Evaluating How Red-light Therapy Applied to the Head Affects Symptoms, Daily Life, and Brain Activity in People With Dementia With Lewy Bodies

Dementia with Lewy bodies (DLB) is a neurodegenerative disease diagnosed primarily based on the presence of cognitive decline, which may include difficulties with memory, attention, and more. Additionally, at least two of the following symptoms are needed for a probable diagnosis of DLB, and at least one for a possible DLB diagnosis (McKeith et al. 2017 and 2020): * Fluctuations in cognition, attention, and/or alertness * Visual hallucinations * Spontaneous parkinsonism * REM sleep behavior disorder Patients with DLB can experience cognitive deficits that can fluctuate and can vary for each patient. These may include deficits in memory, executive functions (planning and organizing), attention, visual processing, and language. This study aims to evaluate the effect of red-light therapy, delivered using a helmet that contains small LED lights, in patients with DLB. Participants' cognitive functions, clinical symptoms, quality of life and functional cerebral connectivity will be evaluated before starting therapy and again after three and six months of twice daily therapy use. As DLB also indirectly affects caregivers, the caregiver's quality of life and burden will also be evaluated before and at three and six months of therapy use by the participant. The study's inclusion period is 24 months and the duration of participation for each patient is 8 months (+/-10 days) maximum.

Inclusion criteria: * Man or woman, 50 years or older * Probable DLB diagnosed according to the criteria of McKeith et al., 2017, or the criteria of McKeith et al., 2020 for prodromal DLB * Score on the Mini Mental State Examination (MMSE; Folstein et al., 1983) ≥ 18/30 at their last medical visit * Good mastery of the French language * Accompanied by a caregiver or a person able to provide information about them (interview, by telephone). * Able to understand the objectives and risks associated with the research and to give informed consent, dated and signed * Covered by a social health insurance plan * Having a head circumference between 54 and 62 cm. Exclusion criteria: * Not able to understand the objectives and risks related to research and to give informed consent * Presence of another neurological disorder, including but not limited to brain tumors, stroke with potential cognitive impairment, or diagnosis of another progressive neurological disease (e.g., Alzheimer's disease, Parkinson's disease, etc.), and as determined by the investigator * Having an MMSE score \< 18 at the screening visit * Unable to undergo a brain MRI due to medical reasons * Participants whose follow-up would likely be disrupted during the study period (e.g., due to planned relocation or other reasons) * Insufficient proficiency of the French language * Participants experiencing an emergency of life-threatening situation * Alone, without a caregiver present * Participants presenting with a head/scalp injury * Participants with a silicone allergy * Participants with cranial/skull shape abnormalities * Participants with a head circumference outside the range of 54-62 cm * Participants requiring life support, continuous monitoring, and/or implanted medical devices (AIMD) * Participants taking the antiepileptic Keppra (Levetiracetam) * Participants whose anticholinesterase treatments have been changed within the past 2 months * Participants whose antipsychotic treatments have been changed within the last 15 days * Pregnant or breastfeeding women