Comparing FMS and CFS

The following is a useful guide to help identify the differences and similarities between Chronic Fatigue Syndrome (CFS) and Fibromyalgia Syndrome (FMS).

In the past fibromyalgia was called 'fibrositis' and Chronic Fatigue Syndrome has now replaced the terms 'chronic mononucleosis' and 'chronic Epstein-Barr syndrome'. In Victorian times CFS was probably known as 'neurasthenia' and 'nervous exhaustion'.

For many people the diagnosis CFS and FMS seems to be interchangeable. However, there are certain symptoms like fever and swollen glands that are found in a higher percentage in CFS patients than those with FMS.

One similarity is in age and gender. The majority of diagnosed cases of CFS occur in women, most of whom are 25 to 45 years old. FMS strikes mostly women between the ages of 20 and 50.

Prevalence of CFS

Two studies using the same working definition and including a medical work-up have estimated the prevalence to be approximately 200 per100,000 of the general population. In Japan, a study found that the proportion of CFS cases was 14.8% for both sexes, and tended to be slightly higher among females than males. There was no relation to age. (2)

According to the Centers for Disease Control, the "...minimum prevalence rates for the period 1 September 1989 to 1 September 1991 ranged from 2.0 to 7.3 per 100,000 of the general population..... More than 80% of the CFS cases were female, most were white, and their average age at onset was approximately 30 years. (3)

Prevalence of FMS

A British study calculated annual incidence of fibromyalgia in females was 583 per 100,000. (4) In the US the prevalence of fibromyalgia according to a 1995 study was 2.0% for both sexes, 3.4% for women, and 0.5% for men. (5)

Main Complaint

The main complaint in Chronic Fatigue Syndrome (CFS) is the extreme and around-the- clock fatigue. The smallest physical exertion can totally deplete a person confining the person to bed for days. There is no official clinical test to diagnose CFS. Instead, doctors rule out other diseases before making a Chronic Fatigue Syndrome diagnosis.

Fibromyalgia, on the other hand, is an arthritis-related condition. The primary complaint is round-the-clock pain that rarely goes away. In contrast to CFS, FMS can be diagnosed according to the criteria set forth by the American College Rheumatology.

Common Symptoms

In a 1990 conference on CFS and FMS, Carol Jessop MD (6) gave the following symptoms has beeing common in both conditions. These findings are from seeing thousands of patients in her practice.

100% of the patients with FMS have muscle pain as part of their symptom picture. Part of the diagnosis is finding 11 out of 18 tender points. On the other hand, many CFS patients do not have enough tender points to satisfy the standard criteria for fibromyalgia.

Also, irritable bowel syndrome is probably more common in FMS.

Physical Findings

Dr. Jessop in her practice found the following common physical findings between CFS and FMS. The data is from 1,324 patients of which 75% were female.

Cognitive Impairment

The difference in cognitive impairment between CFS and FMS is one of degree. Overall, cognitive impairment is less debilitating in FMS than in CFS. The following table lists the different percentages in cognitive impairment between the two. (7)

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