Dementia is not a single disease but a general term for a group of symptoms affecting memory, thinking, and social abilities severely enough to interfere with daily life. Alzheimer's disease (AD), the most common type of dementia, accounts for 60-80% of dementia cases. As the global population ages, the number of people living with dementia is increasing rapidly, making it a major public health challenge. In this article, we will explore the symptoms of dementia and the latest advances in non-invasive brain treatments based on recent scientific research.
Common Symptoms of Dementia
Cognitive Symptoms
The core cognitive symptoms of dementia, especially in AD, involve progressive decline in multiple cognitive domains. Memory loss is often the earliest and most prominent symptom. In individuals with mild cognitive impairment (MCI), a transitional stage between normal aging and dementia, memory problems are noticeable but not severe enough to disrupt daily life. For example, Chan et al. (2021) studied older adults with MCI and found that they had difficulties in memory processing, which was reflected in reduced brain activity in memory-related regions measured by functional near-infrared spectroscopy (fNIRS).
Another important cognitive symptom is subjective cognitive decline (SCD), where individuals have a self-reported decline in memory or thinking abilities without obvious objective deficits in the early stage. Zhao et al. (2022) conducted a study on people with SCD and found that they often experience sleep quality issues, which is closely related to their cognitive complaints. As dementia progresses, more severe cognitive impairments occur, including problems with language (such as difficulty finding words), attention, and executive functions like planning, organizing, and making decisions.
Behavioral and Psychological Symptoms
Dementia is not just about cognitive decline; it also involves a range of behavioral and psychological symptoms. These can include depression, anxiety, irritability, aggression, and changes in personality. For example, individuals with AD may become apathetic, losing interest in previously enjoyed activities. These symptoms can significantly impact the quality of life of both the patients and their caregivers.
Sleep Disturbances
Sleep quality is often compromised in dementia. Zhao et al. (2022) found that in subjects with SCD, poor sleep quality was a common problem. Sleep disturbances in dementia can manifest as difficulty falling asleep, frequent awakenings during the night, and abnormal sleep-wake cycles, such as sleeping during the day and being awake at night. Poor sleep is not only a symptom but may also contribute to the worsening of cognitive functions, creating a vicious cycle.
Non-Invasive Brain Treatments for Dementia
Photobiomodulation Therapy (PBM)
Photobiomodulation therapy (PBM) is a promising non-invasive treatment that uses low-level light (usually in the near-infrared spectrum) to irradiate the brain. The mechanism of action of PBM, as described by Salehpour et al. (2018), involves several biological processes. Firstly, it acts on mitochondria in brain cells, enhancing their energy production (ATP synthesis) and reducing oxidative stress, which is harmful to cells. Secondly, PBM has anti-inflammatory effects, reducing the release of pro-inflammatory cytokines that contribute to brain inflammation, a key feature in the progression of AD. Additionally, it promotes neuroregeneration by stimulating the growth of new neurons and synapses, which are essential for cognitive functions.
Clinical studies have shown the effectiveness of PBM in improving various symptoms of dementia. Chan et al. (2021) investigated the effect of PBM on older adults with MCI. Using fNIRS, they found that after PBM treatment, there was an increase in brain activity in the prefrontal and temporal lobes, regions important for memory processing. Subjects also showed improved performance in memory tests, indicating that PBM can enhance memory functions in MCI individuals.
Zhao et al. (2022) focused on the impact of PBM on sleep quality in people with SCD. They conducted a randomized, sham-controlled study and found that PBM treatment significantly improved sleep quality, as measured by standard sleep questionnaires. Better sleep, in turn, may help slow down the progression of cognitive decline by allowing the brain to repair and consolidate memories during sleep.
Other Non-Invasive Brain Stimulation Techniques
Besides PBM, there are other non-invasive brain treatments discussed in the literature. Wu et al. (2022) reviewed several methods, including transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS). TMS uses magnetic fields to stimulate nerve cells in the brain. It has been shown to improve cognitive functions in some studies by modulating the activity of brain regions involved in memory and attention. tDCS, on the other hand, applies a weak direct current to the brain, which can enhance or inhibit neuronal activity depending on the polarity. These techniques, like PBM, aim to non-invasively modulate brain function to improve cognitive symptoms.
