rate of decline

Depression linked to faster cognitive decline in older adults

  • A review of 34 studies confirms depression is linked to faster cognitive decline in older adults.

A review of 34 longitudinal studies, involving 71,244 older adults, has concluded that depression is associated with greater cognitive decline.

The study included people who presented with symptoms of depression as well as those that were diagnosed as clinically depressed, but excluded any who were diagnosed with dementia at the start of study.

Previous research has found that depression is associated with an increased dementia risk.

The researchers recommend that preventative measures such as exercising, practicing mindfulness, and undertaking recommended therapeutic treatments, such as Cognitive Behaviour Therapy, might help protect cognitive health.

While the review included some studies into anxiety, the numbers were insufficient to draw a conclusion.

https://www.eurekalert.org/pub_releases/2018-05/uos-dsu052318.php

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Stroke speeds age-related cognitive decline

  • A large study shows stroke is associated not only with an immediate drop in cognitive ability, but also with faster declines in some cognitive functions.
  • The finding points to a need for better long-term care.

Data from 23,572 Americans from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study has revealed that those who survived a stroke went on to have significantly faster rates of cognitive decline as they aged.

Participants, who were aged 45 years or older, had no history of cognitive impairment at the beginning of the population-based study. Over the next five to seven years, 515 of them (2%) had a stroke.

Stroke was associated with an acute decline in global cognition, new learning, and verbal memory. Those who had a stroke showed faster declines in global cognition and executive function (but not new learning nor verbal memory) over the next years.

Global cognition was assessed using the Six-Item Screener [SIS]; new learning by the Consortium to Establish a Registry for Alzheimer Disease Word-List Learning; verbal memory by the Word-List Delayed Recall; executive function by the Animal Fluency Test.

The findings suggest a need for better long-term follow-up care for stroke survivors, including therapy to retain or even regain cognitive ability.

http://www.eurekalert.org/pub_releases/2015-07/uomh-mt070715.php

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Low vitamin D speeds age-related cognitive decline

  • On average, older adults with low levels of vitamin D showed much faster decline in episodic memory and executive function.
  • Older adults with dementia had significantly lower levels of vitamin D compared to those with MCI or normal cognition.
  • Low vitamin D was more common in African-Americans and Hispanics, compared to whites.

A study involving 382 older adults (average age 75) followed for around five years, has found that those who don’t get enough vitamin D may experience cognitive decline at a much faster rate than people who have adequate vitamin D.

Participants included 17.5% with dementia at the beginning of the study, 32.7% with MCI, and 49.5% cognitively healthy.

Those with dementia had lower levels of vitamin D than the other two groups.

While some people with low vitamin D didn’t show any cognitive decline and some with adequate vitamin D declined quickly, people with low vitamin D on average declined two to three times as fast as those with adequate vitamin D, in two crucial cognitive domains: episodic memory and executive function. Semantic memory and visuospatial ability were not significantly affected.

Factors such as age, gender, education, BMI, season of blood draw, vascular risk, and presence of the 'Alzheimer's gene', ApoE4, were controlled for.

Unlike previous studies of vitamin D and dementia, the participants were racially and ethnically diverse and included whites (41%), African Americans (30%), and Hispanics (25%). Nearly two-thirds (61%) had low vitamin D levels in their blood, including 54% of the whites and 70% of the African-Americans and Hispanics.

Vitamin D is primarily obtained through sun exposure. Accordingly, people with darker skin are more likely to have low levels of vitamin D because melanin blocks ultra-violet rays.

It remains to be seen whether Vitamin D supplements could slow cognitive decline.

http://www.futurity.org/vitamin-d-cognitive-decline-1003932/

 

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Early surgical menopause linked to faster cognitive decline

February, 2013

Women who undergo surgical menopause at an earlier age may have an increased risk of cognitive decline.

The issue of the effect of menopause on women’s cognition, and whether hormone therapy helps older women fight cognitive decline and dementia, has been a murky one. Increasing evidence suggests that the timing and type of therapy is critical. A new study makes clear that we also need to distinguish between women who experience early surgical menopause and those who experience natural menopause.

The study involved 1,837 women (aged 53-100), of whom 33% had undergone surgical menopause (removal of both ovaries before natural menopause). For these women, earlier age of the procedure was associated with a faster decline in semantic and episodic memory, as well as overall cognition. The results stayed the same after factors such as age, education and smoking were taken into consideration.

