Statistical analyses
Statistical analyses were performed using SPSS 25.0 (IBM Corp., Armonk,
NY, USA). In the univariate analyses, the chi-squared test was used to
compare categorical variables, while Student’s t-test was used for
continuous variables. Logistic regression analysis was used to assess
the risk factors for paranasal sinusitis. Additionally, the
Cochran–Armitage trend test of SAS 9.4 (SAS Institute, Cary, NC, USA)
was used to analyze the age-specific prevalence of paranasal sinusitis
in smokers and non-smokers. A p-value <0.05 was considered
statistically significant for all analyses.
Results
Among the 4813 participants who were investigated (2368 men and 2445
women; mean age, 53.1±10.1 years), paranasal sinusitis was diagnosed in
740 (15.4 %). Table 1 shows the characteristics of the study
participants with and without paranasal sinusitis. The data show that
sex was significantly associated with the presence of paranasal
sinusitis, together with age, BMI, alcohol consumption, stroke, smoking,
and hypertension.
Logistic regression analysis was performed to examine the risk factors
associated with paranasal sinusitis (Table 2). When adjusted for age and
sex (Model A), alcohol consumption and hypertension were not
significantly associated with paranasal
sinusitis.
The final model
(Model
B) adjusted for all the factors that
were
found to be statistically significant in the univariate analysis,
including age, sex, BMI, smoking, alcohol consumption, hypertension, and
stroke—only smoking was significantly associated with the prevalence
of paranasal sinusitis.
The
age-specific prevalence of paranasal sinusitis in smokers and
non-smokers is shown in Table 3. For all age groups, the prevalence was
higher in smokers than in non-smokers (Figure 1). The
prevalence
of paranasal sinusitis significantly increased with age in non-smoking
individuals, whereas no significant age-specific difference was found
among smokers (trend test, non-smokers p<0.001; smokers
p=0.499).
Table 4 shows a comparison of the prevalence of sinusitis affecting
different regions between smokers and non-smokers; the anterior nasal
sinuses were more often affected in smokers than in non-smokers, while
no significant difference was found regarding the sphenoid sinus. Among
the total study population, maxillary sinusitis was the most prevalent
(13.4 %) while the prevalence was 19.1 % in smokers and 11.7 % in
non-smokers.
Discussion
The present study investigated the prevalence of paranasal sinusitis,
diagnosed using MRI, among a community population from Shanghai, China.
Additionally, the epidemiological and clinical characteristics of
sinusitis between smokers and non-smokers were investigated. Overall,
the prevalence of
paranasal
sinusitis was found to be 15.4 % in adults aged 35–75 years. This
prevalence increased concurrently with age, from 12.6 % (35–44 years)
to 16.5 % (55–75 years); a peak was reached at 55 years, stabilizing
thereafter. The Cochran–Armitage trend test further showed that there
was a positive correlation between age and paranasal sinusitis in
non-smokers, while the prevalence in smokers remained consistently high,
at more than 20 % in each age group. Moreover, it was found that
paranasal sinusitis more often involved the anterior nasal sinuses in
smokers than in non-smokers.
In China, the first large-scale investigation concerning the
epidemiology of CRS was reported in 2015. This investigation estimated a
CRS prevalence of 8.0 % in the entire population and 8.2 % among
adults aged 15–75 years 21, which was lower than the
prevalence noted in the present study. This difference may be explained
as follows: The previous study diagnosed CRS based on the results from a
standardized questionnaire, whereas this study employed MRI for this
purpose. The former method of diagnosis may result in some patients with
unobvious
symptoms being overlooked, while the latter is not able to distinguish
the course or type of sinusitis effectively. Havas et al. reported
abnormal CT and MRI findings of the paranasal sinuses in asymptomatic
adults to be as high as 42.5 % 13. Kim et al. further
confirmed that the prevalence and risk factors of CRS differed rather
substantially when using different criteria, even in the same population22. Because of this difference, the investigation from
2015 may have underestimated the prevalence.
