Interaction of general obesity and abdominal obesity with frailty in patients with chronic kidney disease: a nationally representative analysis.

Background: General and abdominal obesity are prevalent, with established associations to frailty in the elderly. However, few studies have investigated these associations in patients with chronic kidney disease (CKD), yielding inconsistent results. Methods: This cross-sectional study analysed data from the National Health and Nutrition Examination Survey (NHANES 2003-2018). Frailty was evaluated by the 36-item frailty index. General obesity was defined as a body mass index (BMI) >30 kg/m2; abdominal obesity was identified if waist circumference (WC) reached 102 cm in men and 88 cm in women. The associations of general and abdominal obesity with frailty were analysed using weighted multivariate logistic regression and restricted cubic splines. The interaction of general and abdominal obesity with frailty was examined. Results: A total of 5604 adult patients (median age 71 years, 42% men) with CKD were included in this analysis, with a median estimated glomerular filtration rate of 57.3 ml/min/1.73 m2. A total of 21% were frail with general obesity and 32% were frail with abdominal obesity. Neither general nor abdominal obesity alone was associated with frailty. There was an interaction between general and abdominal obesity with frailty. Compared with individuals with normal BMI and WC, those with both general and abdominal obesity, rather than either alone, exhibited significantly increased odds of frailty {odds ratio [OR] 1.53 [95% confidence interval (CI) 1.20-1.95]}. General obesity was associated with being frail only when CKD patients had abdominal obesity [OR 1.59 (95% CI 1.08-2.36)]. Conclusions: There may be an interaction between general and abdominal obesity with frailty in patients with CKD. Interventions aimed at preventing frailty should consider both aspects.

Prevalence and associated factors of frailty in patients with chronic kidney disease: a cross-sectional analysis of PEAKING study.

AIM:  Frailty is common and is reported to be associated with adverse outcomes in patients with chronic diseases in Western countries. However, the prevalence of frailty remains unclear in individuals with chronic kidney disease (CKD) in China. We examined the prevalence of frailty and factors associated with frailty in patients with CKD. METHODS:  This was a cross-sectional analysis of 177 adult patients (mean age 54 ± 15 years, 52% men) with CKD from the open cohort entitled Physical Evaluation and Adverse outcomes for patients with chronic Kidney disease IN Guangdong (PEAKING). Frailty at baseline were assessed by FRAIL scale which included five items: fatigue, resistance, ambulation, illnesses, and loss of weight. Potential risk factors of frailty including age, sex, body mass index, and daily step counts recorded by ActiGraph GT3X + accelerometer were analyzed by multivariate logistic regression analysis. RESULTS: The prevalence of prefrailty and frailty was 50.0% and 11.9% in patients with stages 4-5 CKD, 29.6% and 9.3% in stage 3, and 32.1% and 0 in stages 1-2. In the multivariate logistic regression analysis, an increase of 100 steps per day (OR = 0.95, 95% CI 0.91-0.99, P = 0.01) and an increase of 5 units eGFR (OR = 0.82, 95% CI 0.68-0.99, P = 0.045) were inversely associated with being frail; higher BMI was associated with a higher likelihood of being frail (OR = 1.52, 95% CI 1.11-2.06, P = 0.008) and prefrail (OR = 1.25, 95% CI 1.10-1.42, P = 0.001). CONCLUSION:  Frailty and prefrailty were common in patients with advanced CKD. A lower number of steps per day, lower eGFR, and a higher BMI were associated with frailty in this population.

Rituximab biosimilar HLX01 versus reference rituximab in the treatment of diffuse large B-cell lymphoma: Real-world clinical experience.

