to reduce the risk of dementia through the promotion of brain health. Our vision is a world without Alzheimer's. Visit alz.org or call 800.272.3900.

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