in recent years , the incidence of chronic obstructive pulmonary disease ( copd ) has been 
 increasing , and according to the world health organization , copd will become the third 
 common cause of death by 20301 . an 
 epidemiological survey in japan , in 2004 , found that the prevalence of copd among japanese 
 adults , aged 40  years or older , was 8.6% , corresponding to approximately 5,300,000 
 persons2 . the prevention of copd onset 
 is an urgent public health issue in japan as the incidence is expected to rise further . body composition undergoes significant changes with aging and , specifically , there is a 
 decrease in muscle mass while fat mass , particularly visceral fat mass , increases3,4,5 . the accumulation of visceral fat is 
 associated with insulin resistance and impaired glucose tolerance , elevated blood pressure , 
 and disorder of lipid metabolism , such as metabolic syndrome ( mets)6 and is considered a risk factor of arteriosclerotic7 . furthermore , a recent study reported that 
 abdominal obesity is associated with a decreased respiratory function and the onset of 
 copd8,9,10 . visceral fat is associated with greater 
 systemic inflammation and insulin resistance than subcutaneous fat11 , 12 , however no 
 studies have examined the independent association of visceral fat with the respiratory 
 function by distinguishing between visceral fat and subcutaneous fat13 . furthermore , reduced physical activity , which causes visceral fat accumulation , is 
 associated with copd , because shortness of breath , a cardinal symptom for copd , results in 
 diminished physical activity . it has been suggested that physical activity affects 
 prognosis , in terms of increased mortality , in copd14 , 15 , and that it also affects 
 the risk of onset of copd16 . therefore , 
 it is crucial to determine the association between lifestyle , such as the physical activity , 
 and respiratory function in the workers in order to prevent the future onset of copd . sarcopenia , the age - related loss of muscle mass and muscle strength17 , is an important risk factor for frailty , leading to falls 
 and bedridden status18,19,20 . respiratory 
 function also decreases with age21 , 22 and it is postulated that this is related 
 to respiratory function and muscle mass . however , although studies for patients with copd 
 have shown that systemic inflammation and skeletal muscle disorders are associated with 
 reduced physical activity23 , 24 , there are limited reported studies on the association 
 between respiratory function and muscle mass in the working age population in the abscence 
 of copd25 . this study analyzes the association among respiratory function , parameters of body 
 composition , such as muscle mass and the visceral fat area ( vfa ) , and lifestyle parameters 
 that are assumed to be associated with body composition . the aim of this study was to 
 identify factors related to physical characteristics and lifestyle that affect the pulmonary 
 function . respiratory function measurement was carried out for 127 men employed in 2 companies 
 followed by the health measurement conducted by the research center for the health promotion 
 and employment support , kyushu rousai hospital in 2015 . following the provision of 
 information on the purpose of the study and on privacy protection of participants , consent exclusion criteria were subjects with blanks to 
 self - administered questionnaires , pulmonary disease or a history of pulmonary disease , and 
 forced expiratory volume in one second percent ( fev1/fvc)<0.7 . a total of 97 healthy 
 male workers were therefore recruited for this study . the average age was 45.5  9.2 
 ( years ) , weight was 73.5  11.3 ( kg ) , and height was 171.5  5.4 ( cm ) . the breakdown , 
 according to the type of industry , and based on the international standard classification of 
 occupations ( major groups)26 was as 
 follows : managers ( 33 ) ; professionals , technicians and associate professionals ( 22 ) ; 
 clerical support workers ( 30 ) ; service and sales workers ( 9 ) ; craft and related trades 
 workers ( 1 ) ; and others ( 9 ) . the study complied with guidelines set out by the ethics 
