The goal of this multi-site double blinded randomized sham-controlled Phase II clinical trial is to test a novel, relatively low cost, low risk, and potentially high impact therapeutic intervention in older adults who are at increased risk for Alzheimer's disease. The intervention involves transcranial and intranasal delivery of near infrared (NIR) light via light emitting diodes, aka photobiomodulation (PBM). The overall hypothesis, based on animal and pilot studies, is that exposure to NIR stimulation will have beneficial effects on brain health via influence on mitochondrial function as measured by changes in 31Phosphorous (31P) MRS-based markers of ATP, neural network changes in functional connectivity (rs-fMRI), and improved cognitive performance. To test this hypothesis, 168 older adults with subjective cognitive complaints, and a first-degree family history of Alzheimer's disease will be randomized to sham or real treatment groups. Neuroimaging and cognitive outcome measures will be obtained, before and after a 12-week intervention involving transcranial and intranasal NIR-PBM. The intervention protocol will involve "lab" and "home" sessions, and a 3 month post-intervention follow-up. This trial will determine: 1) whether NIR stimulation, relative to sham, improves performance on memory and executive tasks sensitive to hippocampal and frontal brain function in older adults with increased risk for Alzheimer's disease; 2) whether NIR stimulation, relative to sham, enhances brain function and connectivity measured by changes in MRS phosphorous ATP and resting state functional connectivity; and 3) how differences in demographic, neuroimaging, and Alzheimer-related risk factors influence the brain response to NIR stimulation versus sham in older adults with increased risk for Alzheimer's disease. Results will provide key insights into whether this novel NIR intervention can enhance cognition in older adults with increased risk for Alzheimer's disease and will provide the necessary data for a future Phase III randomized clinical trial.

This multi-site randomized sham-controlled trial proposes to test a novel, non-invasive, low risk and low-cost brain stimulation approach for enhancing cognition and brain health in cognitively normal older adults who are at increased risk for Alzheimer's disease. The intervention involves transcranial and intranasal delivery of near-infrared light (NIR; 808-904 nm) via light emitting diodes placed on the scalp or intranasally using a dosing that resulted in positive effects in our pilot studies. We plan to test the hypothesis that targeted NIR stimulation will have positive effects on brain health via influence on mitochondrial function as measured by changes in Magnetic Resonance Spectroscopy (MRS)-based markers of adenosine triphosphate (ATP), neural network changes as indexed by changes in functional connectivity based on resting state-fMRI (rs-fMRI), and improved cognitive performance. We plan to randomize 168 older adults, ages 65-89 years, to Active or Sham intervention conditions. To be included, participants must have subjective cognitive complaints, based on an index of Subjective Cognitive Impairment (SCI), and a family history of Alzheimer's disease in a first degree relative. Performance on standardized neuropsychological measures must be unimpaired psychometrically. The intervention itself will last for 12 weeks and include lab sessions (16 total) and daily at home sessions. In the lab, both transcranial and intranasal delivery of NIR light will be delivered using Medx and Vielight stimulation technologies, whereas the daily at home sessions will involve intranasal stimulation only. The sham and active conditions are identical in all respects except that sham devices will not deliver NIR stimulation. The primary outcome is an episodic memory measure involving spatial navigation that is linked to hippocampal function, sensitive to mild cognitive impairment (MCI) and Alzheimer's disease, and an analogue to the Morris Water maze. Secondary outcomes include executive function tasks and neuroimaging indicators of ATP function (31-P MRS) and connectivity changes based on resting state-fMRI. Exploratory outcomes include 'traditional' neuropsychological measures that are used clinically, along with measures and indices (e.g., apolipoprotein E [APOE-4] status) that might potentially mediate or moderate study outcome. Assessments will occur at baseline (Month 1), after 12 weeks of intervention (Month 4), and 3-month post intervention (Month 7). Imaging outcomes will be assessed only at baseline and at Month 4. Our primary aim is focused on cognition and will test whether NIR intervention, relative to sham, will produce pre-post improvement on tasks of recent memory (primary outcome) and executive function in older adults who are at increased risk for Alzheimer's disease. Our secondary aim is focused on neuroimaging and will test whether NIR intervention, relative to sham, will increase functional connectivity as indexed by resting state fMRI (secondary outcome) and enhance brain markers of MRS-ATP (secondary outcome). The 3rd aim is exploratory and will evaluate how baseline demographic, genetic, neuroimaging and other factors influence individual differences in cognitive outcome for NIR intervention.