Mechanisms of Non-Invasive Brain Treatments
The beneficial effects of these non-invasive brain treatments on dementia symptoms are thought to occur through multiple interconnected mechanisms. At the cellular level, improving mitochondrial function is crucial as brain cells have high energy demands. When mitochondria work better, cells are more resistant to damage and can function more efficiently. Reducing oxidative stress and inflammation helps protect brain cells from the harmful effects of free radicals and inflammatory processes that contribute to neurodegeneration.
At the network level, enhancing synaptic plasticity (the ability of synapses to strengthen or weaken) and promoting neuroregeneration can help restore or maintain the brain's neural circuits responsible for memory, learning, and other cognitive functions. For example, PBM's promotion of new synapse formation can help compensate for the loss of synapses that occurs in AD.
Challenges and Future Directions
While the findings from these studies are promising, there are still several challenges in the field of non-invasive brain treatments for dementia. Wu et al. (2022) pointed out that many studies have small sample sizes, which limits the generalizability of the results. More large-scale, long-term clinical trials are needed to confirm the effectiveness and safety of these treatments over time.
Another challenge is the variability in treatment responses among individuals. Factors such as the stage of dementia, individual differences in brain structure and function, and the specific parameters of the treatment (such as light wavelength, intensity, and duration in PBM) may affect how well a person responds. Developing personalized treatment protocols based on individual characteristics could be an important future direction.
Additionally, the underlying mechanisms of dementia are complex, and it is likely that a combination of treatments will be needed to address multiple pathological processes. Combining non-invasive brain stimulation with other therapies, such as drug treatments or lifestyle interventions (like exercise and a healthy diet), may have synergistic effects and provide better outcomes for patients.
Conclusion
Dementia is a complex and debilitating condition with a range of cognitive, behavioral, and sleep-related symptoms. Non-invasive brain treatments, particularly photobiomodulation therapy, offer new hope by targeting the underlying biological mechanisms of neurodegeneration, such as mitochondrial dysfunction, inflammation, and neuroregeneration. Studies have shown their potential in improving memory, sleep quality, and cognitive functions in individuals with subjective cognitive decline, mild cognitive impairment, and Alzheimer's disease. However, more research is needed to overcome the current challenges and develop effective, widely applicable treatment strategies. As our understanding of these treatments grows, they have the potential to play a significant role in the management and prevention of dementia, improving the quality of life for millions of people worldwide.
References：
Wu C, Yang L, Feng S, Zhu L, Yang L, Liu TC, Duan R. Therapeutic non-invasive brain treatments in Alzheimer's disease: recent advances and challenges. Inflamm Regen. 2022 Oct 3;42(1):31. doi: 10.1186/s41232-022-00216-8. PMID: 36184623; PMCID: PMC9527145.
Salehpour F, Mahmoudi J, Kamari F, Sadigh-Eteghad S, Rasta SH, Hamblin MR. Brain Photobiomodulation Therapy: a Narrative Review. Mol Neurobiol. 2018 Aug;55(8):6601-6636. doi: 10.1007/s12035-017-0852-4. Epub 2018 Jan 11. PMID: 29327206; PMCID: PMC6041198.
Zhao X, Du W, Jiang J, Han Y. Brain Photobiomodulation Improves Sleep Quality in Subjective Cognitive Decline: A Randomized, Sham-Controlled Study. J Alzheimers Dis. 2022;87(4):1581-1589. doi: 10.3233/JAD-215715. PMID: 35491787.
Chan AS, Lee TL, Hamblin MR, Cheung MC. Photobiomodulation Enhances Memory Processing in Older Adults with Mild Cognitive Impairment: A Functional Near-Infrared Spectroscopy Study. J Alzheimers Dis. 2021;83(4):1471-1480. doi: 10.3233/JAD-201600. PMID: 33998541.