 committee of the kyushu nutrition welfare university , higashi chikushi junior college . self - administered questionnaire was used to collect the following information : age , height , 
 disease under treatment , and prevalence of mets risk factors ( hypertension , dyslipidemia , 
 diabetes , obesity ) . information on smoking habits and physical activity , as a part of 
 lifestyle information , was also collected via self - administered questionnaires . the subject 
 smoking habit was described by the smoking index ( pack - years ) , calculated by multiplying the 
 number of years the person has smoked by the mean number of cigarettes smoked per day . physical ativity was evaluated using the short version of the international physical 
 activity questionnaire ( ipaq ) , japanese edition . the reliability and validity of this 
 questionnaire has previously been established27 , 
 28 . physical activity was calculated 
 physical activity ( mets.mins ) by multiplying the intensity of the physical activity by the 
 time , according to high strength , moderate strength , and locomotor intensity of the exercise 
 in ipaq . weight , body mass index , waist circumference , percentage of body 
 fat , fat free mass , and waist to hip ratio were measured by body composition analyzer 
 ( inbody 720 , inbody co. , ltd . , upper extremity muscle 
 mass , lower extremity muscle mass , upper extremity fat mass , and lower extremity fat mass 
 were calculated from relevant measurements of muscle and fat mass ( left upper extremity , 
 right upper extremity , left lower extremity , right lower extremity ) . the skeletal muscle 
 index ( smi)29 , one of the diagnostic 
 indexes for sarcopenia , using a visceral fat measuring device ( hds-2000 dualscan , omron healthcare 
 co. , ltd . , kyoto , japan ) , the vfa and the subcutaneous fat area ( sfa ) were measured . spirometry test was performed according to guidelines developed by the committee of 
 pulmonary physiology of the japanese respiratory society30 . expiratory volume in one second ( fev1 ) , forced vital capacity ( fvc ) , forced expiratory 
 volume in one second percent ( fev1/fvc ) were measured by an electronic spirometer ( autospiro 
 as-507 , minato medical science co. , ltd . , osaka , japan ) . predicted fev1 and predicted fvc 
 were calculated using the equation developed by the japanese respiratory society31 . the values were described as mean  standard deviation or median ( interquartile range 
 2575% ) , for normally and not normally distributed data , respectively . analyses were performed using ibm spss statistics 
 22.0 ( ibm japan , ltd . , correlations between respiratory function and body composition , basic information , and 
 lifestyle were analyzed using pearson s correlation coefficient for continuous variables or 
 spearman correlation coefficient for ordinal variables . two groups , identified according to 
 prevalence of mets risk factors , were compared using two - sample t - test or mann - whitney test , 
 according to the distribution . a multiple stepwise linear regression analysis was performed with the pulmonary function as 
 the dependent variable . variables with a significant association with pulmonary function on 
 univariate analysis were imputed as independent . it was confirmed that the variance inflation factor ( vif ) of independent 
 variables was less than 10 to avoid the potential issue of multicollinearity . table 1table 1.the characteristics of analysis subjectsvariablesvaluesbasic informationage ( years)46.0 ( 39.053.0)height ( cm)171.5  5.4no mets risk factors82 ( 84.5)lifestyle informationsmoking index ( pack - years)120.0 ( 0.0400.0)high strength time ( min)0.0 ( 0.0480.0)moderate strength time ( min)0.0 ( 0.0420.0)locomotor intensity time ( min)396.0 ( 115.5693.0)physical activity ( mets.mins)960.0 ( 495.01485.0)body compositionweight ( kg)71.9 ( 66.681.3)body mass index ( kg / m)24.8 ( 22.627.4)waist circumference ( cm)83.8 ( 77.892.2)percentage of body fat ( % ) 22.6 ( 18.428.8)fat free mass ( kg)55.7  5.3waist to hip ratio0.9 ( 0.80.9)upper extremity muscle mass ( kg)6.0  0.8lower extremity muscle mass ( kg)18.1  1.9trunk muscle mass ( kg)24.4  2.5upper extremity fat mass ( kg)1.8 ( 1.32.7)lower extremity fat mass ( kg)5.1 ( 4.06.7)smi ( kg / m)8.2  0.6visceral fat area ( cm)81.8 ( 62.5106.4)subcutaneous fat area ( cm)169.0 ( 127.1218.3)pulmonary functionfev1 ( l)3.6  0.5fev1 % predicted96.6  10.4fvc ( l)4.4  0.6fvc % predicted101.3  10.9fev1/fvc ( % ) 82.1  4.8the values were described as mean  standard deviation or median ( interquartile range 
