Association between Fiber Intake and Risk of Incident Chronic Kidney Disease: The UK Biobank Study.

OBJECTIVES: Dietary fiber intake is associated with a lower risk of diabetes, cardiovascular disease, and cancer. However, it is unknown whether dietary fiber has a beneficial effect on preventing the development of chronic kidney disease (CKD). DESIGN, SETTING, PARTICIPANTS AND MEASUREMENTS: Using the UK Biobank prospective cohort, 110,412 participants who completed at least one dietary questionnaire and had an estimated glomerular filtration rate ≥60 mL/min/1.73 m2, urinary albumin-to-creatinine ratio <30 mg/g, and no history of CKD were included. The primary exposure was total dietary fiber density, calculated by dividing the absolute amount of daily total fiber intake by total energy intake (g/1,000 kcal). We separately examined soluble and insoluble fiber densities as additional predictors. The primary outcome was incident CKD based on diagnosis codes. RESULTS: A total of 3,507 (3.2%) participants developed incident CKD during a median follow-up of 9.9 years. In a multivariable cause-specific model, the adjusted hazard ratios (aHRs; 95% confidence intervals [CIs]) for incident CKD were 0.85 (0.77-0.94), 0.78 (0.70-0.86), and 0.76 (0.68-0.86), respectively, for the second, third, and highest quartiles of dietary fiber density (reference: lowest quartile). In a continuous model, the aHR for each +∆1.0g/1,000 kcal increase in dietary fiber density was 0.97 (95% CI, 0.95-0.99). This pattern of associations was similar for both soluble and insoluble fiber densities and did not differ across subgroups of sex, age, body mass index, hypertension, diabetes, smoking, and inflammation. CONCLUSION: Increased fiber intake was associated with a lower risk of CKD in this large well-characterized cohort.

Clinical effectiveness of house dust mite immunotherapy in mono- versus poly-sensitised patients with allergic rhinitis: a systematic review and meta-analysis.

Selecting an appropriate allergen-specific immunotherapy (AIT) regimen for polysensitised allergic rhinitis (AR) patients is challenging for clinicians. Although previous studies showed comparable effectiveness of single-allergen AIT with house dust mite (HDM) extract between monosensitised and polysensitised AR patients, there is no systematic review and meta-analysis demonstrating the comparable effectiveness of HDM AIT. In this meta-analysis, we analysed nine studies to compare the clinical effectiveness of HDM AIT. The primary outcome was nasal symptom score and secondary outcomes were medication and quality of life scores. The changes in nasal symptom score after HDM AIT did not significantly differ between monosensitised and polysensitised patients. The clinical effectiveness of HDM AIT regarding medication and quality of life score was not significantly different between monosensitised and polysensitised patients). In conclusion, single-allergen AIT with HDM extract showed comparable clinical effectiveness between polysensitised and monosensitised patients with AR.

Probiotic effects of mixture of Groenewaldozyma salmanticensis and Gluconacetobacter liquefaciens on growth and immune responses in Paralichthys olivaceus.

This study was performed to evaluate the effects of dietary probiotics on growth, non-specific immune responses and disease resistance in olive flounder, Paralichthys olivaceus. During 8 weeks, the fish were fed the five experimental diets such as a basal commercial diet (CON), oxytetracycline (OTC) and three basal diets containing Bacillus subtilis (BS), a commercial microbial product (CES) and a mixture of yeast and bacterium (PI), respectively. Fish fed all the probiotics diets and OTC showed a significantly higher growth than fish-fed CON (P < 0·05). Fish-fed PI had a significantly higher nitroblue tetrazolium activity, whereas fish-fed CES showed a higher lysozyme level (P < 0·05). A 7-day challenge test also showed that fish-fed PI had a cumulative survival rate equivalent to that of fish-fed OTC (P < 0·05). Moreover, the diet (PI) appeared to increase the diversity of microbial community in the fish. All these results suggest that the probiotics diet could function as a potential antibiotic replacer in the olive flounder. SIGNIFICANCE AND IMPACT OF THE STUDY: This study is unique in revealing that a diet mixture of yeast, Groenewaldozyma salmanticensis and bacterium Gluconacetobacter liquefaciens can enhance growth, innate immunity and diversity of microbial community including dominant species in the olive flounder. All these indicate that the diet mixture could function as a potential antibiotic replacer in one of the most commercially important fisheries in South Korea.

Chronic hyponatremia and association with osteoporosis among a large racially/ethnically diverse population.

