Risk factors for chronic fatigue syndrome: a case-control study.

Objective. To study various risk factors previously reported to be associated with chronic fatigue syndrome (CFS). Design. Case-control study. Setting. Metropolitan Atlanta CFS surveillance registry consisting of physicians and clinics that evaluate patients with fatiguing illness. Patients. Twenty-five CFS patients identified from the Centers for Disease Control and Prevention, Atlanta CFS study site, were matched by race, sex, and age to two randomly selected controls. Cases were further subgrouped by type of illness onset-sudden, occuring within a few days, or gradual, occuring over a longer period of time. Main outcome measures. A broad panel of risk factors previously associated with CFS. Results. CFS patients were significantly more likely to report a history of stress, persistent nasal symptoms, ear infections, and ingestion of B-complex vitamins during the year prior to the case's onset of illness. In addition, women patients were significantly more likely to have a hysterectomy. The subset of patients (n=17) who reported a gradual onset were significantly more likely than the patients reporting a sudden onset of illness or controls to report stressful events in the year prior to onset, certain dentual procedures, sinusitis, exposures to herbicides, pesticides, or insecticides, and a history of hysterectomy. We could not confirm previously reported associations of CFS with a history of asthma or eczema; exposure to sick animals; exposure to solvents, paint, or other chemicals; ingestion of raw-milk; or travel, occupation, or recreational activity. Conclusions. While no risk factors were identified that successfully distinguish CFS cases from controls, the data do suggest that gradual and sudden onset CFS constitute distinct subclasses of the syndrome. Future studies should subgroup people based on type of illness onset and further evaluate risk factors of interest, focusing on the role of stress, exposure to herbicides, pesticides, insecticides, and dental and medical histories. [ABSTRACT FROM AUTHOR]