The intervention group used the Graphene Far Infrared Intervention (GFII), in which a caregiver who had undergone standardized training wore a graphene cap that could heat up to 40°C on the elderly. The cap was worn by the elderly for a fixed period of time each day and removed after approximately 40 minutes. During the time of wearing the cap, the elderly can perform any activity (e.g., reading the newspaper, watching TV) within the length of the power cord in a sitting, lying, standing position, etc.

The placebo control group used ordinary hats that could be heated to about 40°C and were worn to the head of the elderly by caregivers who had undergone standardized training. The elderly wore the heat generating cap for a fixed period of time each day and removed it after about 40 minutes. During the period of wearing the cap, the elderly can sit, lie down, stand in the position of the length of the power cord, and carry out any activities (e.g., reading newspaper, watching TV)

The GFII involved the use of a custom-made graphene therapy cap. The cap consisted of 3 parts: the main body of the cap, the thermostat and the power adapter. One end of the thermostat was connected to the main body of the cap, and the other end was connected to the power adapter; the adapter was plugged into a 220 V household power outlet. This turned on the cap, and the temperature could be adjusted. The light energy conversion rate of the graphene coating material used in the cap reached 90%, generating a temperature of 40 °C. Five caregivers were responsible for providing care for the elderly individuals. We will provided standardized training on the GFII to their caregivers. Each caregiver was responsible for assisting with the intervention of the elderly individuals that they usually cared for.

Depression was assessed by the Self-Rating Scale for Subjective Cognitive Decrease (SCD). The scale consists of 10 items that are scored from 1 (no change) to 3 (significant increase) based on the patient's self-reported subjective cognitive decompensation. A higher total score indicates more severe subjective cognitive decompensation.

Cognitive function was assessed with the short form of the Montreal Cognitive Assessment (s-MoCA). The items are used to examine function in 6 cognitive domains (i.e., visuospatial/executive function, attention, language, abstraction, delayed memory, and orientation). If the number of years of education is less than or equal to 12, the total score is increased by 1 point. The total score ranges from 0 to 18: scores less than or equal to 11 indicate probable mild cognitive impairment (MCI), and scores less than or equal to 4 indicate probable Alzheimer's disease (AD).

Depression was assessed with the Patient Health Questionnaire (PHQ-9). The PHQ-9 contains nine items scored on a scale from 0 (not at all) to 3 (almost every day) based on the self-reported frequency of depressive symptoms in the past 2 weeks. The total score ranges from 0 to 27, and scores above 10 indicate probable depression symptoms.