Discussion
In the present study, the Association of DII score with obesity indexes
and sleep quality was assessed in Iranian female college students which
indicated no significant association between DII score and obesity.
However, a significant association was observed between the DII and PSQI
score.
Consistent with our findings, the study by Sen et al. did not show any
significant associations between DII and obesity (OR=1.4, 95% CI
-0.8-2.3, p=0.23).42 Moreover, the findings from the
SU.VI.MAX study with 3726 participants indicated no significant
association between WC and DII score (p=0.45).43 In
another cross-sectional survey among the Luxembourg population
(ORISCAV-LUX), no significant associations was observed in the
Association between DII score and WC, which was in line with our
findings.44 Moreover, a cross-sectional study among
464 police officers indicated that DII has no association with WC as a
Mets component.45 Sokol et al. showed a significant
association of DII with waist components only in males, not in
females.46 In contrast to our findings, in some other
research studies that were carried out in Iran,47 and
Spain (PREDIMED’ study and SUN cohort study),48,49 a
significant association between DII and obesity or Mets components were
detected. Lack of significant Association of the DII score with WC and
BMI in the present study may be related to the sample size, type of
research (cross-sectional), the numbers of food items in the calculation
of DII and a small mean of BMI compared to studies that have observed a
significant association. In the present study, a significant association
was observed between the DII and PSQI score. In the recent study by
Lopez et al., it was shown that the DII score was only positively
associated with daytime sleepiness as a component of PSQI (β=0.47, p
value<0.05).50 In the study by Godos et al.
participants in the highest quartile of DII score were more likely to
have a poor sleep (OR = 0.49, 95% CI: 0.31- 0.78). Moreover, the
authors demonstrated that high adherence to the Mediterranean diet as an
anti-inflammatory dietary pattern, could improve sleep quality in
Italian adults through the direct and indirect effects on health and
body weight status, respectively.51 Bilgic et al.
showed that increased malnutrition-inflammation score was significantly
associated with the presence of depression, sleep disorders, and poor
quality of life52.
The evidence from studies represented that that poor sleep was
associated with chronic, low-grade inflammation status. Short and long
sleep duration was associated with increased inflammation markers, and
sleep disruption may be related to diabetes via a mechanism of low-grade
systemic inflammation53. Several studies suggested
that a decrease in the number of hypocretin-containing neurons may be
caused by an inflammatory- or immune-mediated
process54-56. Hypocretin cell loss was observed in
most patients with sleep disorder narcolepsy54.
Gordon‑Dseagu et al. examined the Association between sleep variables
and 891 fasting plasma metabolites among the participants from the
Dietary Approaches to Stop Hypertension (DASH) trial. They observed that
sleep parameters was associated with metabolites and pathways which had
a relationship with inflammation and oxidative stress, including
erythrulose (advanced glycation end-product) (positive Association) and
several γ-glutamyl pathway metabolites, including CMPF (fatty acid,
dicarboxylate), isovalerate (valine, leucine and isoleucine and fatty
acid metabolism) and HWESASXX (polypeptide) (inverse
association).57 The mechanisms about the Association
between the DII score and health may be linked to the primary role of
several dietary components on systemic inflammatory pathways and gut
microbiota.58,59 It has been shown that low intake of
vegetables and unhealthy eating habits were associated with poor sleep
quality; vegetables are important sources of vitamins and polyphenols,
which can lead to reduce pro-inflammatory response and oxidative damage,
and represent neuroprotective effects.60 Omega 3 fatty
acids and MUFA have known as anti-inflammatory properties. It was found
in some studies regarding both Docosahexaenoic acid and the
Docosahexaenoic acid: Arachidonic acid ratio affected sleep quality and
inflammation61. In contrast, high intake of meat
products and refined carbohydrates have been related to an increase in
pro-inflammatory response.60 Regarding the influence
of the gut microbiota on inflammation, it could be stated that there was
a large data of various studies suggesting a mechanistic link between
gut-derived inflammatory response and neurodegeneration via the pathways
including modulation of plasma levels of lipopolysaccharide, the
inflammasome, type I interferon, and nuclear factor kappa B cells
(NF-KB).62 It should be noted that the present study’s
participants had less intake of foods impacting the availability of
tryptophan, and its conversion to serotonin and melatonin such as
protein and vitamins B group compared to global mean
intake.63