rate of decline

Smaller life space linked to greater risk of cognitive decline

June, 2011

A study of healthy seniors reveals that homebodies have faster cognitive decline and more risk of developing Alzheimer’s and MCI, than those who have a wider life-space.

Growing evidence has pointed to the benefits of social and mental stimulation in preventing dementia, but until now no one has looked at the role of physical environment.

A study involving 1294 healthy older adults found that those whose life-space narrowed to their immediate home were almost twice as likely to develop the condition as those with the largest life-space (out-of-town). The homebound also had an increased risk of MCI and a faster rate of global cognitive decline.

By the end of the eight-year study (average follow-up of 4.4 years), 180 people (13.9%) had developed Alzheimer’s. The association remained after physical function, disability, depressive symptoms, social network size, vascular disease burden, and vascular risk factors, were taken into account.

It may be that life-space is an indicator of how engaged we are with the world, with the associated cognitive stimulation that offers.

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Protein in the urine: A warning sign for cognitive decline

December, 2010

Two recent studies indicate that the presence of protein in the urine, even in small amounts, could be a warning sign that a patient may develop cognitive impairment with age.

A six-year study involving over 1200 older women (70+) has found that low amounts of albumin in the urine, at levels not traditionally considered clinically significant, strongly predict faster cognitive decline in older women. Participants with a urinary albumin-to-creatinine ratio of >5 mcg/mg at the start of the study experienced cognitive decline at a rate 2 to 7 times faster in all cognitive measures than that attributed to aging alone over an average 6 years of follow-up. The ability most affected was verbal fluency. Albuminuria may be an early marker of diffuse vascular disease.

Data from 19,399 individuals participating in the Renal Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, of whom 1,184 (6.1%) developed cognitive impairment over an average follow-up of 3.8 years, has found that those with albuminuria were 1.31-1.57 times more likely to develop cognitive impairment compared to individuals without albuminuria. This association was strongest for individuals with normal kidney function. Conversely, low kidney function was associated with a higher risk for developing cognitive impairment only among individuals without albuminuria. Surprisingly, individuals with albuminuria and normal kidney function had a higher probability for developing cognitive impairment as compared to individuals with moderate reductions in kidney function in the absence of albuminuria.

Both albuminuria and low kidney function are characteristics of kidney disease.

Reference: 

Lin, J., Grodstein, F., Kang, J.H. & Curhan, G. 2010. A Prospective Study of Albuminuria and Cognitive Decline in Women. Presented at ASN Renal Week 2010 on November 20 in Denver, CO.

Tamura, M.K. et al. 2010. Albuminuria, Kidney Function and the Incidence of Cognitive Impairment in US Adults. Presented at ASN Renal Week 2010 on November 20 in Denver, CO.

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Vascular disease underlies cognitive decline in healthy aging

December, 2010
  • New findings add to evidence that the key to not becoming cognitively impaired in old age is vascular health.

More evidence that vascular disease plays a crucial role in age-related cognitive impairment and Alzheimer’s comes from data from participants in the Alzheimer's Disease Neuroimaging Initiative.

The study involved more than 800 older adults (55-90), including around 200 cognitively normal individuals, around 400 people with mild cognitive impairment, and 200 people with Alzheimer's disease. The first two groups were followed for 3 years, and the Alzheimer’s patients for two. The study found that the extent of white matter hyperintensities (areas of damaged brain tissue typically caused by cardiovascular disease) was an important predictor of cognitive decline.

Participants whose white matter hyperintensities were significantly above average at the beginning of the study lost more points each year in cognitive testing than those whose white matter hyperintensities were average at baseline. Those with mild cognitive impairment or Alzheimer's disease at baseline had additional declines on their cognitive testing each year, meaning that the presence of white matter hyperintensities and MCI or Alzheimer's disease together added up to even faster and steeper cognitive decline.

The crucial point is that this was happening in the absence of major cardiovascular events such as heart attacks, indicating that it’s not enough to just reduce your cardiovascular risk factors to a moderate level — every little bit of vascular damage counts.

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Mental activity may slow cognitive decline initially, but speed up dementia later

October, 2010

Another study has come out suggesting that the advantage of mental stimulation is to delay cognitive decline, but at the cost of faster decline later (it’s still a good bargain).

A long-running study involving 1,157 healthy older adults (65+) who were scored on a 5-point scale according to how often they participated in mental activities such as listening to the radio, watching television, reading, playing games and going to a museum, has found that this score is correlated to the rate of cognitive decline in later years.

Some 5 ½ years after this initial evaluation, 395 (34%) were found to have mild cognitive impairment and 148 (13%) to have Alzheimer’s. Participants were then tested at 3-yearly intervals for the next 6 years. The rate of cognitive decline in those without cognitive impairment was reduced by 52% for each point on the cognitive activity scale, but for those with Alzheimer's disease, the average rate of decline per year increased by 42% for each point on the cognitive activity scale. Rate of decline was unrelated to earlier cognitive activity in those with MCI (presumably they were at the balance point).