INTRODUCTION: HLX01 is the first rituximab biosimilar produced in China and the first monoclonal antibody biosimilar marketed in China. The purpose of this study was to comprehensively evaluate whether HLX01 is clinically consistent with the original drug based on real-world data to provide evidence for the clinical substitution of biosimilars in China. METHODS: A single-center retrospective study was conducted to select patients with diffuse large B-cell lymphoma who met the inclusion criteria and were treated with HLX01 or reference rituximab. Baseline characteristics, efficacy and safety results were recorded, and the corresponding statistical analysis was performed for various indicators. RESULTS: Thirty-three patients diagnosed with diffuse large B-cell lymphoma were included and divided into two groups that received HLX01 or reference rituximab. The results showed no significant difference in the overall response rate (86.7% vs. 88.9%; p = 1.000) or complete response rate (46.7% vs. 55.6%; p = 0.889) between the two groups. Kaplan-Meier survival curves also showed no significant difference in time-to-event variables between the two groups (log-rank = 0.244). Safety was also comparable in both groups. CONCLUSIONS: HLX01 is a suitable replacement for reference rituximab in the treatment of diffuse large B-cell lymphoma and is relatively inexpensive, thereby reducing the economic burden of patients. Nevertheless, the conclusion of this study still needs to be further validated by large-sample real-world data and explored for HLX01 in other indications, such as follicular lymphoma. CLINICAL TRIAL REGISTRATION: Not applicable.

Fiber intake and health in people with chronic kidney disease.

Emerging evidence suggests that diet, particularly one that is rich in dietary fiber, may prevent the progression of chronic kidney disease (CKD) and its associated complications in people with established CKD. This narrative review summarizes the current evidence and discusses the opportunities for increasing fiber intake in people with CKD to improve health and reduce disease complications. A higher consumption of fiber exerts multiple health benefits, such as increasing stool output, promoting the growth of beneficial microbiota, improving the gut barrier and decreasing inflammation, as well decreasing uremic toxin production. Despite this, the majority of people with CKD consume less than the recommended dietary fiber intake, which may be due in part to the competing dietary potassium concern. Based on existing evidence, we see benefits from adopting a higher intake of fiber-rich food, and recommend cooperation with the dietitian to ensure an adequate diet plan. We also identify knowledge gaps for future research and suggest means to improve patient adherence to a high-fiber diet.

Evaluation of favipiravir in the treatment of COVID-19 based on the real-world.

BACKGROUND: The role of favipiravir (FVP) as a COVID-19 treatment is recognized but not fully elucidated. We aimed to evaluate whether FVP has definite clinical efficacy and safety in the treatment of COVID-19. METHODS: International and Chinese databases were searched for randomized controlled clinical trials evaluating FVP for the treatment of COVID-19. A meta-analysis was performed and published literature was synthesized to evaluate the corresponding therapeutic effects. RESULTS: We included 13 studies (1430 patients in total). Meta-analysis showed that patients with mild-to-moderate disease treated with FVP had a significantly higher viral clearance rate than those in the control group 10 and 14 days after initiation of treatment [RR: 1.13 (95% CI: 1.00, 1.28), P = 0.04; I2 = 39% for day 10 and RR: 1.16 (95% CI: 1.04, 1.30), P = 0.008; I2 = 38% for day 14] and a significantly shorter hospital stay [MD: -1.52 (95% CI: -2.82, -0.23), P = 0.02; I2 = 0%]. CONCLUSIONS: FVP significantly promotes viral clearance and reduces the hospitalization duration in mild-to-moderate COVID-19 patients, which can reduce the risk of severe disease outcomes in patients. However, more importantly, the results showed no benefit of FVP in severe patients, and caution should be taken regarding the treatment options of FVP in severe patients.

PLAIN LANGUAGE SUMMARYThe urgent need to identify effective interventions to treat novel coronavirus infections is a major challenge. The role of favipiravir (FVP) as a COVID-19 treatment is recognized but not fully elucidated. Our study showed a significant correlation between viral clearance and the promotion of clinical improvement with FVP in mild-to-moderate patients, which is significant for reducing the length of hospital stay of patients, reducing the risk of patients progressing to severe disease, thereby reducing mortality. However, the results showed no benefit of FVP in severe patients and the conclusion of this study still needs to be further verified by clinical trials with large samples.

