Fish are an important dietary source of omega-3 fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)
Omega-3 fatty acids play a role in the growth and development of neuronal tissue and have demonstrated cognitive benefits across the lifespan.
Omega-3 fatty acids also modulate sleep via melatonin and prostaglandin production, and fish consumption is associated with improved sleep in epidemiological studies.
Lastly, poor quality of sleep has been associated with worse cognitive function in children and adults in several studies.
Given the relationships between fish oils and cognition, fish oils and sleep, and sleep and cognition, researchers conducted a study to clarify the interactions among these three variables.
The study involved 541 Chinese school-aged children.
There were three goals of the study
Participants completed a food frequency questionnaire to assess fish consumption between the ages of 9 and 11.
Sleep quality and cognitive function were evaluated at age 12. Of the 541 children, 137 (25%) ate fish at least once a week, 315 (58%) ate fish 2–3 times per month and 89 (16%) never or seldom ate fish.
When compared with no fish consumption, fish consumption two times per month or more was significantly associated with higher verbal, performance, and full-scale IQ (all p<.05).
These associations held true after adjusting for 13 sociodemographic covariates.
There was a dose-response relationship between fish consumption frequency and IQ scores, such that those who ate fish weekly scored 4.80 points higher on full-scale IQ, and those who ate fish at least twice a month scored 3.31 points higher, than those who seldom or never ate fish.
More frequent fish consumption was also significantly and independently associated with less sleep disturbance, such that those who ate fish weekly had a total sleep disturbance score 4.49 points lower, and those who ate fish at least twice a month had a score 3.01 lower, than those who seldom or never ate fish.
Children with fewer sleep disturbance problems were more likely to have higher cognitive functioning.
Mediation analysis showed that sleep quality partially mediated the association between fish consumption and verbal IQ, but it did not mediate the association between fish consumption and performance IQ.
This study confirms findings of previous studies that have shown fish consumption to improve sleep and cognition.
It adds the novel finding that sleep might partially mediate the association between fish consumption and higher IQ.