Photobiomodulation promising in mild cognitive impairment

A small case series from the Chinese University of Hong Kong suggests that transcranial photobiomodulation (tPBM) may improve frontal lobe cognitive functions and mental health of older adults (OAs) with mild cognitive impairment (MCI).

tPBM is a non-invasive biological stimulation technique that applies light from the red to near-infrared spectrum (600–1,100 nm) to the brain through the skull. tPBM’s proposed neurobiological effects occur primarily at the mitochondrial level and are mediated via enhanced energy production and oxygen supply to nerve cells. Although some studies suggest that tPBM improves frontal lobe cognitive functioning in healthy adults and patients with traumatic brain injury, as well as alleviating depressive and anxiety symptoms in patients with psychological disorders, its effect on OAs with MCI remains unknown.

Present study investigated the effect of tPBM on three older adults with non-amnestic MCI who demonstrated impairment in the frontal lobe cognitive functions and depressive and anxiety symptoms at baseline. Each OA received 18 20-minute-long tPBM stimulation sessions over the course of 9 weeks. [Front Psychol 2023;doi:10.3389/fpsyg.2022.1095111]

OA1 was a 55-year-old female who showed signs of cognitive dysfunction associated with the frontal lobe at baseline. She exhibited substantial intrusion errors in the Hong Kong List Learning Test (HKLLT), placing her within moderately to severely impaired range, and intrusion and perseveration errors in the Category Fluency Test (CFT), placing her within the severely impaired range. After tPBM intervention, OA1’s HKLLT and CFT performance fell within the normal range.

OA1 also reported a moderate to severe level of depressive symptoms (Chinese version of the Geriatric Depression Scale—Short Form [CGDS-SF] total score of 11) at baseline, which improved to a mildly depressed level (CGDS-SF total score of 6) after the intervention. In addition, she reported a severe level of anxiety symptoms (Geriatric Anxiety Scale—10 Item Version [GAS-10] total score of 15) at baseline but a mild level (total score of 8) after tPBM. Her improved self-rated anxiety symptoms were in line with her reported subjective feeling of reduced nervousness and compulsive acts, such as repeated checking behavior, after the intervention.

OA2 was a 62-year-old retired female who had HKLLT intrusion errors within the borderline range and CFT perseveration errors within the severely impaired range. After the intervention, her HKLLT intrusion errors improved to the high average range while her CFT perseveration errors remained within the same range. According to her feedback, she experienced some improvements in her memory and became more fluent and experienced less difficulty when giving a speech during the course of the intervention.

After the intervention, OA2’s mild depressive symptoms improved to a normal level (from CGDS-SF of 5 to 0) and her initially minimal level of anxiety further decreased from GAS-10 score of 4 to 1.

OA3 was a 70-year-old retired male who had difficulty remembering appointments, family occasions, holidays, and medications at baseline, which he was able to remember independently after tPBM. At baseline, he had mildly impaired CFT intrusion error scores, which improved to the average range after the intervention. However, he made more perseveration errors in the CFT, with his rank dropping from the low average to moderately impaired range after the intervention. OA3’s intrusion errors in the HKLLT remained within normal limits after the intervention, although his percentile rank decreased slightly from the high average to the average range. His reported depressive symptoms were slightly reduced from mild to normal level, while his anxiety symptoms increased from a minimal to a mild level.

“After tPBM, our subjects demonstrated various levels of improvement in their frontal lobe cognitive functions, with some impaired functions falling into the average range, while improvements were also noted in their depressive/anxiety symptoms,” summarized the researchers.