Photobiomodulation in Chronic Fatigue Syndrome

Fatigue will be assessed using validated self-reported instruments to evaluate the effect of photobiomodulation therapy on chronic fatigue symptoms.

The Fatigue Severity Scale (Fatigue Severity Scale) is a 9-item questionnaire that measures the impact of fatigue on daily functioning. Each item is scored on a 7-point Likert scale, and the final score is calculated as the mean of all items, with higher scores indicating greater fatigue severity.

The Multidimensional Fatigue Inventory (Multidimensional Fatigue Inventory) is a 20-item instrument assessing five dimensions: general fatigue, physical fatigue, mental fatigue, reduced activity, and reduced motivation. Each domain is scored on a 5-point Likert scale, with higher scores indicating increased fatigue.

Quality of life will be assessed using either the Medical Outcomes Study 36-Item Short Form Health Survey (Short Form-36 Health Survey) or the World Health Organization Quality of Life Brief Version (World Health Organization Quality of Life-BREF).

The Short Form-36 Health Survey evaluates eight domains including physical functioning, bodily pain, vitality, and mental health. Scores range from 0 to 100, with higher scores indicating better quality of life.

The World Health Organization Quality of Life-BREF consists of 26 items covering physical, psychological, social, and environmental domains, with higher scores indicating better perceived quality of life.

Functional capacity will be assessed using the Six-Minute Walk Test (Six-Minute Walk Test). This test measures the total distance (in meters) a participant can walk in six minutes on a flat surface and reflects submaximal aerobic capacity and endurance.

Pain intensity will be measured using the Visual Analog Scale (Visual Analog Scale), a 10-centimeter horizontal line ranging from "no pain" to "worst imaginable pain." Scores are recorded in centimeters, with higher scores indicating greater pain intensity.

Sleep quality will be evaluated using the Pittsburgh Sleep Quality Index (Pittsburgh Sleep Quality Index). This 19-item questionnaire assesses sleep quality over the past month across seven components. Global scores range from 0 to 21, with higher scores indicating poorer sleep quality.

Psychological well-being will be assessed using either the Hospital Anxiety and Depression Scale (Hospital Anxiety and Depression Scale) or the Beck Depression Inventory (Beck Depression Inventory).

The Hospital Anxiety and Depression Scale includes 14 items divided into anxiety and depression subscales, each scored from 0 to 21.

The Beck Depression Inventory is a 21-item self-report questionnaire with scores ranging from 0 to 63, where higher scores indicate more severe depressive symptoms.

Follow-up assessments will be conducted to determine whether improvements in fatigue, pain, and functional capacity are sustained after completion of the intervention.

Safety and tolerability will be assessed by monitoring participant-reported discomfort, skin irritation, or other minor side effects occurring during or after Photobiomodulation therapy sessions.

All adverse events will be recorded and categorized by type, severity, duration, and relationship to the intervention. Serious adverse events will be reported immediately in accordance with regulatory requirements.