There was also a significant association between age at surgical menopause and the plaques characteristic of Alzheimer's disease. However, there was no significant association with Alzheimer’s itself.

On the positive side, hormone replacement therapy was found to help protect those who had surgical menopause, with duration of therapy linked to a significantly slower decline in overall cognition.

Also positively, age at natural menopause was not found to be associated with rate of cognitive decline.

Reference: 

Bove, R. et al. 2013. Early Surgical Menopause Is Associated with a Spectrum of Cognitive Decline. To be presented at the American Academy of Neurology's 65th Annual Meeting in San Diego, March 21, 2013.

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Hearing loss accelerates cognitive decline in older adults

February, 2013

A large study finds that hearing loss significantly increases the rate of cognitive decline in old age.

I’ve written before about the gathering evidence that sensory impairment, visual impairment and hearing loss in particular, is a risk factor for age-related cognitive decline and dementia. Now a large long-running study provides more support for the association between hearing loss and age-related cognitive decline.

The study involved 1,984 older adults (aged 75-84) whose hearing and cognition was tested at the start of the study, with cognitive performance again assessed three, five, and six years later.

Those with hearing loss showed significantly faster cognitive decline than those with normal hearing — some 30-40% faster (41% on the MMSE; 32% on the Digit Symbol Substitution Test), with rate directly related to the amount of hearing loss.

On average, older adults with hearing loss developed significant cognitive impairment 3.2 years sooner than those with normal hearing — a very significant difference indeed.

It has been suggested that increasing social isolation and loneliness may underlie some, if not all, of this association. It may also be that difficulties in hearing force the brain to devote too much of its resources to processing sound, leaving less for cognition. A third possibility is that some common factor underlies both hearing loss and cognitive decline — however, the obvious risk factors, such as high blood pressure, diabetes and stroke, were taken account of in the analysis.

The findings emphasize the importance of getting help for hearing difficulties, rather than regarding them as ‘natural’ in old age.

Reference: 

[3293] Lin, F. R., Yaffe K., Xia J., & et al
(2013).  Hearing loss and cognitive decline in older adults.
JAMA Internal Medicine. 1 - 7.

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Why metabolic syndrome is linked to cognitive decline?

October, 2012

Preliminary results for a small study indicate metabolic syndrome is linked to significantly reduced blood flow in the brain, perhaps explaining its link to cognitive impairment.

I’ve reported before on the growing evidence that metabolic syndrome in middle and old age is linked to greater risk of cognitive impairment in old age and faster decline. A new study shows at least part of the reason.

The study involved 71 middle-aged people recruited from the Wisconsin Registry for Alzheimer's Prevention (WRAP), of whom 29 met the criteria for metabolic syndrome (multiple cardiovascular and diabetes risk factors including abdominal obesity, high blood pressure, high blood sugar and high cholesterol).

Those with metabolic syndrome averaged 15% less blood flow to the brain than those without the syndrome.

One tried and true method of increasing blood flow to the brain is of course through exercise.

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The study was presented at the Alzheimer's Association International Conference in Vancouver, Canada by Barbara Bendlin.

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Controlling diabetes important for slowing cognitive decline

August, 2012
  • Findings from a large, long-running study adds to growing evidence that poorly controlled diabetes is associated with faster cognitive decline.

The latest finding from the large, long-running Health, Aging, and Body Composition (Health ABC) Study adds to the evidence that preventing or controlling diabetes helps prevent age-related cognitive decline.

The study involves 3,069 older adults (70+), of whom 717 (23%) had diabetes at the beginning of the study in 1997. Over the course of the study, a further 159 developed diabetes. Those with diabetes at the beginning had lower cognitive scores, and showed faster decline. Those who developed diabetes showed a rate of decline that was between that faster rate and the slower rate of those who never developed diabetes.

Among those with diabetes, those who had higher levels of a blood marker called glycosylated hemoglobin had greater cognitive impairment. Higher levels of this blood marker reflect poorer control of blood sugar.

In other words, both duration and severity of diabetes are important factors in determining rate of cognitive decline in old age.

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Air pollution linked to age-related cognitive decline

April, 2012

A large long-running study of older women has found a dose-dependent association between air pollution and cognitive decline. A review has found a dose-dependent association between air pollution and risk of heart attack.

Data from the Nurses' Health Study Cognitive Cohort, involving 19,409 older women (70-81), has found that higher levels of long-term exposure to air pollution were associated with faster rates of cognitive decline over a four-year period.