Compared to other studies that diagnosed paranasal sinusitis by means of
MRI, the prevalence noted in our study was lower than that noted in
studies
from Denmark (31.7 %) 20, Japan (33.8 %)23, and Norway (66 %) 12. We
believe that this variation could be due to the use of different
diagnostic criteria and research techniques. Additionally, the
prevalence of paranasal sinusitis is influenced by climate and race,
being more likely to occur in colder climates and in people who are
white 24-26. That said, in Japan, a Lund–Mackay score
≥4 was classified as an MRI abnormality that was suspected as sinusitis,
whereas in Norway, opacifications that indicated mucosal thickenings,
polyps, retention cysts, or fluid were recorded when measuring
>1 mm. In our study, however, mucosal thickening of ≥5 mm
was used as an indication of paranasal sinusitis, as per the Danish
diagnostic criteria. By choosing a relatively high cut-off value,
challenges regarding overdiagnosis due to the high sensitivity of MRI
can be overcome, ensuring more accurate findings 20.
Among all the participants in this study, 49.2 % were men. We found
that men were approximately 86 % more likely to have paranasal
sinusitis than women (adjusted OR = 1.86, 95 % CI = 1.54–2.24), which
is consistent with the results of studies from Asia 21,
23, 27. However, some surveys from developed Western countries found
that women were at a higher risk of developing paranasal sinusitis6, 9, 28. This discrepancy may be related to
differences in the living habits and level of awareness of paranasal
sinusitis between populations from Eastern and Western countries.
At present, the relationship between the prevalence of paranasal
sinusitis and age is somewhat controversial. In a previous study, Chen
et al. found that the prevalence of CRS in Canadians older than 12 years
increased with age, reaching a plateau after the age of 60 years28. Additionally, Hirsch et al. found that the
prevalence of CRS peaked at 15.9 % between the ages of 50 and 59 years,
subsequently dropping to 6.8 % after age 69 24, while
Shi et al. found a higher prevalence in individuals aged 15–34 years21. In our study, we found that the overall prevalence
of paranasal sinusitis in adults aged 35–75 years increased with age,
reaching a peak at 55 years of age and stabilizing thereafter. The
prevalence of paranasal sinusitis was found to have a strong positive
correlation with age, particularly among non-smokers. This may be
related to certain changes in the nasal anatomy and physiology that
occurs with aging, such as reduced mucosal blood flow and impaired
mucociliary function 29.
It is well known that smoking is closely related to respiratory
diseases. Literature shows that tobacco smoke can adversely affect
sinonasal mucociliary clearance, innate immune function, and olfactory
mucosal metaplasia 8. Several clinical studies have
confirmed that there is a correlation between smoking and paranasal
sinusitis in the Asian population 8, 10, 30. Our
research confirmed these findings, in that smoking is one of the
significant independent risk factors in the development of paranasal
sinusitis.
The
location of paranasal sinusitis differs depending on its etiology. In
contrast to the abundant literature regarding the correlation between
smoking and paranasal sinusitis, there are relatively few studies
assessing its most prevalent location. Interestingly, we found that in
smokers, paranasal sinusitis more commonly occurs in the anterior nasal
sinuses than in
non-smokers,
where it occurs most often in the maxillary sinus, followed by the
ethmoid, frontal, and sphenoid sinuses. In smokers, the most common
sites of sinusitis were found to be the maxillary sinus, followed by the
sphenoid, frontal, and ethmoid sinuses.
Kjaergaard
et al. demonstrated that smokers have lower nasal cavity volumes and
smaller minimum cross-sectional areas, achieve lower peak nasal
inspiratory flow rates, and have a lower decongestive capacity of the
nasal mucosa 31. Hence, we speculate that these nasal
changes brought about by smoking are more likely to affect the
mucociliary clearance movement and ventilation of the anterior nasal
sinuses that open in the middle nasal passage. More research is needed
to support this hypothesis.