Bibliography
Hadanny A, Daniel-Kotovsky M, Suzin G, Boussi-Gross R, Catalogna M, Dagan K, Hachmo Y, Abu Hamed R, Sasson E, Fishlev G, Lang E, Polak N, Doenyas K, Friedman M, Tal S, Zemel Y, Bechor Y, Efrati S. Cognitive enhancement of healthy older adults using hyperbaric oxygen: a randomized controlled trial. Aging (Albany NY). 2020 Jun 26;12(13):13740-13761. doi: 10.18632/aging.103571. Epub 2020 Jun 26. PMID: 32589613; PMCID: PMC7377835.
At a glance
For many people, aging involves subjective memory decline. Indeed, many older people complain about poor memory and subsequently worry about further decline of their own cognitive abilities. For these reasons, an extensive amount of research has been carried out on pharmacological and non-pharmacological interventions intended to slow down, halt, or even reverse the trend of cognitive decline in the elderly. In short, no pharmacological intervention has yet been shown to be effective and only a few non-pharmacological interventions have shown some results, which have been of minor importance.
Researchers from the Shamir Medical Center in Israel conducted a randomized controlled trial (RCT), between 2016 and 2020, involving 63 healthy individuals over age 64. The aim of the study was to evaluate the efficacy of hyperbaric oxygen therapy in improving cognitive abilities. The results of the study highlighted significant improvement both of cognitive performance (particularly with respect to attention and information processing speed) and of cerebral blood flow in specific regions (mainly the frontal and parietal areas).
These results, though obtained from a small sample, encourage the practical use of hyperbaric oxygen therapy in the elderly to improve cognitive level. Moreover, they add evidence to studies that analyze the relationship between blood flow and cerebral function. This relationship represents the conceptual basis upon which further interventions can be developed for preserving or improving cerebral blood flow in the elderly.
The context
More than one half of people over age 60 worry about the progression of their own cognitive abilities. Indeed, it has been scientifically demonstrated that the normal aging process compromises functions like conceptual reasoning, information processing speed, attention level, and declarative memory. On the contrary, crystallized abilities like nondeclarative memory (e.g., size of vocabulary or procedural memory for small tasks) and general knowledge are barely compromised. The mechanisms though which this decline occurs are not yet fully understood. That said, poor cerebral blood flow in specific areas is associated with compromised cognitive function.
For these reasons, a growing body of studies are being conducted on potential interventions to slow down or stop the cognitive decline associated with the aging process. The pharmaceutical interventions put forth to date (e.g., hormonal or antihypertensive drugs) have not demonstrated any improvement, while interventions related to lifestyle factors have shown promising results. Physical exercise (especially aerobic exercise, which may improve cerebral blood flow) and the Mediterranean diet have proven to be particularly beneficial.
Given this background, a group of researchers conducted a study regarding the use of hyperbaric oxygen therapy for improving cognitive abilities in the elderly. Outcomes were measured both by means of cognitive tests (computerized and traditional ones) and through cerebral blood flow analysis. The study results will be useful for evaluating the practical use of hyperbaric oxygen therapy for the elderly.
The characteristics of the study
The study was structured as a randomized controlled trial (RCT), which involved 63 healthy subjects over age 64. The participants assigned to the treatment group underwent hyperbaric oxygen therapy (HBOT group, n=33), while the control group (n=30) received no active treatment. First, researchers assessed the cerebral blood flow through an MRI and the cognitive abilities through the Neurotrax computerized system, CANTAB computerized system, and traditional tests. Next, the HBOT group underwent a cycle of 60 sessions of hyperbaric oxygen therapy for 3 months (100 % oxygen at 2 ATA for 90 minutes). One week after the end of the cycle, the MRI scan and cognitive tests were repeated and the differences pre and post intervention were analyzed with respect to the control group.
The results
In comparison to the control group, the HBOT group’s overall general cognitive functions improved (net effect size=0.85), especially for attention (net effect size = 0.75) and processing speed (net effect size=0.79). Compared with the control group, cerebral blood flow in the HBOT group increased in the following areas: right superior medial frontal gyrus, right and left supplementary motor area, right and left middle frontal gyrus, left superior frontal gyrus, and the right superior parietal gyrus. All of these results were statistically significant.
Study limitations
The results were derived from a small sample. Even if promising, bigger studies are needed to confirm them. Moreover, even though the assessors were blinded, the patients were aware of the group to which they had been assigned. Finally, this study included healthy individuals and, therefore, results are not generalizable to persons affected by dementia or any other cognitive impairment.
The news and the prospects
This study opens the pathway for using hyperbaric oxygen therapy for cognitive decline in the elderly. Moreover, by adding evidence to the relationship between blood flow and cerebral functionality, it provides the theoretical basis for designing any intervention that could increase cerebral blood flow with the aim of counteracting cognitive decline.
Further studies are needed to confirm these results and hopefully they will include many more individuals and be multicentric. Moreover, no cost-effectiveness analyses have been published yet regarding this therapy. However, considering the small risk of adverse effects from hyperbaric oxygen therapy, the general practitioner might recommend it to combat cognitive decline.
Edited by Matteo Ratti and Riccardo Rescinito
Public Health Resident M.D.