Chronic hyponatremia may contribute to decreased bone density. We studied 341,003 men and women who underwent DXA testing and observed that individuals with chronic hyponatremia (sodium < 135 mEq/L) had an 11% greater likelihood of having osteoporosis. There was a dose-dependent effect with lower sodium and stronger association with osteoporosis. INTRODUCTION: Chronic hyponatremia has been associated with both neurologic deficits and increased risk of gait abnormalities leading to falls and resultant bone fractures. Whether chronic hyponatremia contributes to decreased bone density is uncertain. We evaluated whether chronic, mild hyponatremia based on serial sodium measurements was associated with increased risk of osteoporosis within a large, ethnically diverse population. METHODS: This is a retrospective cohort study between January 1, 1998 and December 31, 2014 within Kaiser Permanente Southern California, an integrated healthcare delivery system. Men and women were aged ≥ 55 years with ≥ 2 serum sodium measurements prior to dual-energy X-ray absorptiometry (DXA) testing. Time-weighted (TW) mean sodium values were calculated by using the proportion of time (weight) elapsed between sodium measurements and defined as < 135 mEq/L. Osteoporosis defined as any T-score value ≤ - 2.5 of lumbar spine, femoral neck, or hip. RESULTS: Among 341,003 individuals with 3,330,903 sodium measurements, 11,539 (3.4%) had chronic hyponatremia and 151,505 (44.4%) had osteoporosis. Chronic hyponatremic individuals had an osteoporosis RR (95% CI) of 1.11 (1.09, 1.13) compared to those with normonatremia. A TW mean sodium increase of 3 mEq/L was associated with a lower risk of osteoporosis [adjusted RR (95% CI) 0.95 (0.93, 0.96)]. A similar association was observed when the arithmetic mean sodium value was used for comparison. CONCLUSIONS: We observed a modest increase in risk for osteoporosis in people with chronic hyponatremia. There was also a graded association between higher TW mean sodium values and lower risk of osteoporosis. Our findings underscore the premise that chronic hyponatremia may lead to adverse physiological effects and responses which deserves better understanding.

Type III interferons are critical host factors that determine susceptibility to Influenza A viral infection in allergic nasal mucosa.

BACKGROUND: Allergic respiratory conditions have been associated with increased susceptibility to viral infection due to impaired interferon (IFN)-related immune responses, but the mechanisms for reinforcement of mucosal immunity against viral infection in allergic diseases are largely unknown. OBJECTIVES: To determine whether IFN induction would be impaired in allergic nasal mucosa and to identify whether higher loads of influenza A virus (IAV) in allergic nasal mucosa could be controlled with IFN treatment. METHODS: Influenza A virus mRNA, viral titres and IFN expression were compared in IAV-infected normal human nasal epithelial (NHNE, N = 10) and allergic rhinitis nasal epithelial (ARNE, N = 10) cells. We used in vivo model of allergic rhinitis (BALB/c mice, N = 10) and human nasal mucosa from healthy volunteers (N = 72) and allergic rhinitis patients (N = 29) to assess the induction of IFNs after IAV infection. RESULTS: Influenza A virus mRNA levels and viral titres were significantly higher in ARNE compared with NHNE cells. IFN-ß and IFN-λs were induced in NHNE and ARNE cells up to 3 days after IAV infection. Interestingly, induction of IFN-λs mRNA levels and the amount of secreted proteins were considerably lower in ARNE cells. The mean IFN-λs mRNA level was also significantly lower in the nasal mucosa of AR patients, and we found that recombinant IFN-λ treatment attenuated viral mRNA levels and viral titres in IAV-infected ARNE cells. In vivoAR mouse exhibited higher viral load after IAV infection, but intranasal inoculation of IFN-λ completely decreased IAV protein expression and viral titre in nasal mucosa of IAV-infected AR mouse. CONCLUSION: Higher susceptibility of the allergic nasal mucosa to IAV may depend on impairment of type III IFN induction, and type III IFN is a key mechanistic link between higher viral loads and control of IAV infection in allergic nasal mucosa.

Occupational exposure and idiopathic pulmonary fibrosis: a multicentre case-control study in Korea.

