Patient-Centered Assessment of Symptoms and Outcomes

Background: The cause of fatigue is not well understood. It can be felt differently by different people. Some people think there are different types of fatigue, with different causes. Researchers think a therapy to treat one type of fatigue in one condition should be able to treat that type of fatigue in other conditions. Objective: To understand the types of fatigue. Eligibility: Adults 18 and older who have felt fatigue for more than a month, and non-fatigued adults Design: Participants will be screened with a physical exam, their medical history, a vision test, and blood and urine tests. Participants will begin to track the foods they eat. This study will involve up to 10 visits. Each visit will last no more than 4 hours. In Stage 1, participants will have an interview, fill out questionnaires, and play computer games. They will take walking and handgrip tests. They will give blood, urine, and saliva samples. They will wear a wrist monitor at home for 7 days and write down their activities. They will be put into a group: fatigue or non-fatigued control. In Stage 2, participants will answer questionnaires and give a blood sample. They will have heart tests. They may take exercise and lung function tests that include wearing a nose clip. They may have an optional brain MRI: They may wear an electrode cap on their head during the scan to measure brain activity. They will lie on table that slides into a cylinder. They may perform tasks in the scanner. After the study, participants might be contacted about other studies.