EFFECT OF MATTRESS FIRMNESS ON THE EVOLUTION OF PATIENTS WITH
BACK PROBLEMS
Title.
Evaluation of the effect of two kinds of
mattress on back pain. A controlled, randomized, and double
blinded clinical trial.
Background.
While there is a strong assumption among
the general public and even among the medical community that
the characteristics of the bed surface, and particularly their
firmness, can influence the emergence, intensity and/or recurrence
of pain associated with various kinds of mechanical pathologies
of the spine, currently there is no scientific evidence supporting
this assumption nor are there reliable data showing what kind
of rest surface is more appropriate for healthy subjects or
patients. In fact, very few studies of this matter have been
made and their poor methodology prevents one from extracting
reliable conclusions.
However, while it was not known what specific characteristics
had a specific effect, there was data suggesting that the
characteristics of the bed did have an appreciable effect.
The Foundation itself had promoted a wide epidemiological
study on the frequency of back problems among adolescents
and the factors associated with a greater risk of suffering
them (see page 11), and its results showed that the factor
associated with a greater risk, both among adolescents as
well as among their parents, was feeling discomfort in bed,
with a much stronger association than other factors, such
as having been diagnosed with scoliosis or uneven leg length.
For that reason, it was found necessary to study in greater
depth the influence of certain specific characteristics of
the sleeping surface on back problems, and in this specific
case, to define the effect the different mattress firmness
has on the evolution of pain in those who already have back
pain.
Objective.
To evaluate the effect of two different kinds
of mattress (one, very firm, the other medium firm) on the
evolution of pain in those people who already suffer back
pain during the night or upon waking.
Methodology.
It was a randomized, controlled and double
blind clinical trial. The study population was made up of
the adults (fathers and mothers, not the adolescents) who
participated as "cases" in the case and control
study on the risk associated with mattress characteristics
that are associated with a greater risk of suffering back
pain among the general public. Therefore, the entire study
sample suffered this kind of pain.
The sample of this study was recruited during that retrospective
study. The sample was made up of subjects who did not present
criteria for exclusion and who consented to participate in
a study that entails the need to change their mattress (free
of charge). To prevent the influence of one spouse over another,
only one subject per family unit was included (husband or
wife), even if both had back pain. However, the evolution
of the spouse eventually excluded was collected as a "side
effect".
The sample was randomly divided into two groups. The subjects
in one group were given very firm mattresses and those in
the other group, medium firm mattresses. The bed frames were
homogenized so that firm frames were provided, free of charge,
to those people who did not already have them.
Neither the patients, nor the technicians who installed the
mattresses in their homes, nor the physicians who evaluated
the patients' evolution, nor the statisticians who compared
that evolution in both groups knew to which specific group
each patient had been assigned.
The follow-up was 90-days and the main variables that were
controlled were: pain upon waking, measured by the visual
analog scale, and limitations on quality of life due to low
back pain, measured by the Spanish version of the Roland-Morris
disability scale. Additionally, exploratory variables were
collected, such as the evolution of the back pain in the spouse
from the moment the mattress was changed, medication use,
relation between the new mattress and the previous one, anthropometric
variables, mattress size, etc.
The statistical analysis compared the evolution of the variables
between the two groups. For deontological reasons, the subjects
who did not like the mattress assigned to them received, free
of charge, one of their own choice once they ceased to participate
in the study.
Participants, along with the Foundation's
Science Department.
Research Unit and Department of Rheumatological
Rehabilitation of the Ramón y Cajal Hospital. Department
of Neurosurgery of the Zarzuela Clinic and the Hospital Clínico
of Barcelona, and the Department of Morphological Sciences
at the Central University of Barcelona.
The study was co-funded by the Kovacs Foundation and Flex,
which contributed the mattresses evaluated in both groups.
Status.
The study was concluded and the corresponding
scientific article was published in Lancet 2003; 362:1599-1604.
Basically, its results show that the change in mattress influences
significantly the evolution of back pain but that, as opposed
to previously widely held assumptions, a medium firm mattress
improves more than double and double the number of patients
the pain and functional disability associated with back pain.
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