SETTING: Multicentred hospital-based cases and control subjects in Korea. OBJECTIVE: To evaluate the association between idiopathic pulmonary fibrosis (IPF) and hazardous materials to which people are occupationally exposed. DESIGN: A multicentre, hospital-based, matched case-control study was performed. The ratio of IPF cases to controls was 1:1 (n = 78 in each group). IPF cases and controls were matched in terms of age group, sex and place of residence. Conditional logistic regression analysis was performed. RESULTS: In simple logistic regression analysis, exposure to metal dust and any exposure for >1 year in an occupational setting were significantly associated with IPF (metal dust OR 4.00, 95%CI 1.34-11.97; any exposure OR 3.67, 95%CI 1.02-13.14). After adjustment for environmental and military exposures and smoking history, the OR for metal dust exposure was 4.97 (95%CI 1.36-18.17) in multiple logistic regression analysis. CONCLUSIONS: Metal dust was associated with incident IPF in Seoul and Gyeonggi Provinces in Korea. This information will be used to support a tailored preventive strategy in specific industries or occupations.

Incidence and prevalence of idiopathic interstitial pneumonia and idiopathic pulmonary fibrosis in Korea.

SETTING: Although the incidence and prevalence of idiopathic interstitial pneumonia (IIP) and idiopathic pulmonary fibrosis (IPF) have been assessed in Western countries, their epidemiology has not been analysed in Asian countries, including the Republic of Korea. OBJECTIVE: To estimate the prevalence and incidence of IIP, including IPF, in Korea, using a large, nationwide database. DESIGN: The Health Insurance Review and Assessment Services claims database, which includes information on every patient with diagnostic codes for IPF and IIP from 2010 to 2013, was reviewed. Age- and sex-specific IPF and IIP prevalence and incidence rates were estimated. RESULTS: Among Korean males and females, IPF prevalence from 2010 to 2013 was estimated at respectively 39.7 and 24.3 per 100 000 population, while IIP prevalence was estimated at respectively 97.1 and 66.5/100 000. The annual incidence rates among Korean males and females during 2011 and 2012 were respectively 16.4 and 9.7/100 000, for IPF, and respectively 42.3 and 27.5/100 000 for IIP. CONCLUSIONS: IPF is more prevalent in Korea than previously reported; its prevalence may be similar to or higher than in the United States and in European countries.

Effect of roflumilast on airway remodelling in a murine model of chronic asthma.

BACKGROUND: Airway remodelling is associated with irreversible, or partially reversible, airflow obstruction and ultimately unresponsiveness to asthma therapies such as corticosteroids. Roflumilast is a selective phosphodiesterase-4 inhibitor that has an anti-inflammatory effect in chronic obstructive pulmonary disease (COPD). OBJECTIVE: The objective of this study was to study the effect of roflumilast on airway inflammation and remodelling in a murine model of chronic asthma. METHODS: BALB/c mice sensitized to ovalbumin (OVA) were chronically exposed to intranasal OVA administration twice a week for additional 3 months. Roflumilast was administered orally during the intranasal OVA challenge. A lung fibroblast cell line was used in the proliferation assay. RESULTS: Compared with control mice, mice chronically exposed to OVA developed eosinophilic airway inflammation, airway hyper-responsiveness (AHR), and exhibited features of airway remodelling. Administration of roflumilast significantly inhibited airway inflammation and AHR. Roflumilast also significantly decreased goblet cell hyperplasia and pulmonary fibrosis, which are parameters of airway remodelling. The levels of interleukin (IL)-4, IL-5, and IL-13 in the bronchoalveolar lavage (BAL) fluids were significantly lower in the roflumilast group. In vitro, roflumilast significantly inhibited stem cell factor (SCF)-induced cell proliferation of fibroblasts. The SCF concentration and mRNA expression in a murine model also significantly decreased with roflumilast treatment. CONCLUSIONS: These results suggest that the administration of roflumilast regulates airway inflammation, AHR, and airway remodelling in a model of chronic asthma. The beneficial effects from roflumilast may be related to the SCF/c-kit pathway.

Risk factors for lung function impairment among the general non-smoking Korean population.

SETTING: Nationwide general population in South Korea. OBJECTIVE: Except for tobacco smoking, risk factors for the impairment of lung function have not been widely evaluated. We evaluated the risk factors for lung function impairment among the general non-smoking Korean population. DESIGN: A total of 8164 non-smokers from the spirometry data set of the Korean National Health and Nutrition Examination Surveys IV and V (2008-2010) were included in the study. After sex stratification, multiple survey logistic regression analyses were performed to estimate the association between potential risk factors and impaired lung function in this nationwide cross-sectional study. RESULTS: The proportion of non-smokers among the general Korean population with forced expiratory volume in 1 s (FEV1) < 80% of predicted, forced vital capacity (FVC) < 80% of predicted and FEV1/FVC ratio < 0.7 were respectively 46.2%, 50.3% and 30.2%. In multiple survey logistic regression analyses, lung function impairment was associated with tuberculosis (TB) and asthma in female non-smokers and asthma in male non-smokers. CONCLUSIONS: TB and asthma are risk factors for lung function impairment among Korean non-smokers. To prevent further lung function impairment, a careful control system for these factors should be considered when setting health policy priorities.

