Wednesday, August 26, 2015

Nine risk factors for Alzheimer's

Reprinted from a newsletter called:

Aging and Parkinson's and Me

Aging and Parkinson's and Me

Posted: 25 Aug 2015 08:57 AM PDT
An article published online last week in the Journal of Neurology, Neurosurgery & Psychiatry describes nine risk factors for Alzheimer's disease (AD). The data from this study suggests that these nine factors contribute to two thirds of all AD cases worldwide.

What's more, these remarkably varied risk factors are all modifiable; there is something we can do about them. That's important because there is no cure for the disease that affects over 44 million people around the world… and hundreds of millions of family members and caregivers.

Eager to study the complexity of AD development, researchers in China and California undertook a monumental enterprise: reviewing all relevant studies published in English from 1968 to July, 2014 (in PubMed and the Cochrane Database of Systematic Reviews).

From the 16,906 studies they reviewed, the scientists identified 323 that offered data they could include in their own study. From those 323 studies, the team found 93 separate possible AD risk factors that involved more than 5,000 people.

Because they were especially concerned with the causes – the complexity – of dementia development, the researchers pooled the metadata from all the applicable studies and evaluated the evidence based on its strength.

First, the Evidence
The team found "grade 1 level evidence" (evidence obtained from at least one properly designed randomized controlled trial) that the following medical exposures were protective against dementia development: 
  • The female hormone estrogen
  • Statins (cholesterol-lowering drugs)
  • Drugs to lower high blood pressure
  • NSAIDS (non-steroidal anti-inflammatory drugs)
The scientists found the same quality of evidence – protective against AD – for these dietary exposures:
  • Folate (a water-soluble B vitamin naturally present in some foods, added to others, and available as a dietary supplement)
  • Vitamins C and E
  • Coffee

On the other hand, the scientists found a strong association between the following and a heightened risk of developing AD:

  • A biochemical exposure -- high levels of homocysteine (an amino acid manufactured in the body)
  • A psychological condition -- depression

There was strong evidence – one way or another -- of the impact of pre-existing conditions. These histories lowered dementia development risk:
  • Arthritis
  • Heart disease
  • Metabolic syndrome
  • Cancer

These pre-existing conditions created increased risk:
  • Frailty
  • Carotid artery narrowing
  • Hypertension
  • Low diastolic (bottom number) blood pressure 
  • Type 2 diabetes (in the Asian population)

Other lifestyle factors came to bear on dementia risk. First, those that seemed to lower AD risk:
  • High BMI (body mass index) in late life
  • Cognitive activity
  • Current smoking (Western population)
  • Light-to-moderate drinking
  • Stress

And these factors heightened dementia risk:
  • High BMI in mid-life, and low BMI generally
  • Low educational attainment

Researchers found no AD associations one way or the other for workplace factors.

The scientists had an enormous amount of data in the pot. They rigorously evaluated it, making sure their results reflected global prevalence. Once they identified potential risk factors, they assessed the "population attributable risk" (PAR) for those factors, using a complex mathematical formula that – among other things – defined the degree of disease that would disappear if exposure to specific risk factors were eliminated.

Finally, the Nine Risk Factors
After that rigorous scrutiny, here are the risk factors that made the cut:
  • Obesity
  • Current smoking (in the Asian population)
  • Carotid artery narrowing
  • Type 2 diabetes
  • Low educational attainment
  • High homocysteine levels
  • Drepression
  • High blood pressure
  • Frailty
As so often happens, this study – comprehensive as it seems – is observational only. We can draw no definitive conclusions about cause and effect.

Still, there's a major upside to this information: these factors are "modifiable." We can mitigate these risks with effective interventions in diet, medications, biochemical exposures, psychological condition, pre-existing disease and lifestyle.

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