Dihydroartemisinin improves hypercholesterolemia in ovariectomized mice via enhancing vectorial transport of cholesterol and bile acids from blood to bile.

The increase of concentrations of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) in the serum of postmenopausal women is the important risk factor of the high morbidity of cardiovascular diseases of old women worldwide. To test the anti-hypercholesterolemia function of dihydroartemisinin (DHA) in postmenopausal women, ovariectomized (OVX) mice were generated, and DHA were administrated to OVX mice for 4 weeks. The blood and liver tissues were collected for biochemical and histological tests respectively. The mRNA and protein expression levels of genes related to metabolism and transport of cholesterol, bile acid and fatty acid in the liver or ileum were checked through qPCR and western blot. DHA could significantly reduce the high concentrations of TC and LDL-C in the serum and the lipid accumulation in the liver of ovariectomized mice. The expression of ABCG5/8 was reduced in liver of OVX mice, and DHA could up-regulate the expression of them. Genes of transport proteins for bile salt transport from blood to bile, including Slc10a1, Slco1b2 and Abcb11, were also significantly up-regulated by DHA. DHA also down-regulated the expression of Slc10a2 in the ileum of OVX mice to reduce the absorption of bile salts. Genes required for fatty acid synthesis and uptake, such as Fasn and CD36, were reduced in the liver of OVX mice, and DHA administration could significantly up-regulate the expression of them. These results demonstrated that DHA could improve hypercholesterolemia in OVX mice through enhancing the vectorial transport of cholesterol and bile acid from blood to bile.

Ovariectomy Impaired Hepatic Glucose and Lipid Homeostasis and Altered the Gut Microbiota in Mice With Different Diets.

The lower incidence of metabolic diseases of women than men and the increasing morbidity of metabolic disorders of menopausal women indicated that hormones produced by ovaries may affect homeostasis of glucose and lipid metabolism, but the underlying mechanisms remain unclear. To explore the functions of ovaries on regulating glucose and lipid metabolism in females, 8 weeks old C57BL/6 mice were preformed ovariectomy and administrated with normal food diet (NFD) or high fat diet (HFD). Six weeks after ovariectomy, blood biochemical indexes were tested and the morphology and histology of livers were checked. The expression levels of genes related to glucose and lipid metabolism in liver were detected through transcriptome analysis, qPCR and western blot assays. 16S rDNA sequence was conducted to analyze the gut microbiota of mice with ovariectomy and different diets. The serum total cholesterol (TC) was significantly increased in ovariectomized (OVX) mice fed with NFD (OVXN), and serum low density lipoprotein-cholesterol (LDL-C) was significantly increased in both OVXN mice and OVX mice fed with HFD (OVXH). The excessive glycogen storage was found in livers of 37.5% mice from OVXN group, and lipid accumulation was detected in livers of the other 62.5% OVXN mice. The OVXN group was further divided into OVXN-Gly and OVXN-TG subgroups depending on histological results of the liver. Lipid drops in livers of OVXH mice were more and larger than other groups. The expression level of genes related with lipogenesis was significantly increased and the expression level of genes related with ß-oxidation was significantly downregulated in the liver of OVXN mice. Ovariectomy also caused the dysbiosis of intestinal flora of OVXN and OVXH mice. These results demonstrated that hormones generated by ovaries played important roles in regulating hepatic glucose and lipid metabolism and communicating with the gut microbiota in females.

Cigarette smoking exposure breaks the homeostasis of cholesterol and bile acid metabolism and induces gut microbiota dysbiosis in mice with different diets.