3D CFD simulations of trailing suction hopper dredger plume mixing: comparison with field measurements.

A 3D computational fluid dynamics (CFD) model is used to simulate mixing of an overflow plume within 400 m from a trailing suction hopper dredger (TSHD). The simulations are compared with new field measurements. It is the first time simulations of overflow dredging plumes are compared in such detail to field measurements this close to a TSHD. Seven cases with a large variety in overflow flux and plume characteristics are used. Measured maximum suspended sediment concentrations (SSC) vary between 30 and 500 mg/l and fluxes vary between 0.7% and 20% of the total overflow flux; the CFD model has, subject to the limitations of the field data, been shown to reproduce this in a satisfactory way. The model gives better understanding of important near field processes, which helps to assess the frequency, duration and intensity of stresses like turbidity and sedimentation needed to find the environmental impact of dredging projects.

3D CFD simulations of trailing suction hopper dredger plume mixing: a parameter study of near-field conditions influencing the suspended sediment source flux.

Frequency, duration and intensity of stresses like turbidity and sedimentation caused by dredging must be known to determine the environmental impact of dredging projects. These stresses depend on the amount of sediment spill from a dredger and on how much of this spill still is in suspension near environmentally sensitive areas. Near-field mixing close to a dredger influences the deposition behaviour of the sediment spill. This is investigated systematically with computational fluid dynamics simulations for 136 different conditions of trailing suction hopper dredger overflow sediment plume mixing. Most important influences are found for the ambient depth and the crossflow velocity (vector sum of the dredging speed and the ambient velocity), which can result in a completely different suspended sediment source flux behind the dredger. The simulation results are translated into mathematical relations to predict the suspended sediment source flux without computational effort.

The ontogeny of cerebrovascular pressure autoregulation in premature infants.

OBJECTIVE: To quantify cerebrovascular autoregulation as a function of gestational age (GA) and across the phases of the cardiac cycle. STUDY DESIGN: The present study is a hypothesis-generating re-analysis of previously published data. Premature infants (n=179) with a GA range of 23 to 33 weeks were monitored with umbilical artery catheters and transcranial Doppler insonation of the middle cerebral artery for 1-h sessions over the first week of life. Autoregulation was quantified by three methods, as a moving correlation coefficient between: (1) systolic arterial blood pressure (ABP) and systolic cerebral blood flow (CBF) velocity (Sx); (2) mean ABP and mean CBF velocity (Mx); and (3) diastolic ABP and diastolic CBF velocity (Dx). Comparisons of individual and cohort cerebrovascular pressure autoregulation were made across GA for each aspect of the cardiac cycle. RESULTS: Systolic, mean and diastolic ABP increased with GA (r=0.3, 0.4 and 0.4; P<0.0001). Systolic CBF velocity was pressure-passive in infants with the lowest GA, and Sx decreased with advancing GA (r=-0.3; P<0.001), indicating increased capacity for cerebral autoregulation during systole during development. By contrast, Dx was elevated, indicating dysautoregulation, in all subjects and showed minimal change with advancing GA (r=-0.06; P=0.05). Multivariate analysis confirmed that both GA (P<0.001) and 'effective cerebral perfusion pressure' (ABP minus critical closing pressure (CrCP); P<0.01) were associated with Sx. CONCLUSION: Premature infants have low and usually pressure-passive diastolic CBF velocity. By contrast, the regulation of systolic CBF velocity by pressure autoregulation developed in this cohort between 23 and 33 weeks GA. Elevated effective cerebral perfusion pressure derived from the CrCP was associated with dysautoregulation.

Health care use and economic burden of patients with diagnosed chronic obstructive pulmonary disease in Korea.

