A DIAGNOSIS of chronic fatigue syndrome (CFS), as defined in 1994¹ by the Centers for Disease Control and Prevention (CDC), Atlanta, Ga, requires unexplained fatigue for more than 6 months not due to continuing exertion, not resolved by rest, and accompanied by 4 or more of the following 8 symptoms: sore throat, tender lymph nodes, memory and concentration problems, joint pain, headache of a new type, unrefreshing sleep, and postexertional malaise lasting more than 24 hours. Chronic fatigue syndrome is characterized as a new onset of fatigue, serious enough to reduce daily activities by more than 50% and in the absence of any other medically identifiable disorders.^1,2 Patients with CFS exhibit marked impairment and sometimes have greater degrees of functional disability than do patients with other diseases such as type 2 diabetes mellitus, congestive heart failure, hypertension, acute myocardial infarction, major depression, relapsing or remitting multiple sclerosis,³ and acute infectious mononucleosis.⁴

Full blood counts, ESR, CRP, haematinics and markers for oxidative stress were measured for 33 patients diagnosed with chronic fatigue syndrome (CFS) and 27 age and sex matched controls. All participants also completed symptom questionnaires. CFS patients had increases in malondialdehyde (P <0.006), methaemoglobin (P <0.02), mean erythrocyte volume (P <0.02) and 2,3-diphosphoglycerate (P <0.04) compared with controls. Multiple regression analysis found methaemoglobin to be the principal component that differentiated between CFS patients and control subjects. Methaemoglobin was found to be the major component associated with variation in symptom expression in CFS patients (R(2) = 0.99, P <0.00001), which included fatigue, musculoskeletal symptoms, pain and sleep disturbance. Variation in levels of malondialdehyde and 2,3-diphosphoglycerate were associated with variations in cognitive symptoms and sleep disturbance (R(2) = 0.99, P <0.00001). These data suggest that oxidative stress due to excess free radical formation is a contributor to the pathology of CFS and was associated with symptom presentation.

Alcohol-induced hangover, defined by a series of symptoms, is the most commonly reported consequence of excessive alcohol consumption. Alcohol hangovers contribute to workplace absenteeism, impaired job performance, reduced productivity, poor academic achievement, and may compromise potentially dangerous daily activities such as driving a car or operating heavy machinery. These socioeconomic consequences and health risks of alcohol hangover are much higher when compared to various common diseases and other health risk factors. Nevertheless, unlike alcohol intoxication the hangover has received very little scientific attention and studies have often yielded inconclusive results. Systematic research is important to increase our knowledge on alcohol hangover and its consequences. This consensus paper of the Alcohol Hangover Research Group discusses methodological issues that should be taken into account when performing future alcohol hangover research. Future research should aim to (1) further determine the pathology of alcohol hangover, (2) examine the role of genetics, (3) determine the economic costs of alcohol hangover, (4) examine sex and age differences, (5) develop common research tools and methodologies to study hangover effects, (6) focus on factor that aggravate hangover severity (e.g., congeners), and (7) develop effective hangover remedies.