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the univariate analysis (OR = 0.72, 95% CI = 0.60–0.88,
p-value < 0.001) and in model 1 (OR = 0.64, 95%
CI = 0.52–0.78, p-value < 0.001). It also was associa-
ted with a reduced risk of severe knee OA in model 1
(OR = 0.59, 95% CI = 0.44–0.79, p-value < 0.001). Ho-
wever, the associations were not significant with knee
OA (OR = 0.82, 95% CI = 0.66–1.01, p-value = 0.059)
and severe knee OA (OR = 0.79, 95% CI = 0.58–1.06,
p-value = 0.117) in model 2.
DISCUSSION
This study utilized data from a nationwide survey to
assess the relationship between objectively defined
metabolic syndrome and knee OA. Additional ana-
lyses were performed to appraise the dose-response
relationship of the number of metabolic syndrome
components and the effect of individual metabolic syn-
drome components on knee OA. In women, metabolic
syndrome was associated with the development of knee
OA and severe knee OA. Furthermore, the number of
metabolic syndrome components was associated with
the development of OA. However, this relationship
was not established in men.
The prevalence of knee OA and severe knee OA
was higher in women with metabolic syndrome than
in men. This was consistent with previous studies that
reported an association between metabolic syndrome
components and development of knee OA. In a study
by Engström et al. based on a Western population, the
result showed that after adjusting for age, sex, smoking,
physical activity, and C-reactive protein, the presence
of metabolic syndrome was associated with a signifi-
cantly increased risk of knee OA (20). A study using
nationwide data reported that metabolic syndrome and
the development of knee OA showed no association
after adjusting for confounding factors, such as age
and sociographic factors of exercise, alcohol intake
and smoking (15). This, however, may be due to the
fact that diagnosis of knee OA was performed in a self-
reporting manner. The current study used radiological
findings to diagnose knee OA more accurately. In the
presence of metabolic syndrome, mechanical effects
of high body weight may influence the development
of knee OA (21). Recently, however, the emphasis has
been on the metabolic effects of metabolic syndrome.
Yusuf et al. reported that overweight is associated with
increased risk of OA in non-weight-bearing joints of
the hand (22). A meta-analysis showed that type 2
diabetes increased the risk of OA, after adjustment
for body weight (9). The results of the current study
in a nationwide representative population also support
the relationship between metabolic syndrome and OA
in women.
www.medicaljournals.se/jrm
To determine the dose-response relationship of me-
tabolic effects, we analysed the association between
the number of metabolic syndrome components and
development of knee OA or severe knee OA. In wo-
men, the risk of knee OA and severe knee OA tended
to increase as the number of metabolic syndrome
components increased. In a study by Yoshimura et al.
that showed similar results, 3 or more metabolic syn-
drome components in men, and 2 or more metabolic
syndrome components in women were associated
with increased risk of knee OA (23). However, the
fact that the study result was similar in both men and
women was in contrast with the results of our study,
which showed no significant relationship in men. The
difference between the 2 studies might be because of
the different study populations and diagnostic criteria
for knee OA.
The current study performed additional analyses on
the group with more severe knee OA. The reason was
that, in severe cases, knee OA is more symptomatic
and often requires special attention and more aggres-
sive treatment than less severe cases. The aim was
to elucidate the different impact that MS might have
on more severe cases of knee OA. In addition, unlike
the study by Yoshimura et al., we stratified the num-
ber of metabolic syndrome components from 0 to 5,
which helped to identify more detailed dose-response
relationships with metabolic syndrome components.
Contrary to our expectation, the risk of knee OA was
highest in patients with 4 metabolic syndrome compo-
nents, rather than with 5 components. Various factors,
such as general medical condition, individual lifestyle
or activity, may have influenced this finding. Further
study is needed to determine the exact mechanism.
However, in the aforementioned studies, including
our study, the different effect size of each component
was not considered. This was a limitation of these dose
response analyses.
In men, a significant relationship between metabolic
syndrome and knee OA was not definite. The presence
of metabolic syndrome was not associated with the
development of knee OA and severe knee OA. In ad-
dition, in a dose-response analysis, the risk of knee
OA only increased in men with 5 metabolic syndrome
components. As knee OA is more common in women,
who are more vulnerable to other risk factors for knee
OA, it can be assumed that women are more vulnerable
to metabolic risk factors for the development of knee
OA (4, 24). However, further basic research regarding
metabolic markers is needed to confirm the mechanism
of the different responses in men and women.
In a component analysis, abdominal obesity and
hypertension was generally associated with increased
the risk of knee OA and severe knee OA in both sexes.