Yoshihiro Kitahara

Kochi University, Kōchi-shi, Kochi-ken, Japan

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Publications (7)21.08 Total impact

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    ABSTRACT: A growing body of evidence suggests that there is a relationship between impaired lung function and the risk of developing diabetes mellitus (DM). However, it is not known if this reflects a causal effect of lung function on glucose metabolism. To clarify the relationship between lung function and the development of DM, we examined the incidence of newly diagnosed prediabetes (a precursor of DM) among subjects with normal glucose tolerance (NGT) at baseline. Primary analysis of an occupational cohort with both cross-sectional and longitudinal data (follow-up duration mean±SD: 28.4±6.1 months). Data were analysed from 1058 men in a cross-sectional study and from 560 men with NGT in a longitudinal study. OUTCOMES AND METHODS: Impaired lung function (per cent predicted value of forced vital capacity (%FVC) or per cent value of forced expiratory volume 1 s/FVC (FEV(1)/FVC ratio)) in relation to the ratio of prediabetes or DM in a cross-sectional study and development of new prediabetes in a longitudinal study. NGT, prediabetes including impaired glucose tolerance (IGT) and increased fasting glucose (IFG) and DM were diagnosed according to 75 g oral glucose tolerance tests. %FVC at baseline, but not FEV(1)/FVC ratio at baseline, was significantly associated with the incidences of DM and prediabetes. Among prediabetes, IGT but not IFG was associated with %FVC. During follow-up, 102 subjects developed prediabetes among those with NGT. A low %FVC, but not FEV(1)/FVC ratio, was predictive of an increased risk for development of IGT, but not of IFG. Low lung volume is associated with an increased risk for the development of prediabetes, especially IGT, in Japanese men. Although there is published evidence for an association between chronic obstructive pulmonary disease and DM, prediabetes is not associated with the early stage of COPD.
    BMJ Open 01/2013; 3(2). · 1.58 Impact Factor
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    ABSTRACT: To investigate the influence of cigarette smoking on exercise capacity, respiratory responses and dynamic changes in lung volume during exercise in patients with type 2 diabetes. Forty-one men with type, 2 diabetes without cardiopulmonary disease were recruited and divided into 28 non-current smokers and 13 current smokers. All subjects received lung function tests and cardiopulmonary exercise testing using tracings of the flow-volume loop. Exercise capacity was compared using the percentage of predicted oxygen uptake at maximal workload (%VO2max). Respiratory variables and inspiratory capacity (IC) were compared between the two groups at rest and at 20%, 40%, 60%, 80% and 100% of maximum workload. Although there was no significant difference in lung function tests between the two groups, venous carboxyhemoglobin (CO-Hb) levels were significantly higher in current smokers. %VO2max was inversely correlated with CO-Hb levels. Changing patterns in respiratory rate, respiratory equivalent and IC were significantly different between the two groups. Current smokers had rapid breathing, a greater respiratory equivalent and a limited increase in IC during exercise. Cigarette smoking diminishes the increase in dynamic IC in patients with type 2 diabetes. As this effect of smoking on dynamic changes in lung volume will exacerbate dynamic hyperinflation in cases complicated by chronic obstructive pulmonary disease, physicians should consider smoking habits and lung function when evaluating exercise capacity in patients with type 2 diabetes.
    Hiroshima journal of medical sciences 06/2012; 61(2):29-36.
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    ABSTRACT: Patients with type 2 diabetes have impaired exercise capacity. While numerous factors are known to contribute to impaired exercise capacity, the role of lung function remains unclear. We conducted the present study to investigate the influence of lung function on exercise capacity in patients with type 2 diabetes. Cardiopulmonary exercise testing was carried out in 31 male patients with type 2 diabetes without diabetic complications or cardiopulmonary diseases. Patients with abnormal spirometry results such as a percentage of predicted forced vital capacity (%FVC) < 80% and/or a ratio of forced expiratory volume in one second (FEV1) to FVC (FEV1/FVC) < 70% were excluded from the study. We used the percentage of predicted maximal oxygen uptake (%VO2max) as an index of exercise capacity. The correlations between %VO2max and lung function and other factors known to be associated with impaired exercise capacity were then assessed. Univariate analysis revealed %VO2max correlated significantly with percentage of predicted FEV1 (%FEV1), duration of type 2 diabetes, regular exercise habits, and systolic and diastolic blood pressures. In a multivariate analysis, %FEV1 and regular exercise habits were found to be independent determinants of %VO2max. A mild reduction in %FEV1, which may be a complication of diabetes, is associated with impaired exercise capacity in patients with type 2 diabetes. When evaluating spirometric values in patients with type 2 diabetes, a reduction in %FEV1 should be noted even when both %FVC and FEV1/FVC are within normal limits.
    Hiroshima journal of medical sciences 03/2010; 59(1):7-13.
