Subjects
Subjects were 82 patients who visited the Department of Respiratory Medicine in the affiliated hospital of the Mongolian National University of Medical Sciences in March 2012 and 2013. Patients with COPD and BA aged 40–79 years and in stable state (not in exacerbation state) were classified as “Patients”, whereas hospital patients without any respiratory diseases but with a moderate disease such as mild hypertension were recruited as “Controls”. The patients and hospital controls filled out the questionnaire three times in March, May and July. Respiratory diseases were diagnosed by respiratory specialist and pulmonary function test. The pulmonary function test was performed using spirometer HI-105 (CHEST M.I., Tokyo, Japan) and the subjects were classified into four groups according to the guidelines of The Japanese Respiratory Society; normal, obstructive, restrictive, and combined ventilatory impairment (Sasaki et al. 2001). Patients were classified as COPD or BA according to the clinical findings, spirometry results, and the onset and duration of symptoms. Patients and controls with infection or severe comorbidities such as cancer or pneumonectomy were excluded. We also excluded subjects who did not fill out 3 consecutive questionnaires and those who did not take the pulmonary function test. In total, 27 patients (16 with COPD and 11 with BA) and 27 controls were included in this study.
Questionnaire
The questionnaire is a self-completed booklet containing questions on the age, sex, smoking history, occupation, respiratory symptoms: Q1, Does the weather affect your cough?; Q2, Have you ever coughed up sputum from your chest when you do not have a cold?; Q3, Do you usually cough up sputum from your chest first thing in the morning?; Q4, How frequently do you wheeze? SF-36v2 and COOP/WONCA charts. Responses to SF-36 were on three-, five- or six-point ordinal scales, from which 8 subscales (physical functioning, PF; role limitations due to physical health problems, RP; bodily pain, BP; general health perceptions, GH; vitality, VT; social functioning, SF; role limitations due to emotional problems, RE; mental health, MH) were calculated from 0 to 100 points (min = 0, max = 100) according to the scoring manual (Fukuhara et al. 2004). Responses to the COOP/WONCA charts comprising of 8 items (physical fitness, PF; feelings, FE; daily activities, DA; social activities, SA; change of health, CH; overall health, OH; pain, PA; quality of life, QL) were scored on a five-point ordinal scale ranging from 1 to 5 (1 = best, 5 = worst) (van Weel 1993).
Measurement of ambient PM2.5 level and the analyses of their components
Ambient air was sampled in the center of Ulaanbaatar city at 47°54′53.0″N 106°55′24.2″E, away from heavy traffic and any smoke-generating facility. Fine particles with a diameter of 2.5 μm or less (PM2.5) were collected on polytetrafluoroethylene (PTFE) filters using FRM-2000 (Thermo Fisher Scientific Inc., Waltham, MA, USA) at a flow-rate of 16.7 L/min. Sampling times were 9 am to 4:50 pm and 5 pm to 8:50 am of the next morning. Personal exposure level of PM2.5 was measured using mini pump MP-∑3 (SIBATA SCIENTIFIC TECHNOLOGY, Tokyo, Japan) equipped with PTFE filter at a flow-rate of 2.50 L/min. Sampling time for mini pump was 9 am to 5 pm. Sampled filters were stored in hermetically sealed plastic bags at −20 °C. Filters were weighed, followed by conditioning at 21.5 ± 1.5 °C and 35.0 ± 5.0 % relative humidity using an electric analytical scale (ME-5F, Sartorius AG, Göttingen, Germany). PM2.5 mass concentration was calculated by subtracting the filter weight of pre-sampling from post-sampling. Carbon and ionic components contained in the particles sampled on the filters were analyzed by FUJITSU QUALITY LABORATORY (Kawasaki, Japan).
Data handling and statistical analyses
All data were handled by questionnaire IDs and managed as electronic data for the analysis. Statistical analyses were performed using the statistical software packages JMP version 11 (SAS Institute, Cary, NC, USA), including Welch’s t test and one-way analysis of variance (ANOVA) followed by Tukey’s HSD test for the parametric analyses of continuous variables of two and three groups respectively, and χ2-test for analyses of categorical data. P values <0.05 were considered significant.
Ethical considerations
The present study was approved by the Clinical Ethical Review Board of Kurume University School of Medicine. Before investigation, all participants were given explanations in person as to the purpose and method of the study, as well as information regarding handling of the results. The study was carried out upon receipt of written consent.