Exposure of humans to second-hand smoking (SHS) increases glucose and lipid metabolic disorders. The link of hepatic metabolic dysfunction to environmental cigarette smoking has been noticed, but the related mechanism is still unclear. C57BL/6 mice with normal food diet (NFD) or high fat diet (HFD) were exposed to 15 min cigarette smoking twice a day in a 0.038 m3 box for 4 weeks, and the concentration of nicotine in the air of the box was 21.05 mg/m3 during the smoke exposure. Liver tissues and serum were collected for gene expression and biochemistry test. The fecal microbiota was also checked through 16S rDNA sequences. Cigarette smoking exposure increased the accumulation of total cholesterol (TC) in liver, and the expression of cholesterol synthesis-related genes was upregulated. The expression of CYP8B1 protein was significantly down-regulated, and the ratio of cholic acid (CA) to chenodeoxycholic acid (CDCA) was significantly reduced in the liver of mice exposed to cigarette smoking especially for HFD group. Cigarette smoking exposure caused insulin resistance in the liver of mice with HFD. The composition of the gut microbiota was altered with the exposure of cigarette smoking, and the change of the distribution of primary bile acids might be one of the reasons. It was concluded that cigarette smoking would break the homeostasis of cholesterol and bile acids metabolism and changed the composition of gut microbiota. Our discoveries confirmed that smoking bans are important for the public health.

Potential risk of impertinent administration of methylprednisolone in lumbar spine surgery: A case report.

INTRODUCTION: Several complications of intravenous administration of Methylprednisolone in spine surgery have been reported previously. However, perioperative Addisonian crisis resulting from postoperative routine cessation of intravenous Methylprednisolone has been rarely reported. We here report a case of perioperative Addisonian crisis induced by postoperative routine cessation of intravenous Methylprednisolone. PRESENTATION OF CASE: To report a 56-year-old lady was diagnosed with Addisonian crisis on postoperative duration of lumbar spine surgery after routine cessation of intravenous Methylprednisolone on postoperative day 5. DISCUSSION: There are potential risk and medical complexity of the intravenous administration of Methylprednisolone perioperatively when patients underwent spine surgery, especially the patients with a history of adrenal insufficiency or hypothyroidism, and other endocrine diseases. The early diagnosis and effective replacement therapy after cessation of intravenous glucocorticoid to keep normal serum hormone levels can reduce risk and complication of Addisonian crisis. CONCLUSION: Addisonian crisis may be triggered by the discontinuation of exogenous glucocorticoid. Physicians need to be immediately aware of this potentially lethal complication in patients with endocrine system diseases.

Dihydroartemisinin ameliorates dextran sulfate sodium induced inflammatory bowel diseases in mice.

In the present study, the effects of dihydroartemisinin (DHA) on inflammatory bowel diseases (IBD) mice model induced by dextran sulfate sodium (DSS) were determined. Hematoxylin and eosin staining was used to assess the intestines of mice treated with DSS and DHA. The expression of inflammatory factors and cell junction-associated genes was measured using reverse transcription-quantitative PCR (RT-qPCR) and Western blot. The effects of DSS and DHA on the gut microbiome were measured using 16S recombinant (r) DNA gene analysis. DHA could improve the diarrhea and bloody stool induced by DSS, and decrease the serum levels of TNF-α, IL-1ß and IL-23 of the DSS group. DHA could notably reduce the infiltration of the inflammatory cells and significantly decrease the expression of TNF-α and IL-1ß in the intestines of the DSS treated mice. The expression of cell junction-associated genes such as EpCAM and Claudins, were down-regulated in the DSS group, and DHA could recover the expression of these cell junction-associated genes. The 16S rDNA gene analysis demonstrated that Bacteroidetes and Verrucomicrobia decreased, while Firmicutes and Proteobacteria increased in the DSS group, and DHA could recover the abundance of these gut bacteria altered by DSS. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed that DHA could partly recover the pathways altered by DSS. DHA could obviously ameliorate the symptoms of IBD induced by DSS by regulation of the expression of inflammation and cell junction-associated genes and gut microbiota, suggesting its potential for the treatment of IBD.

Application of land use regression to assess exposure and identify potential sources in PM2.5, BC, NO2 concentrations.

