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Supplements of omega-3 fatty acids or other nutrients found in green leafy vegetables do not slow cognitive decline in older people, according to research published in JAMA
[1]
on 25 August 2015.
Researchers measured the cognitive function of 4,000 patients over five years – making it one of the largest and most prolonged studies of its kind.
The results were from a cohort of patients, with an average age of 72 years, who were already enrolled in another study — the Age Related Eye Disease Study (AREDS) — that was tracking their risk of developing late age-related macular degeneration (AMD).
All 4,000 patients were recruited from 82 medical and academic centres in the United States and had either early or intermediate AMD.
The patients were divided into four groups – one group was given a placebo and a second group was given omega-3 long-chain polyunsaturated fatty acids (LCPUFAs), specifically 330mg of docosahexaenoic acid and 650mg of eicosapentaenoic acid. A third group received lutein and zeaxanthin — nutrients commonly found in leafy green vegetables. A fourth group was given omega-3 LCPUFAs and lutein/zeaxanthin.
The patients took part in validated cognitive tests at the beginning of the study and then again at two and four years during the research, which ran from 2006 to 2012.
The researchers found no significant differences in the scores between patients receiving the placebo and those in the three groups receiving supplements.
The yearly change in the composite cognitive function score for patients receiving LCPUFAs was -0.19 compared with -0.18 for those not receiving LCPUFAs. The yearly change in the composite cognitive function score was -0.18 in the group receiving lutein/zeaxanthin compared with -0.19 in patients not receiving the supplement.
“Among older persons with AMD, oral supplementation with LCPUFAs or lutein/zeaxanthin had no statistically significant effect on cognitive function,” say the researchers.
But they queried whether the timing of the nutrients — given over five years as opposed to longer — and the age of the patients may have influenced the results.
The researchers suggest that more studies are needed to discover whether dietary patterns or taking supplements earlier in the development of diseases such as Alzheimer’s would make any difference to their findings.
The trial was published alongside a study[2]
examining the effects of exercise on cognition in older people. The researchers, led by Kaycee Sink, of the Wake Forest School of Medicine in North Carolina, found that a 24-month moderate-intensity physical activity intervention did not result in better cognition among study participants compared with a health education programme designed to encourage healthy aging. And there was no significant difference in the incidence of mild cognitive impairment or dementia between the physical activity and health education groups. However, they did observe improved executive function in older, more vulnerable participants who completed the physical activity programme.
“This finding is important because executive function is the most sensitive cognitive domain to exercise interventions, and preserving it is required for independence in instrumental activities of daily living,” say the researchers.
References
[1] Chew EY, Clemons TE, Agrón E et al. Effect of omega-3 fatty acids, lutein/zeaxanthin, or other nutrient supplementation on cognitive function: the AREDS2 randomized clinical trial. JAMA 2015;314(8):791–801. doi:10.1001/jama.2015.9677.
[2] Sink KM, Espeland MA, Castro CM et al. Effect of a 24-month physical activity intervention vs health education on cognitive outcomes in sedentary older adults: the LIFE randomized trial. JAMA 2015;314(8):781–790. doi:10.1001/jama.2015.9617.
