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Findings

A substantial number of Canadians report symptoms of conditions that cannot be definitively identified through physical examination or medical testing.¹  Known as “medically unexplained physical symptoms,” or “MUPS,” they characterize conditions such as chronic fatigue syndrome, fibromyalgia and multiple chemical sensitivity.^2-5  The lack of consistent explanations from physical and laboratory assessments has caused confusion and controversy about these conditions.  Many people, including some health care professionals, do not believe that these conditions exist, attributing the symptoms to a variety of other causes.  However, for the people who are affected, the symptoms are real and frequently debilitating.

Based on information from the 2002 and 2003 Canadian Community Health Survey (CCHS), this article describes the prevalence of MUPS and the characteristics of Canadians who report having these conditions.  It also examines co-morbidity with psychiatric disorders, and associations with dependency, self-perceived mental health, and the use of health care services.

Symptoms overlap
More than one million
Dependency
Mental health and well-being
Mental disorders
Consultations with health care providers

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Symptoms overlap

Chronic fatigue syndrome (CFS), fibromyalgia (FM) and multiple chemical sensitivity (MCS) are characterized by clusters of symptoms originating from several different organ systems, which remain medically unexplained. These conditions share key symptoms, and individuals often meet the criteria for more than one of them. Chronic fatigue syndrome (CFS), fibromyalgia (FM) and multiple chemical sensitivity (MCS) are characterized by clusters of symptoms originating from several different organ systems, which remain medically unexplained.⁶  These conditions share key symptoms,^1-4 and individuals often meet the criteria for more than one of them.

Extreme tiredness is the most salient symptom of chronic fatigue syndrome.  Also known as myalgic encephalomyelitis, CFS is mostly determined by negative diagnosis; that is, a patient is said to have the syndrome only when other medical conditions with similar symptoms have been ruled out.^5,7

The diagnostic criterion for fibromyalgia is pain lasting three months or more in at least 11 of 18 specified areas.⁵  The pain is often, but not necessarily, accompanied by symptoms that are common to CFS, such as cognitive impairment, headache, sore throat, weakness, fatigue, depression and digestive problems.^5,7

Those who suffer from multiple chemical sensitivity develop a variety of symptoms when they are exposed to synthetic chemicals in doses that usually have no noticeable effect.  Among the symptoms triggered by chemical exposure are changes in heart rate, difficulty breathing, rashes, nausea, headache, and confusion.⁸  The duration, severity and nature of these reactions vary greatly, and symptoms may last for days.

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More than one million

According to the 2003 Canadian Community Health Survey, 5% of Canadians aged 12 or older, an estimated 1.2 million people, reported having been diagnosed with at least one of three MUPS conditions:  1.3% reported CFS; 1.5%, FM; and 2.4%, MCS (Table 1) .  Among individuals with MUPS, about 14% had at least two of the three conditions (data not shown).

For each of the three conditions, prevalence rates for women were more than twice those for men (Table 1).  As well, the overall prevalence of MUPS rose with age from 1.6% at ages 12 to 24 to 6.9% at ages 45 to 64.  This pattern was similar for each of the three conditions.  Even when variables such as household income, education and marital status were taken into account, the age-sex differences remained significant (data not shown).

The likelihood of reporting MUPS was associated with socio-economic status.  The overall prevalence rate and the rate for each of the three conditions were significantly above the national figures among residents of the lowest income households, and significantly below the national level among people in the highest income households.  Similarly, a relatively high proportion of people with less than secondary graduation reported MUPS, while the proportion was lower among postsecondary graduates.  However, the relationship between educational attainment and the three individual conditions was less straightforward.

Compared with married people, those who were no longer married were almost twice as likely to report each of the three conditions.  This association with marital status remained significant when the effects of the other socio-demographic variables were accounted for.

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Dependency

Significantly high percentages of people with MUPS reported some degree of dependency (Chart 1).  More than a quarter (27%) of them needed help with instrumental activities of daily living such as preparing meals, doing everyday housework, getting to appointments and running errands; this compared with 7% of people without MUPS.  As well, 8% of individuals with MUPS reported that they needed assistance with personal activities of daily living such as bathing, dressing, eating, taking medication, and moving about inside the house; the figure was 2% among people who did not report MUPS.  Even when socio-demographic factors were taken into account, the association between MUPS and dependency remained significant (data not shown).

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Mental health and well-being

Not surprisingly, substantial proportions of people with MUPS had a negative perception of their physical health (data not shown).  They were also more likely than people who did not have MUPS to view their mental health as fair or poor: 15% versus 4%.  As well, close to one-quarter (23%) of people with MUPS were dissatisfied with their lives, compared with 8% of those who were not afflicted (Chart 2).

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Mental disorders

An extensive literature has shown MUPS to be strongly and consistently associated with psychosocial distress and psychiatric disorders.^6,9   According to the 2002 CCHS, individuals with MUPS were more likely than people without MUPS to have psychiatric disorders.  The analysis in this article focuses on the past 12-month prevalence of major depressive disorder, bipolar I disorder, panic disorder, social anxiety disorder, and agoraphobia.  Respondents who met the criteria for at least one of these five conditions were considered to have a mental disorder.

More than one-fifth (21%) of people with MUPS had at least one of these disorders, compared with 8% of those who did not have MUPS and 10% of people with other chronic physical conditions such as asthma, diabetes, migraine, cancer and heart disease (Table 2).  The prevalence of psychiatric disorders was particularly common among people with CFS:  36%.  But although the prevalence of mental disorders was high among people with MUPS, some research suggests that the stress of having unexplained symptoms may lead to mental health problems — in many cases, MUPS precedes psychiatric symptoms.¹²

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Consultations with health care providers

Patients with MUPS tend to report a relatively large number of medical consultations.  Compared with people without MUPS, and even with those who had other chronic conditions, individuals with MUPS were more likely to seek assistance from both conventional and alternative health care providers (Chart 3).  In 2003, 22% of MUPS patients reported having consulted their family doctor or general practitioner more than 10 times in the past year; 7% of people without MUPS had done so.  Over 40% of people with MUPS had consulted specialists versus 26% of those without MUPS.  And 32% of all MUPS patients sought help from alternative practitioners, compared with 20% of people without MUPS.  These high consultation rates, however, may reflect multiple referrals.