For each 10 micrograms per cubic meter of air increase in pollutants, cognitive decline was comparable to two years of age-related decline.

Pollution exposure was estimated from geography. Cognition was tested by three telephone interviews, administered at roughly two-year intervals.

Air pollution linked to heart attack risk

Given the association between cardiovascular risk factors and cognitive decline (“What’s good for the heart is good for the brain”), it’s worth noting that a review of 34 studies has found that every main air pollutant, with the exception of ozone, was significantly associated with greater risk of heart attack. For most of the pollutants, an increase in concentration of 10 micrograms per cubic meter of air – barely noticeable – was associated with a 1-3% increase in the chance of having a heart attack in the next week.

The size of the risk is small compared with traditional risk factors such as smoking status or hypertension or diabetes, but is something that those with other cardiovascular risk factors may want to consider. There’s also growing evidence that high levels of pollution increase stroke risk.

For more about the effects of air pollution on cognition

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Severe, rapid memory loss linked to future, fatal strokes

March, 2012

A large, long-running study has revealed that older adults who suffered a fatal stroke showed significantly faster cognitive decline in the years preceding the stroke compared to stroke survivors and stroke-free adults.

A ten-year study following 12,412 middle-aged and older adults (50+) has found that those who died after stroke had more severe memory loss in the years before stroke compared to those who survived stroke and those who didn't have a stroke.

Participants were tested every two years, using a standard word-recall list to measure memory loss (or caregiver assessment for those whose memory loss was too severe). During the decade of the study, 1,027 participants (8.3%) survived a stroke, 499 (4%) died after stroke, and 10,886 (87.7%) remained stroke-free over the study period.

Before having a stroke, those who later survived a stroke had worse average memory than similar individuals who never had a stroke, however their rate of memory decline was similar (0.034 and 0.028 points per year, respectively). Those who later died after a stroke, on the other hand, showed significantly faster memory decline (0.118 points per year).

Whether this is because those who die after stroke have a more compromised brain prior to the stroke, or because greater memory impairment makes people more vulnerable in the wake of a stroke, cannot be told from this data (and indeed, both factors may be involved).

Among survivors, stroke had a significant effect on memory decline, with memory scores dropping an average of 0.157 points at the time of the stroke — an amount equivalent to around 5.6 years of memory decline in similarly-aged stroke-free adults. However, in subsequent years, decline was only a little greater than it had been prior to the stroke (0.038 points per year).

(You can see a nice graph of these points here.)

Reference: 

Wang, Q., Capistrant, B.D., Ehntholt, A. & Glymour, M.M. 2012. Abstract 31: Rate of Change in Memory Functioning Before and After Stroke Onset. Presented at the American Stroke Association's International Stroke Conference 2012. http://stroke.ahajournals.org/cgi/content/meeting_abstract/43/2_MeetingAbstracts/A31?sid=960f2015-06d1-478f-8c03-c00994d35f2c

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Memory loss in old age the price we pay for a large brain & a long life?

September, 2011

Chimpanzee brains don’t shrink with age as humans’ do. It may be that cognitive impairment and even dementia are our lot because we work our brains too hard for too long.

Comparison of 99 chimpanzee brains ranging from 10-51 years of age with 87 human brains ranging from 22-88 years of age has revealed that, unlike the humans, chimpanzee brains showed no sign of shrinkage with age. But the answer may be simple: we live much longer. In the wild, chimps rarely live past 45, and although human brains start shrinking as early as 25 (as soon as they reach maturity, basically!), it doesn’t become significant until around 50.

The answer suggests one reason why humans are uniquely vulnerable to Alzheimer’s disease — it’s all down to our combination of large brain and long life. There are other animals that experience some cognitive impairment and brain atrophy as they age, but nothing as extreme as that found in humans (a 10-15% decline in volume over the life-span). (Elephants and whales have the same two attributes as humans — large brains and long lives — but we lack information on how their brains change with age.)

The problem may lie in the fact that our brains use so much more energy than chimps’ (being more than three times larger than theirs) and thus produce a great deal more damaging oxidation. Over a longer life-span, this accumulates until it significantly damages the brain.

If that’s true, it reinforces the value of a diet high in antioxidants.

Reference: 

[2500] Sherwood, C. C., Gordon A. D., Allen J. S., Phillips K. A., Erwin J. M., Hof P. R., et al.
(2011).  Aging of the cerebral cortex differs between humans and chimpanzees.
Proceedings of the National Academy of Sciences. 108(32), 13029 - 13034.

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