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    ABSTRACT: The presence of productive cough was an independent risk factor for the development of COPD in Japanese men, particularly former smokers. Stage 0 disease, as defined in GOLD 2001 guidelines, is relevant for the identification of subjects at risk of developing COPD. It has yet to be determined whether the presence of productive cough is a risk factor for the development of COPD. The aim of the present study was to obtain more information on this potential association in Japanese men. Seven hundred and eighty-three men with normal spirometry who did not have respiratory disease were recruited. The subjects were divided into three groups: group A, non-smokers; group B, those with a positive smoking history without productive cough; and group C, those with a positive smoking history and productive cough. The incidence rates of COPD were compared among the three groups and the relative risks for the development of COPD were assessed. During the mean follow-up period of 33.6+/-20.4 months, 19 (2.4%) subjects developed COPD. The incidence rate of COPD was significantly higher in group C than in group B (10.1 vs 2.2%, P=0.003). A multivariate analysis of data for all subjects, current smokers and former smokers revealed that productive cough was an independent risk factor for the development of COPD in all subjects and former smokers but not in current smokers. Productive cough was an independent risk factor for the development of COPD in Japanese men. In particular, former smokers who complain of this symptom should be regarded as being at high risk for the development of COPD. The data suggested that stage 0 disease, as defined in the Global Initiative for Chronic Obstructive Lung Disease 2001 guidelines, is relevant for the identification of subjects at risk of developing COPD.
    Respirology 02/2010; 15(2):313-8. · 2.78 Impact Factor
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    ABSTRACT: Chronic obstructive pulmonary disease (COPD) is associated with increased morbidity and mortality from cardiovascular disease. Although a close association between COPD and atherosclerosis has been speculated, such scientific information is limited. To evaluate subclinical atherosclerosis in smokers with airflow limitation. The subjects of this study were healthy middle-aged men. Smokers with airflow limitation (n = 61) and age-matched control smokers (n = 122) and control never-smokers (n = 122) without airflow limitation were included in the present study. Subjects with diabetes, acute infection, and respiratory disease other than COPD were excluded beforehand. All subjects underwent chest radiogram, spirometry, blood sampling, and carotid ultrasonography. We determined carotid intima-media thickness and focal atheromatous plaque as indicators of subclinical atherosclerosis. Mean carotid intima-media thickness was greater in smokers with airflow limitation than in control smokers (P < 0.01) and control never-smokers (P < 0.005). Focal carotid plaque was significantly more prevalent in smokers with airflow limitation than in control never-smokers (P < 0.005). Multivariate analyses showed significant associations between thickened intima-media thickness and decreased percent predicted FEV(1) (P = 0.001) and between plaque and log(10) C-reactive protein (P = 0.013) independent of age, pack-years of smoking, body mass index, peripheral mean arterial pressure, heart rate, glucose, and low-density lipoprotein cholesterol. Smokers with airflow limitation had exaggerated subclinical atherosclerosis. This study suggests that middle-aged men who are susceptible to COPD may also be susceptible to vascular atherosclerosis by smoking, and atherosclerotic change starts early in the disease process of COPD.
    American Journal of Respiratory and Critical Care Medicine 10/2008; 179(1):35-40. · 11.04 Impact Factor
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    ABSTRACT: The purpose of this study was to determine whether moderate-intensity exercise training reduces oxidative stress in patients with type 2 diabetes mellitus over 12 months. The patients were divided into 3 groups: aerobic training combined with the use of a fitness center (group A, n = 43), aerobic training only (group B, n = 44), or controls (group C, n = 16). The subjects in groups A and B were instructed to exercise at 50% of peak oxygen uptake for more than 30 minutes on at least 3 days per week over a 12 month period. In addition, the subjects in group A were instructed to use a fitness center and were taught how to perform aerobic training in the indicated manner by certified fitness instructors. We measured the levels of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a parameter of oxidative stress. Serum glycated albumin levels were reduced significantly after 6 and 12 months in groups A and B and after 12 months in group C. Urinary 8-OHdG levels decreased after 12 months in groups A and B, but remained unchanged in group C. There was a significant positive linear association between percentage changes in urinary 8-OHdG and glycated albumin levels over the 12 months. In conclusion, aerobic exercise training improved glycemic control and reduced oxidative stress in patients with type 2 diabetes mellitus. Furthermore, improvement in glycemic control was associated with a reduction in oxidative stress.
    Metabolism 03/2008; 57(2):170-6. · 3.10 Impact Factor
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    ABSTRACT: Pulse wave velocity (PWV) is a good indicator of arterial stiffness and an important predictor of cardiovascular events. Recent studies have revealed that PWV increases in patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) and it also correlates with its severity. However, the therapeutic effect of continuous positive airway pressure (CPAP) on PWV remains undetermined. To clarify this point, we started CPAP treatment on 17 OSAHS patients. Brachial-ankle PWV was measured before starting CPAP, and at 2 months and 4 months after the start of CPAP. Before the CPAP treatment, mean brachial-ankle PWV of the patients was 15.6+/-0.6 m/s, and mean Epworth sleepiness scale (ESS) score was 8.6+/-1.0. Brachial-ankle PWV was found to positively correlate with heart rate, systolic and diastolic blood pressures, mean blood pressure, and arousal index. During the study period, the CPAP treatment did not have a significant effect on heart rate, blood pressures and serum total cholesterol levels. However, it significantly improved ESS score at 4 months after the start of CPAP (P=0.001), while it effectively decreased brachial-ankle PWV at 2 months and at 4 months after the start of CPAP (P=0.010 and P=0.027, respectively). The CPAP treatment was shown to decrease brachial-ankle PWV without affecting blood pressures in OSAHS patients. Although the precise mechanism for this effect is unclear, our finding suggests a close relationship between OSAHS and arterial stiffness, while also reemphasizing the clinical importance of CPAP treatment.
    Respiratory Medicine 01/2007; 100(12):2160-9. · 2.59 Impact Factor