Fatigue in Healthy Individuals

Overview

Background: * People with many different diseases have symptoms of fatigue, which is a general sense of tiredness; however, the causes are not fully understood. Fatigue symptoms may be related to a person s level of fitness, health, and blood chemistries. * Researchers are studying the potential role of plasma cytokines (signaling molecules) and hypothalamic-pituitary-adrenal (HPA) axis (part of the neuroendocrine system that controls stress) functioning in symptoms of fatigue. Objectives: * To characterize the symptoms of fatigue in healthy individuals. * To collect information on fatigue, pain, depression, stress, sleepiness, and quality of life from healthy adults of all ages. * To compare results obtained from people with various illnesses to better understand possible causes of fatigue that are associated with those diseases. Eligibility: * Physically and mentally healthy volunteers18 years of age or older who can speak and read the English language. * Exclusion criteria include individuals with a disease or condition causing significant fatigue (congestive heart failure, cancer, or sleep disorders), individuals taking medicines that cause fatigue (beta blockers, diuretics, or narcotics), and individuals who have a major psychiatric condition (major depression, anxiety disorder, or schizophrenia). * The following individuals may not participate: those who have two more alcoholic drinks per day, who use illicit drugs, or who drink more than 4 cups of coffee, 8 cups of soda or tea, or similar amounts of other caffeine-containing beverages a day, or eat more than 1 pound of chocolate per day; and individuals who worked evenings or night shifts in the past month. * Women who are pregnant or breastfeeding are not eligible. Design: * Participants must make two outpatient visits to the Clinical Center. Each visit will last 5 hours and participants must refrain from smoking and consuming alcohol and caffeine for at least 24 hours. * During the first study visit, researchers will conduct the following tests: * Psychiatric interview, medical history, pregnancy test, and drug test. * Urine test to measure the levels of stress hormones. * Questionnaires that measure fatigue, pain, depression, stress, daytime sleepiness, and activity. * Physical fitness test, including strength tests, walking tests, and physical activity monitoring. * Before the second study visit, patients must refrain from smoking and consuming caffeine and alcohol for at least 24 hours and have nothing, even water, by mouth after midnight. During the second study visit, the following tests will be conducted: * Stress hormone test (participant will receive a cortisol-releasing hormone). * Four intravenous blood draws to determine cytokine profiles, gene expression, and levels of stress hormones (immune and gentic analysis). * Participants will receive a small financial compensation for participation in the study.