BACKGROUND: The prevalence and economic burden of chronic obstructive pulmonary disease (COPD) are increasing worldwide. However, little information is available concerning COPD-associated health care use and costs in Korea. OBJECTIVE: To analyse 1) health care use, medical costs and medication use in 2009, and 2) changes in costs and medication use over 5 years (2006-2010). DESIGN: Using the database of the Korean Health Insurance Review and Assessment Service, COPD patients were identified by searching on both ICD-10 codes and COPD medication. RESULTS A total of 192,496 COPD patients were identified in 2009. Total medical costs per person were US$2803 ± 3865; the average annual number of days of out-patient care and days of hospitalisation were respectively 40 ± 36 and 11 ± 33. Methylxanthine and systemic beta-agonists were the most frequently used drugs. However, the number of prescriptions for long-acting muscarinic antagonist increased rapidly. The total cost of COPD-related medications increased by 33.1% over 5 years. CONCLUSION: The present study provides new insight into health care use and the economic burden of COPD in Korea. Changing patterns of COPD-related medication use could help inform COPD management policies.

Clinical characteristics and prognosis of pneumonia and sepsis: multicenter study.

BACKGROUND: Pneumonia is the primary source of sepsis and is significantly associated with mortality. However, only a few studies focus on its clinical characteristics and outcomes. METHODS: We evaluated 500 intensive care unit patients who met severe sepsis or septic shock criteria, dividing them into two distinct groups (43%, sepsis with pneumonia; 41%, sepsis with an infection other than pneumonia). RESULTS: Moderate differences between the groups were observed. The group of sepsis with pneumonia had a higher 28-day in-hospital mortality (41% vs. 30%; P=0.02). Multivariate analysis revealed that the presence of pneumonia associated significantly with mortality (OR 1.76, 95% CI 1.11-2.78) along with cardiopulmonary resuscitation (OR 4.20, 95% CI 1.50-11.74), serum lactate ≥ 3.5 mmol/L (OR 1.92, 95% CI 1.20-3.08), and SOFA score ≥ 12 (OR 2.41, 95% CI 1.52-3.82). Survival analysis revealed for both groups that the patients with PaO2/FiO2 (PF) ratio <170 and lactate ≥ 3.5 mmol/L had a worse prognosis than the patients with PF ratio ≥ 170 and lactate ≥ 3.5 mmol/L or PF ratio <170 and lactate <3.5 mmol/L. CONCLUSION: In patients admitted with sepsis, the pneumonia infection independently predicts 28-day in-hospital mortality. Combining the levels of serum lactate and PF ratio could be a useful approach in predicting mortality of these patients.

Resveratrol prevents development of eosinophilic rhinosinusitis with nasal polyps in a mouse model.

BACKGROUND: Since the recent establishment of a murine model of eosinophilic chronic rhinosinusitis with nasal polyps (CRSwNP), both the development of new drugs for treatment or prevention of eosinophilic CRSwNP and elucidation of their pathogenesis have been feasible. We investigated the therapeutic effects of resveratrol on CRSwNP and its mechanism of action using a murine model. METHODS: After induction of eosinophilic CRSwNP, the therapeutic effects of resveratrol were tested and compared with those of triamcinolone acetonide. Histopathologic changes were evaluated using hematoxylin and eosin for overall inflammation, Sirius red for eosinophils, and Masson's trichrome stain for collagen. The expression levels of the interleukin (IL)-4, IL-5, prostaglandin D synthase, and leukotriene C4 synthase genes were assessed by quantitative real-time PCR. Cyclooxygense-2 and 5-lipoxygense levels were evaluated by immunohistochemical staining and Western blot analysis. RESULTS: The degree of eosinophilic infiltration and subepithelial fibrosis was significantly decreased by administration of high-dose resveratrol, the potency of which was similar to that of triamcinolone acetonide. The expression levels of the IL-4, IL-5, prostaglandin D synthase, and leukotriene C4 synthase genes were significantly decreased by administration of low- or high-dose resveratrol. The production of 5-lipoxygenase was strongly inhibited by high-dose resveratrol. CONCLUSIONS: Resveratrol may be useful for the prevention of eosinophilic CRSwNP. A key mechanism of its action is believed to be its anti-inflammatory effect, particularly on eosinophils, by inhibiting the lipoxygenase pathway.

Clinical characteristics of patients with tuberculosis-destroyed lung.