BACKGROUND: Understanding spatial variation of air pollution is critical for public health assessments. Land Use Regression (LUR) models have been used increasingly for modeling small-scale spatial variation in air pollution concentrations. However, they have limited application in China due to the lack of spatially resolved data. OBJECTIVE: Based on purpose-designed monitoring networks, this study developed LUR models to predict fine particulate matter (PM2.5), black carbon (BC) and nitrogen dioxide (NO2) exposure and to identify their potential outdoor-origin sources within an urban/rural region, using Taizhou, China as a case study. METHOD: Two one-week integrated samples were collected at 30 PM2.5 (BC) sites and 45 NO2 sites in each two distinct seasons. Samples of 1/3 of the sites were collected simultaneously. Annual adjusted average was calculated and regressed against pre-selected GIS-derived predictor variables in a multivariate regression model. RESULTS: LUR explained 65% of the spatial variability in PM2.5, 78% in BC and 73% in NO2. Mean (±Standard Deviation) of predicted PM2.5, BC and NO2 exposure levels were 48.3 (±6.3) µg/m3, 7.5 (±1.4) µg/m3 and 27.3 (±8.2) µg/m3, respectively. Weak spatial corrections (Pearson r = 0.05-0.25) among three pollutants were observed, indicating the presence of different sources. Regression results showed that PM2.5, BC and NO2 levels were positively associated with traffic variables. The former two also increased with farm land use; and higher NO2 levels were associated with larger industrial land use. The three pollutants were correlated with sources at a scale of ≤5 km and even smaller scales (100-700m) were found for BC and NO2. CONCLUSION: We concluded that based on a purpose-designed monitoring network, LUR model can be applied to predict PM2.5, NO2 and BC concentrations in urban/rural settings of China. Our findings highlighted important contributors to within-city heterogeneity in outdoor-generated exposure, and indicated traffic, industry and agriculture may significantly contribute to PM2.5, NO2 and BC concentrations.

Efficacy and complications of 125I seeds combined with percutaneous vertebroplasty for metastatic spinal tumors: A literature review.

To review the efficacy and complications of 125I seeds combined with percutaneous vertebroplasty for the treatment of metastatic spinal tumors. We searched PubMed/MEDLINE from its inception to November 2018 for articles on metastatic spinal tumors treated with 125I seeds combined with percutaneous vertebroplasty. A total of 273 articles were identified in PubMed/MEDLINE based on the search criteria. After deleting duplicate articles including two retrospective studies and three case control studies, five studies were included in this systematic review. In total, 161 patients aged from 49.2 to 62 years were included. The operative levels consisted of the thoracic vertebrae and lumbar vertebrae. Bone cement leakage occurred in 7 cases. None of the patients developed radiation myelopathy. Percutaneous vertebroplasty plus 125I seeds implantation is an effective palliative treatment and can alleviate back pain and enhance vertebral body strength in patients with end-stage spinal metastatic tumors. In future research, the effective dosage of 125I seeds implantation, the anchoring of seeds with safe distance, and the bone cement distribution in the vertebral body will be next research hotspot.

Fatty liver and alteration of the gut microbiome induced by diallyl disulfide.