This is not terribly surprising when you think of it, if you assume that the benefit of mental stimulation is to improve your brain function so that it can better cope with the damage happening to it. But eventually it reaches the point where it can no longer compensate for that damage because it is so overwhelming.

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New advice on how much cognitive abilities decline with age

October, 2010

A new study suggests that inconsistencies in rate of age-related cognitive decline may be partly due to practice effects, but though decline does occur it is slower than some have estimated.

Reports on cognitive decline with age have, over the years, come out with two general findings: older adults do significantly worse than younger adults; older adults are just as good as younger adults. Part of the problem is that there are two different approaches to studying this, each with their own specific bias. You can keep testing the same group of people as they get older — the problem with this is that they get more and more practiced, which mitigates the effects of age. Or you can test different groups of people, comparing older with younger — but cohort differences (e.g., educational background) may disadvantage the older generations. There is also argument about when it starts. Some studies suggest we start declining in our 20s, others in our 60s.

One of my favorite cognitive aging researchers has now tried to find the true story using data from the Virginia Cognitive Aging Project involving nearly 3800 adults aged 18 to 97 tested on reasoning, spatial visualization, episodic memory, perceptual speed and vocabulary, with 1616 tested at least twice. This gave a nice pool for both cross-sectional and longitudinal comparison (retesting ranged from 1 to 8 years and averaged 2.5 years).

From this data, Salthouse has estimated the size of practice effects and found them to be as large as or larger than the annual cross-sectional differences, although they varied depending on the task and the participant’s age. In general the practice effect was greater for younger adults, possibly because younger people learn better.

Once the practice-related "bonus points" were removed, age trends were flattened, with much less positive changes occurring at younger ages, and slightly less negative changes occurring at older ages. This suggests that change in cognitive ability over an adult lifetime (ignoring the effects of experience) is smaller than we thought.

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Subjective memory loss may increase risk for MCI & dementia

January, 2010

Healthy older adults reporting subjective cognitive impairment are dramatically more likely to progress to MCI or dementia, and decline significantly faster.

Subjective cognitive impairment (SCI), marked by situations such as when a person recognizes they can't remember a name like they used to or where they recently placed important objects the way they used to, is experienced by between one-quarter and one-half of the population over the age of 65. A seven-year study involving 213 adults (mean age 67) has found that healthy older adults reporting SCI are dramatically more likely to progress to MCI or dementia than those free of SCI (54% vs 15%). Moreover, those who had SCI declined significantly faster.

Reference: 

Reisberg, B. et al. 2010. Outcome over seven years of healthy adults with and without subjective cognitive impairment. Alzheimer's & Dementia, 6 (1), 11-24.

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The age you feel is more important for cognition than the age you are

February, 2010

More data from the National Survey of Midlife Development in the United States has revealed that cognitive abilities reflect to a greater extent how old you feel, not how old you actually are.

More data from the National Survey of Midlife Development in the United States has revealed that cognitive abilities reflect to a greater extent how old you feel, not how old you actually are. Of course that may be because cognitive ability contributes to a person’s wellness and energy. But it also may reflect benefits of trying to maintain a sense of youthfulness by keeping up with new trends and activities that feel invigorating.

Reference: 

[171] Schafer, M. H., & Shippee T. P.
(2009).  Age Identity, Gender, and Perceptions of Decline: Does Feeling Older Lead to Pessimistic Dispositions About Cognitive Aging?.
The Journals of Gerontology Series B: Psychological Sciences and Social Sciences. 65B(1), 91 - 96.

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Personality may influence brain shrinkage in aging

March, 2010
  • An imaging study involving 79 volunteers aged 44 to 88 has found more brain atrophy and faster rates of decline in brain regions particularly affected by aging, among those ranked high in neuroticism traits.

An imaging study involving 79 volunteers aged 44 to 88 has found lower volumes of gray matter and faster rates of decline in the frontal and medial temporal lobes of those who ranked high in neuroticism traits, compared with those who ranked high in conscientious traits. These are brain regions particularly affected by aging. The idea that this might occur derived from the well-established effects of chronic stress on the brain. This is the first study to investigate whether the rate and extent of cognitive decline with age is influenced by personality variables. Extraversion, also investigated, had no effect. The study does not, however, rule out the possibility that it is reduction in brain tissue in these areas that is affecting personality. There is increasing evidence that people tend to become more neurotic and less conscientious in early-stage Alzheimer's.

Reference: 

[174] Jackson, J., Balota D. A., & Head D.
(Submitted).  Exploring the relationship between personality and regional brain volume in healthy aging.
Neurobiology of Aging. In Press, Corrected Proof,

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