Onset Patterns and Course of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract

Background: Epidemiologic studies of myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS) have examined different aspects of this disease separately but few have explored them together. Objective: Describe ME/CFS onset and course in one United States-based cohort. Methods: One hundred and fifty subjects fitting Fukuda 1994 CFS criteria completed a detailed survey concerning the initial and subsequent stages of their illness. Descriptive statistics, graphs, and tables were used to illustrate prevalence and patterns of characteristics. Results: The most common peri-onset events reported by subjects were infection-related episodes (64%), stressful incidents (39%), and exposure to environmental toxins (20%). For 38% of subjects, more than 6 months elapsed from experiencing any initial symptom to developing the set of symptoms comprising their ME/CFS. Over time, the 12 most common symptoms persisted but declined in prevalence, with fatigue, unrefreshing sleep, exertion-related sickness, and flu-like symptoms declining the most (by 20-25%). Conversely, cognitive symptoms changed the least in prevalence, rising in symptom ranking. Pregnancy, menopause, and menstrual cycles exacerbated many women's symptoms. Fatigue-related function was not associated with duration of illness or age; during the worst periods of their illness, 48% of subjects could not engage in any productive activity. At the time of survey, 47% were unable to work and only 4% felt their condition was improving steadily with the majority (59%) describing a fluctuating course. Ninety-seven percent suffered from at least one other illness: anxiety (48%), depression (43%), fibromyalgia (39%), irritable bowel syndrome (38%), and migraine headaches (37%) were the most diagnosed conditions. Thirteen percent came from families where at least one other first-degree relative was also afflicted, rising to 27% when chronic fatigue of unclear etiology was included. Conclusions: This paper offers a broad epidemiologic overview of one ME/CFS cohort in the United States. While most of our findings are consistent with prior studies, we highlight underexamined aspects of this condition (e.g., the evolution of symptoms) and propose new interpretations of findings. Studying these aspects can offer insight and solutions to the diagnosis, etiology, pathophysiology, and treatment of this condition.

Keywords: chronic fatigue syndrome; course; epidemiology; myalgic encephalomyelitis; natural history; onset; systemic exertion intolerance disease.

Figure 1

Impact of hormonal events on ME/CFS in women. Only subjects identifying themselves as female were asked these items. 120 out of 121 women responded. The number answering for each event varies depending on both response rate and each woman's circumstances. “Exogenous hormone administration” refers to any form of reproductive hormones (e.g., pills, patch, implants, etc.) taken for contraception, relief of menopausal symptoms, or treatment of any medical condition.

Figure 2

Self-reported functional level during various periods of illness. Numbers 1–7 on x-axis correspond to the following functional levels: (1) I am not able to work, go to school, or do anything, and I am bedridden. (2) I can walk around the house, but I cannot do light housework. (3) I can do light housework, but I cannot work or go to school part-time. (4) I can only work part-time at work or school or on some family responsibilities. (5) I can work or go to school full time, but I have no energy left for anything else. (6) I can work or go to school full time and finish some family responsibilities but I have no energy left for anything else. (7) I can do all work, school, or family responsibilities without any problems with my energy.

Figure 3

Fatigue questionnaire scores vs. duration of illness. Each point represents one subject. (A) Total Multi-dimensional Fatigue Inventory-20 (MFI-20). (B) Average Fatigue Severity Scale (FSS) scores.

Figure 4

Fatigue questionnaire scores vs. age of subject. Each point represents one subject. (A) Total Multi-dimensional Fatigue Inventory-20 (MFI-20). (B) Average Fatigue Severity Scale (FSS) scores.