Diallyl disulfide (DADS) is one of the primary components of garlic and it exhibits a broad range of biological activities. In the present study, the effects of DADS on lipid metabolism and its potential role in the modulation of the gut microbiome were determined. Hematoxylin and eosin and oil­red O staining were used to assess the liver and intestinal tissues of mice treated with DADS. The expression of lipid metabolism­associated genes was measured using reverse transcription­quantitative PCR (RT­qPCR). The effects of DADS on the gut microbiome were measured using 16S recombinant (r)DNA gene analysis. The results revealed that the serum non­esterified free fatty acids, high density lipoprotein­cholesterol, low density lipoprotein­cholesterol, serum total cholesterol, liver triglyceride and total cholesterol levels of the mice fed with a low­dose of DADS was significantly higher when compared with the control. Hematoxylin and eosin and oil­red O staining demonstrated that DADS induced fatty liver in mice. The results of the RT­qPCR revealed that the expression levels of a number of lipid metabolism­associated genes were altered in the livers of mice treated with DADS. The 16S rDNA gene analysis demonstrated that the mice fed on a normal diet treated with a low­dose of DADS had decreased levels of bacteria from the Bacteroidetes phyla and increased levels of bacteria from the Firmicutes phyla. The Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed the top 20 pathways enriched in the low­dose DADS group of mice fed with a normal diet. In the present study, low­dose DADS induced fatty liver and altered the gut microbiota, similar to the phenotype induced by a high fat diet, by regulating the expression of lipid metabolism associated genes.

Potential Complications of Percutaneous Vertebroplasty Combined with Interstitial Implantation of 125I Seeds for Metastatic Spinal Tumors: A Case Report and Literary Review.

Percutaneous vertebroplasty is often used to acquire the stability of the spine and relieve the pain caused by osteoporotic vertebral compressive fracture (OVCF). 125I seeds have been used for application of local therapy for tumors. A combined treatment was reported in previous literatures. Thus, this case report is aimed at reporting a patient with an occurrence of delayed radioactive myelopathy, who accepted percutaneous vertebroplasty combined with interstitial implantation of 125I seeds for metastatic spinal tumors, and at reviewing the published literatures.

Estimation of personal PM2.5 and BC exposure by a modeling approach - Results of a panel study in Shanghai, China.

BACKGROUND: Epidemiologic studies of PM2.5 (particulate matter with aerodynamic diameter ≤2.5 µm) and black carbon (BC) typically use ambient measurements as exposure proxies given that individual measurement is infeasible among large populations. Failure to account for variation in exposure will bias epidemiologic study results. The ability of ambient measurement as a proxy of exposure in regions with heavy pollution is untested. OBJECTIVE: We aimed to investigate effects of potential determinants and to estimate PM2.5 and BC exposure by a modeling approach. METHODS: We collected 417 24 h personal PM2.5 and 130 72 h personal BC measurements from a panel of 36 nonsmoking college students in Shanghai, China. Each participant underwent 4 rounds of three consecutive 24-h sampling sessions through December 2014 to July 2015. We applied backwards regression to construct mixed effect models incorporating all accessible variables of ambient pollution, climate and time-location information for exposure prediction. All models were evaluated by marginal R2 and root mean square error (RMSE) from a leave-one-out-cross-validation (LOOCV) and a 10-fold cross-validation (10-fold CV). RESULTS: Personal PM2.5 was 47.6% lower than ambient level, with mean (±Standard Deviation, SD) level of 39.9 (±32.1) µg/m3; whereas personal BC (6.1 (±2.8) µg/m3) was about one-fold higher than the corresponding ambient concentrations. Ambient levels were the most significant determinants of PM2.5 and BC exposure. Meteorological and season indicators were also important predictors. Our final models predicted 75% of the variance in 24 h personal PM2.5 and 72 h personal BC. LOOCV analysis showed an R2 (RMSE) of 0.73 (0.40) for PM2.5 and 0.66 (0.27) for BC. Ten-fold CV analysis showed a R2 (RMSE) of 0.73 (0.41) for PM2.5 and 0.68 (0.26) for BC. CONCLUSION: We used readily accessible data and established intuitive models that can predict PM2.5 and BC exposure. This modeling approach can be a feasible solution for PM exposure estimation in epidemiological studies.

Treatment of Sagittal Fracture of the Zygomatic Arch Root Assisted by Surgical Navigation Technology.

