Monday, February 06, 2017

Study Finding It Isn't Concludes Eating Grapes Beneficial to Alzheimer's Care

I'm a gadget guy, and I regularly read a tech blog called New Atlas. Their coverage is wide-ranging, and it isn't just gadgets they cover but science-y topics as a whole.

The other day an article caught my eye. The headline read,
"Two cups of grapes a day may keep the Alzheimer's away".
Reading the piece I learned that,
"a recent study conducted by the University of California, Los Angeles indicates that consuming them (grapes) helps protect against Alzheimer's disease",
and that,
"This pilot study contributes to the growing evidence that supports a beneficial role for grapes in neurologic and cardiovascular health".
But there were some giant red flags.
  • The study involved just 10 people.
  • The study did not involve eating actual grapes.
  • The coverage did not mention whether or not those 5 people consuming freeze-dried grape powder performed differently on the battery of cognitive tests administered to them before and after the 6 month intervention.
  • The coverage credited a press release from The California Table Grape Commission as its source.
So I decided to read the study itself.

Reading it, along with its study record detail, I learned that the study was designed to determine the degree of cognitive benefit associated with the consumption of freeze dried grape powder as well as whether benefits correlated with neuro-imaging changes in the participants

The cognitive testing sure was thorough, and given there were only 5 participants in the intervention arm and 24 tests administered, the chances of one coming back with a between groups difference even just by chance was much higher. Researchers administered the following tests:
  1. Cognitive subscale/ADAS-Cog (Rosen et al., 1984)
  2. Mini-mental Status Exam/MMSE (Folstein et al., 1975)
  3. Hopkins Verbal Learning Test-Revised (Benedict et al., 1998)
  4. Benton Visual Retention Test (Benton, 1955)
  5. Rey-Osterreith Complex Figure Test delayed (Osterrieth, 1944)
  6. Boston Naming Test (Kaplan et al., 1983)
  7. Letter Fluency FAC (Strauss and Spreen, 1998)
  8. Animal naming (Goodglass et al., 1972)
  9. Stroop Interference (Golden, 1978)
  10. Trail Making Test-Part B (Reitan, 1958)
  11. Wisconsin Card Sorting Test-64 (Heaton, 1981)
  12. Speed of information processing (Trail Making Test Part A (20)
  13. WAIS-III Digital Symbol (Wechsler, 1997)
  14. WAIS-III Symbol speed (Wechsler, 1997)
  15. Complex figure test copy (Osterrieth, 1944)
  16. WAIS-III Block Design (Wechsler, 1997)
  17. WAIS-III Symbol search total (Wechsler, 1997)
  18. WAIS-III Letter-Number Sequencing (Wechsler, 1997)
  19. WAIS-III Digital Span (Wechsler, 1997)
  20. Wechsler Test of Adult Reading (Wechsler, 2001),
  21. Memory Functioning Questionnaire (Gilewski et al., 1990)
  22. Hamilton Depression Rating Scale (Hamilton, 1960)
  23. Hamilton Anxiety Rating Scale (Hamilton, 1959)
  24. The Clinician's Interview Based Impression of Change (Knopman et al., 1994)
As for the results? Even with that barrage of tests,
"No significant benefits for the active formulation arm were noted in scores on the assessments in the neuropsychological battery"
Amazingly, despite registering their trial with the stated primary outcome measure of,
"Change from baseline in neuropsychological (cognitive, functional) test results",
the authors describe their null results as being,
"not unexpected given the small sample sizes relative to large inter-individual variation on such tests."
Perhaps the most striking piece for me though was in the authors' conclusion about their study that involved the consumption of freeze-dried grape powder and demonstrated no clinical benefit despite throwing literally two dozen tests at the subjects,
"In conclusion, twice-daily consumption of table grapes was associated with significant protection from longitudinal changes in cerebral metabolism, which in turn were correlated with improvement in attention/working memory performances, consistent with a beneficial effect of daily intake of grapes with respect to preservation of metabolic activity in individuals experiencing mild cognitive decline."
Imagine my non-surprise when I came across the next line:

While I completely understand why authors funded by the California Table Grape Commission might want to make their study sound more exciting than its results would warrant, I have more difficulty understanding why journalists would choose to report on it non-critically? I mean if you're going to write a piece about it, isn't the bigger story the spin? Yesterday I asked the journalist who wrote the New Atlas piece on Twitter what made him want to cover it. Unfortunately I didn't hear back.

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