179Highly Correlated Symptoms
As previously noted , many of the symptoms experienced by FMS patients are inter-
correlated. Restless sleep, for instance, is linked to daytime fatigue and musculo-
skeletal pain, and thus sleep, fatigue, and pain scores all will be affected [ 48 ].
Depression and anxiety are independently associated with the severity of pain
symptoms in FMS [ 49 ]. In turn, depression is often associated with severe fatigue
and poor quality sleep, whereas anxiety is more commonly linked to palpitations,
dizziness, sweating, and paresthesia [ 24 ]. In addition, decreased cognitive function
seems to be related to pain severity in various chronic pain populations [ 26 ].
Concomitant Diseases
Very importantly, FM may occur concomitantly with other articular diseases, such
as lupus erythematosus, rheumatoid arthritis, and other systemic and chronic pain
syndromes. The effect of FMS in all of them has been widely studied [ 50 – 57 ]. The
opposite, however, that is the impact of other diseases on FMS has been less studied,
but it can be anticipated that the measures of pain, daily functioning, and even
fatigue will be clearly affected. Not only rheumatic diseases can appear concomi-
tantly, but also other diseases, such as multiple sclerosis, that present with fatigue or
other symptoms similar to those present in FMS may interfere with the disease
outcome measures reported by the patient, e.g., through PROMs [ 58 , 59 ]. The exis-
tence of concomitant diseases with similar symptoms may pose a double-sided
management decision: to escalate the treatment of the non-FMS condition (i.e., bio-
logical therapy in infl ammatory diseases) or to increase analgesia to treat FMS. A
better approach would be to use cognitive-behavioral therapy to approach both
conditions.
On the other hand, FMS is closely associated with other comorbid conditions.
Reported co-prevalence for some of these diseases varies from 25 to 67 % for osteo-
arthritis, 10 to 42 % for hypertension, 12 to 40 % for osteoporosis, and 4 to 23 % for
diabetes [ 60 – 62 ]. Not surprisingly, FMS is associated with other psychological dis-
orders. Earlier reports revealed that FMS patients are at a higher risk of dying from
suicide and accidents [ 63 , 64 ]. In view of the fact that FMS patients are rarely
admitted to hospital because of FM as the primary diagnosis, and that most, if not
all, of these associated disease processes are treatable and often can be managed
effectively on an outpatient basis, it is therefore important to take such symptoms
seriously and explore FMS patients for the risk of having other associated ailments
with views toward implementing effective prevention/management strategies.
7 PROMs for Fibromyalgia