Sagittal fracture at the temporal root of the zygomatic arch often occurs as a part of zygomaticomaxillary fractures. The authors described the application of computer-assisted navigation in the lag screw insertion for the fixation of sagittal fracture at the temporal root of zygomatic arch. Using the presurgical planning of the computer-assisted navigation system, the trajectory of lag screw insertion was designed, and the insertion depth was calculated. In the presurgical planning, the trajectory of screw insertion was placed with an anterior inclination of 10° to 15° (mean: 12.24°), and the screw insertion depth was 9.0 to 12.0 mm (mean: 10.65 mm). In the operation, the screw insertion in the fixation of the sagittal fracture was performed under the guidance of navigation system according to the presurgical planning. The postoperative CT scan showed exact reduction and fixation of the sagittal fracture in all cases. Computer-assisted navigation is a useful tool for the lag screw insertion in the precise fixation of sagittal fracture at the temporal root of the zygomatic arch in complex zygomaticomaxillary fractures.

Possible Mediation by Methylation in Acute Inflammation Following Personal Exposure to Fine Particulate Air Pollution.

Air pollution may increase cardiovascular and respiratory risk through inflammatory pathways, but evidence for acute effects has been weak and indirect. Between December 2014 and July 2015, we enrolled 36 healthy, nonsmoking college students for a panel study in Shanghai, China, a city with highly variable levels of air pollution. We measured personal exposure to particulate matter with an aerodynamic diameter less than or equal to 2.5 µm (PM2.5) continuously for 72 hours preceding each of 4 clinical visits that included phlebotomy. We measured 4 inflammation proteins and DNA methylation at nearby regulatory cytosine-phosphate-guanine (CpG) loci. We applied linear mixed-effect models to examine associations over various lag times. When results suggested mediation, we evaluated methylation as mediator. Increased PM2.5 concentration was positively associated with all 4 inflammation proteins and negatively associated with DNA methylation at regulatory loci for tumor necrosis factor alpha (TNF-α) and soluble intercellular adhesion molecule-1. A 10-µg/m3 increase in average PM2.5 during the 24 hours preceding blood draw corresponded to a 4.4% increase in TNF-α and a statistically significant decrease in methylation at one of the two studied candidate CpG loci for TNF-α. Epigenetics may play an important role in mediating effects of PM2.5 on inflammatory pathways.

Estimation of residential fine particulate matter infiltration in Shanghai, China.

Ambient concentrations of fine particulate matter (PM2.5) concentration is often used as an exposure surrogate to estimate PM2.5 health effects in epidemiological studies. Ignoring the potential variations in the amount of outdoor PM2.5 infiltrating into indoor environments will cause exposure misclassification, especially when people spend most of their time indoors. As it is not feasible to measure the PM2.5 infiltration factor (Finf) for each individual residence, we aimed to build models for residential PM2.5Finf prediction and to evaluate seasonal Finf variations among residences. We repeated collected paired indoor and outdoor PM2.5 filter samples for 7 continuous days in each of the three seasons (hot, cold and transitional seasons) from 48 typical homes of Shanghai, China. PM2.5-bound sulfur on the filters was measured by X-ray fluorescence for PM2.5Finf calculation. We then used stepwise-multiple linear regression to construct season-specific models with climatic variables and questionnaire-based predictors. All models were evaluated by the coefficient of determination (R2) and root mean square error (RMSE) from a leave-one-out-cross-validation (LOOCV). The 7-day mean (±SD) of PM2.5Finf across all observations was 0.83 (±0.18). Finf was found higher and more varied in transitional season (12-25 °C) than hot (>25 °C) and cold (<12 °C) seasons. Air conditioning use and meteorological factors were the most important predictors during hot and cold seasons; Floor of residence and building age were the best transitional season predictors. The models predicted 60.0%-68.4% of the variance in 7-day averages of Finf, The LOOCV analysis showed an R2 of 0.52 and an RMSE of 0.11. Our finding of large variation in residential PM2.5Finf between seasons and across residences within season indicated the important source of outdoor-generated PM2.5 exposure heterogeneity in epidemiologic studies. Our models based on readily available data may potentially improve the accuracy of estimates of the health effects of PM2.5 exposure.