Inclusion Criteria:

• Age 65-89 years, at least 8th grade education, community dwelling
• Subjective report of cognitive complaints with scores >16 on the Cognitive Change Index (CCI-20)
• No evidence of dementia or mild cognitive impairment based on cognitive screening (i.e., Montreal Cognitive Assessment (MoCA) score within normal limits for age, education and sex using the National Alzheimer's Coordinating Center (NACC) Uniform Data Set (UDS) norms.
• No psychometric evidence of cognitive impairment based on performance on the Neuropsychological Battery from the NACC Unified Data Set, version 3. Scores on these measures cannot be lower than 5th percentile below normative values based on age, education, and gender.
• Reading at > 8th grade level based on the reading subtest of the Wide Range Achievement Test- IV.
• Global Clinic Dementia Rating (CDR) score must be 0
• Family history of dementia/probable Alzheimer's disease in first degree relative (parents, children, siblings)
• Willingness to be randomized to Sham or Active Intervention
• Can devote 12 weeks to the intervention with additional time for pre and post testing
• Normal functional behavior in terms of daily activities, based on the Functional Activities Scale
• Able to perform cognitive and emotion measures on a computer
• In line with recommendations of the Subjective Cognitive Decline (SCD) task force an informant must be available for two reasons: a) to provide information about the participant's complaints using the informant version of the CCI-20, and b) to corroborate normal IADL's on the Functional Activity Questionnaire.

Exclusion Criteria:

• Sensory loss (vision, hearing) or motor deficits that would preclude participation in the experimental tasks or neuropsychological assessment
• English as a second language
• Inability to undergo brain imaging due to claustrophobia or implants such as pacemakers, heart valves, brain aneurysm clips, orthodontics, non-removable body jewelry, or shrapnel containing ferromagnetic metal
• Previous major strokes or other known significant brain abnormalities or diseases affecting the brain and/or cognition (e.g.,Parkinson disease, multiple sclerosis, seizure disorder, brain surgery, moderate traumatic brain injury (TB)I, Rapid Eye Movement (REM) Behavior Sleep Disorder, untreated sleep apnea, etc.)
• Unstable and uncontrolled medical conditions (metastatic cancer, HIV, moderate-severe kidney disease, uncontrolled diabetes, uncontrolled hypertension, severe cardiac disease, etc.). No current cancer diagnosis.
• Current or past history of major psychiatric disturbance including schizophrenia, or active psychosis, bipolar disorder, current major depressive episode, current alcohol or substance abuse or history thereof within the past six months.
• Use of antipsychotics, sedatives, or other medications with significant anticholinergic properties (due to potential influence on memory)
• Use of prescribed 'memory enhancing' medications such as Aricept or Namenda
• Use of photo-sensitive medications such as steroids or retin-A within 15 days of the study intervention.
• Previous participation in a cognitive training study within the last 6 months or current involvement in another study involving cognitive, physical or other intervention at the time of participation

From enrollment until 3 months post intervention (approximately 6 months total).

Primary limitation pertained to frequency of stimulation. For future trials, we recommend 3-4 sessions per week throughout the entire 12 weeks.

Use of a sham-controlled approach provides stringent experimental control, enabling the investigators to control for placebo/expectations, behavioral activation (engaging in study procedures) and practice effects related to repeated administration of the same cognitive tasks.

The MedX and Vielight devices used for delivery of active and sham NIR stimulation are identical in all respects regarding design, warmth and operation, except that no stimulation is delivered by the sham devices. Because NIR light is invisible, participants will not be able to discern if receiving active or sham stimulation. The participants, interventionists, and outcome assessors will be blinded to the participants' intervention status: Active vs Sham. At completion of the study, all participants will receive a Placebo Control Questionnaire that asks questions pertaining to what group the participant had been assigned. This data will be examined to determine the effectiveness of blinding.