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This study investigate bilingualism & cognition. The study was a meta analysis of studies. Inclusion criteria was studies investigating bilingualism in the elderly with relation to Alzheimer’s disease risk. 6 prospective cohort studies were selected and 8 retrospective studies were selected. Of the 14 studies, only 2 had a monolingual control group. 14 studies selected for analysis. Study indicated that bilingualism may be protective against memory decline in older adults.

Results:

Meta analysis indicates that one exception, the studies support the idea that bilingualism reduces risk of memory decline. . However, only a small sample of studies included, although selected studies generally of a good sample size (>500). Only two of the studies included participants with Alzheimer’s disease diagnosis. Moreover, only two studies had a control group. Further, two of the studies included only Hispanic subjects, which may have impacted results.

A notable limitation of the meta analysis is that it did not include any statistical analysis methods (i.e p value) and this is a significant limitation. Further large scale research is required to explore effects of bilingualism on cognition, and whether bilingualism may be protective against cognitive decline.

Abstract available here

Klimova, B., Valis, M., and Kuca, K. (2017). Bilingualism as a strategy to delay the onset of Alzheimer’s disease. Clin. Interv. Aging 12, 1731–1737.

This study investigated bilingualism & cognition. Study included 28 older adult participants – 14 monolingual participants and 14 bilingual participants (who had been bilingual since before age 11). All participants were subjected to a fMRI and had no diagnosed mental health conditions.

Results indicated:

Bilingual participants performed better on tasks and had better working memory (p<0.01) and better connectivity (p=0.002), compared with the monolingual group (p=0.17)

Results observed for other types of memory were not significant

Study size was small. Further large scale warranted. Study did not specify regarding bilingualism, as to whether participants spoke more than 2 languages, or whether certain type and complexity of language afford greater protection (i.e romance languages, Germanic languages etc.). Further research merited to explore effects of bilingualism on other types of memory.

Abstract available here

Grady, C. L., Luk, G., Craik, F. I., and Bialystok, E. (2015). Brain network activity in monolingual and bilingual older adults. Neuropsychologia 66, 170–181. doi: 10.1016/j.neuropsychologia.2014.10.042

In this study memory change over 6 years was assessed using a large scale sample (16, 638 elderly individuals born <1948) from Health and Retirement Study. Growth curve models were analysed with reference to memory recall of a 10 word list and levels of social integration (i.e with family, volunteering, marital status).

Results indicated:

Socialisation demonstrated as a predictor of slower memory decline (p<.01). 

In individuals with vascular disease, socialisation observed to be protective buffer ( (p< 0.05)

Memory amongst least socialised deteriorated at twice the rate of other participants, with association greatest amongst those with <12 years of education (p<0.07)

The study indicates that socialisation and levels of education may be protective factors for memory decline. The study also suggests that socialisation may reduce risk for memory decline in individuals with vascular diseases. The study did not use a robust means of measuring memory capability, such as MMSE. Results for socialisation as a predictor of slower memory decline not statistically significant. However, socialisation in individuals with vascular disease as a protective factor was observed to be statistically significant. More research required as to the mechanisms of how socialisation reduces risk of memory decline in vascular disease. Findings for education as a protective factor were observed to be statistically significant. More research required into to what level of education is most protective against memory decline.

Abstract can be viewed here

Ertel, K. A., Glymour, M. M., & Berkman, L. F. (2008). Effects of social integration on preserving memory function in a nationally representative US elderly population. American journal of public health, 98(7), 1215–1220.

The evidence for the relationship between alcohol, coffee and tea and cognitive deficits/benefits
has been confounding to date. This meta-analysis aimed to assess the current evidence
available in terms of the dose–response relationship between alcohol, coffee or tea
consumption and cognitive deficits.
Interestingly, it concluded that, based on the studies and data reviewed, whilst excessive
consumption of alcohol is known to have adverse health effects, light consumption of alcohol
(<11 g/day) and of coffee (<2.8 cups/day) are associated with reduced risk of cognitive deficits.
It also concludes that the cognitive benefits of green tea consumption increase with its daily
consumption.

The full text can be accessed here.

Alcohol, coffee and tea intake and the risk of cognitive deficits: a dose-response meta-analysis. Ran, L.S., Liu, W.H., Fang, Y.Y. et al. (2021) Epidemiology & Psychiatric Sciences. 30 (e13).