SETTING: Multicentre study. OBJECTIVE: To define the clinical characteristics of patients with tuberculosis (TB) destroyed lung due to past TB. DESIGN: We reviewed patients with TB-destroyed lung between May 2005 and June 2011. RESULTS: A total of 595 patients from 21 hospitals were enrolled. The mean age was 65.63 ± 0.47 (mean ± standard error); 60.5% were male. The mean number of lobes involved was 2.59 ± 0.05. Pleural thickening was observed in 54.1% of the patients. Mean forced vital capacity (FVC), forced expiratory volume in 1 s (FEV(1)), FEV(1)/FVC, bronchodilator response and number of exacerbations per year were respectively 2.06 ± 0.03 l (61.26% ± 0.79), 1.16 ± 0.02 l (49.05% ± 0.84), 58.03% ± 0.70, 5.70% ± 0.34, and 0.40 ± 0.04. The number of lobes involved was significantly correlated with FVC and FEV(1), and with the number of exacerbations per year. Use of long-acting muscarinic antagonists or long-acting beta-2 agonists plus inhaled corticosteroids resulted in bronchodilatory effects. Multivariable regression analysis showed that age, initial FEV(1) (%) and number of exacerbations during follow-up were independent factors affecting change in FEV(1). CONCLUSION: Decreased lung function with exacerbation, and progressive decline of FEV(1) were observed in patients with TB-destroyed lung.

Use of bisphosphonate and risk of atrial fibrillation in older women with osteoporosis.

UNLABELLED: Concerns have been raised among clinicians and patients whether or not bisphosphonates increase the risk of atrial fibrillation. In this large cohort study, increased risk of atrial fibrillation was not found to be associated with bisphosphonate. In fact, bisphosphonate even showed a protective effect against cardiac arrhythmia compared to other osteoporosis medications. INTRODUCTION: Increased risk of atrial fibrillation among bisphosphonate users has been reported; however, the results from these studies are controversial. The purpose of this study was to evaluate the risk of atrial fibrillation associated with bisphosphonate use in older women. METHODS: We used the Korean Health Insurance Review and Assessment Service claims database from May 1, 2005 to June 30, 2006. Retrospective cohort analysis was conducted on women 65 years or older with newly diagnosed cases of osteoporosis (ICD 10 code: M80, M81) who had not previously taken any medications for osteoporosis. Bisphosphonate-exposed and non-exposed patients were followed until they were either diagnosed with atrial fibrillation (ICD 10 code: I48) or until the end of the study. The Cox proportional hazards model was used to calculate hazard ratios and the 95% confidence intervals. RESULTS: Atrial fibrillation was reported in 626 of the 120,319 patients (0.52%) treated with bisphosphonates and 66 of 9,863 patients (0.67%) treated with other osteoporosis medications. Overall hazard ratio for developing atrial fibrillation in the bisphosphonate-treated group was 0.52 (95% CIs, 0.29-0.91). In patients with a medication possession ratio greater than 0.7, the hazard ratio was lower (HR 0.41, 95% CIs 0.23-0.75). In the subgroup analysis, alendronate showed a statistically significant protective effect against the risk of atrial fibrillation with a hazard ratio of 0.75 (95% CI, 0.58-0.97). CONCLUSION: Among older Korean women with osteoporosis, bisphosphonate was found to have a protective effect against atrial fibrillation.

Characteristics and risk factors of mucosal cysts in the paranasal sinuses.

BACKGROUND: Though mucosal cysts in the paranasal sinuses (PSMCs) are common findings on radiographic images, the nature of PSMCs and risk factors for the development of PSMCs have not yet been determined. The aim of this study was to evaluate the characteristics of PSMCs using brain magnetic resonance (MR) imaging. METHODOLOGY/PRINCIPAL: A total of 6831 subjects who underwent health checkup including brain MR imaging were included in this study. The characteristics of PSMCs, including their location, number and size, as well as the presence of obstruction of the sinus ostium and sinusitis, were analysed using brain MR images. Structured questionnaires and medical records were reviewed to evaluate the smoking status and comorbid medical conditions. RESULTS: The overall prevalence of PSMCs was 7.4% and was significantly higher in females than in males. PSMCs were most commonly found in the maxillary sinus, most of which were located unilaterally as a solitary cyst. Large cysts were associated with obstruction of the sinus ostium and subsequent sinusitis. Smoking was a single important risk factor for developing PSMCs. No significant associations were found between symptoms (nasal/respiratory) and the presence of PSMCs. CONCLUSIONS: The prevalence of PSMCs was 7.4% and decreased with age. Large cysts may lead to obstruction of the sinus and subsequent sinusitis. Smoking was an important risk factor for PSMCs, and the total amount of smoking correlated with cyst size. Most subjects were asymptomatic, and specific treatment was not performed.