Abstract
Objectives
Neurocognitive function may be influenced by polyunsaturated fat intake. Many older
adults consume omega-3 supplements hoping to prevent cognitive decline. We assessed
effects of increasing omega-3, omega-6, or total polyunsaturated fats on new neurocognitive
illness and cognition.
Design and inclusion criteria
We carried out a systematic review and meta-analysis of randomized controlled trials
(RCTs) in adults, with duration ≥24 weeks, assessing effects of higher vs lower omega-3,
omega-6, or total polyunsaturated fats and outcomes: new neurocognitive illness, newly
impaired cognition, and/or continuous measures of cognition.
Methods
We searched MEDLINE, Embase, Cochrane CENTRAL, and trials registers (final update
of ongoing trials December 2018). We duplicated screening, data extraction, and risk
of bias assessment. Neurocognitive measures were grouped to enable random effects
meta-analysis. GRADE assessment, sensitivity analyses, and subgrouping by dose, duration,
type of intervention, and replacement were used to interrogate our findings.
Results
Searches generated 37,810 hits, from which we included 38 RCTs (41 comparisons, 49,757
participants). Meta-analysis suggested no or very little effect of long-chain omega-3
on new neurocognitive illness [risk ratio (RR) 0.98, 95% confidence interval (CI)
0.87-1.10, 6 RCTs, 33,496 participants, I2 36%), new cognitive impairment (RR 0.99, 95% CI 0.92-1.06, 5 RCTs, 33,296 participants,
I2 0%) or global cognition assessed using the Mini-Mental State Examination (MD 0.10,
95% CI 0.03-0.16, 13 RCTs, 14,851 participants, I2 0%), all moderate-quality evidence. Effects did not differ with sensitivity analyses,
and we found no differential effects by dose, duration, intervention type, or replacement.
Effects of increasing α-linolenic acid, omega-6, or total PUFA were unclear.
Conclusions
This extensive trial data set enabled assessment of effects on neurocognitive illness
and cognitive decline not previously adequately assessed. Long-chain omega-3 probably
has little or no effect on new neurocognitive outcomes or cognitive impairment.
Implications
Long-chain omega-3 supplements do not help older adults protect against cognitive
decline.
Keywords
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Article info
Publication history
Published online: April 15, 2020
Footnotes
This work was supported by the World Health Organization (Grant HQNHD1612458).
Conflicts: J.S.B., O.F.J., K.H.O.D., P.B., A.S.A., and L.H. had financial support via their institution from the World Health Organization for the submitted work, and L.H. and A.S.A. were also funded by WHO to attend WHO meetings and present review results. There were no financial relationships with any organizations that might have an interest in the submitted work in the previous 3 years and no other relationships or activities that could appear to have influenced the submitted work.
Collaborators: The PUFAH (The Polyunsaturated Fats and Health) group also includes Sarah Ajabnoor (Norwich Medical School, University of East Anglia), Faye Alabdulghafoor (Norwich Medical School, University of East Anglia), Lena Alkhudairy (Warwick Medical School, University of Warwick), Charlene Bridges (Cochrane Heart Group, University College London), Sarah Hanson (School of Health Sciences, University of East Anglia), Nicole Martin (Cochrane Heart Group, University College London), Alex O'Brien (Norwich Medical School, University of East Anglia), Karen Rees (Warwick Medical School, University of Warwick), Fujian Song (Norwich Medical School, University of East Anglia), Gabrielle Thorpe (School of Health Sciences, University of East Anglia), Xia Wang (Norwich Medical School, University of East Anglia), and Lauren Winstanley (Norwich Medical School, University of East Anglia).
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