 2575% ) , for normally and not normally distributed data , respectively . mets : metabolic syndrome , smi : 
 skeletal muscle index , fev1 : forced expiratory volume in one second , fvc : forced vital 
 capacity shows the characteristics , pulmonary function , body composition , and lifestyle 
 of the subjects included in the study . the values were described as mean  standard deviation or median ( interquartile range 
 2575% ) , for normally and not normally distributed data , respectively . mets : metabolic syndrome , smi : 
 skeletal muscle index , fev1 : forced expiratory volume in one second , fvc : forced vital 
 capacity the correlation between pulmonary function and lifestyle are shown in table 2table 2.the correlation between pulmonary function and lifestylefev1 ( l)fvc ( l)smoking index ( pack - years)0.208 * 0.200 * high strength time ( min)0.1830.197moderate strength time ( min)0.0240.003locomotor intensity time ( min)0.0900.120physical activity ( mets.mins)0.0310.007 * p<0.05 . all were analyzed using spearman correlation coefficient .. both fev1 and fvc were negatively associated with the smoking index 
 ( p<0.05 ) . table 3table 3.the difference in pulmonary function according to prevalence of mets risk 
 factorsprevalence of mets riskfev1 ( l)fvc ( l)valuesvaluesno3.6  0.5 * 4.4  0.5 * yes3.3  0.44.0  0.6*p<0.05 ( vs. yes ) . mets : metabolic 
 syndrome shows the difference in pulmonary function according to prevalence of mets 
 risk factors of the individuals . a significant difference was observed with respect to 
 presence or absence of mets risk factors according to the fev1 and fvc , the absence of mets 
 risk factors ( p<0.05 ) was significantly associated with higher fev1 and fvc . * mets : metabolic 
 syndrome table 4table 4.the correlation coefficient between pulmonary function and body 
 compositionfev1 ( l)fvc ( l)age ( year)0.578 * * 0.511 * * height ( cm)0.501 * * 0.552 * * weight ( kg ) 0.1490.149body mass index ( kg / m ) 0.0640.087waist circumference ( cm ) 0.0040.002percentage of body fat ( % ) 0.227 * 0.240 * fat free mass ( kg ) 0.407 * * 0.390 * * waist to hip ratio 0.0580.051upper extremity muscle mass ( kg ) 0.306 * * 0.268 * * lower extremity muscle mass ( kg ) 0.411 * * 0.418 * * trunk muscle mass ( kg ) 0.342 * * 0.310 * * upper extremity fat mass ( kg ) 0.1640.165lower extremity fat mass ( kg ) 0.1340.143smi ( kg / m ) 0.1560.100visceral fat area ( cm ) 0.252 * 0.275 * * subcutaneous fat area ( cm ) 0.0630.083*p<0.05 , * * p<0.01 . spearman correlation coefficient.smi : skeletal muscle index shows the correlation coefficient and p - values between pulmonary function and 
 body composition . significant positive correlations were observed between fev1 and height 
 ( p<0.001 ) , fat free mass ( p<0.001 ) , upper extremity muscle mass ( p<0.005 ) , lower 
 extremity muscle mass ( p<0.001 ) , and trunk muscle mass ( p<0.001 ) , respectively . age 
 ( p<0.001 ) , percentage of body fat ( p<0.05 ) , vfa ( p<0.05 ) were negatively correlated 
 with fev1 . height ( p<0.001 ) , fat free mass ( p<0.001 ) , upper extremity muscle mass 
 ( p<0.01 ) , lower extremity muscle mass ( p<0.001 ) , and trunk muscle mass ( p<0.005 ) 
 correlated positively with fvc . age ( p<0.001 ) , percentage of body fat ( p<0.05 ) , and 
 vfa ( p<0.01 ) correlated negatively with fvc . * p<0.05 , * * p<0.01 . spearman correlation coefficient.smi : skeletal muscle index the results of the multiple stepwise linear regression analysis that assumed fev1 and fvc 
 as dependent variables , adjusted by age and height , are shown in tables 5table 5.the multiple stepwise linear 
 regression analysis that assumed fev1 as a dependent variable with being adjusted by 
 age and heightpartial regression coefficientstandard partial regression coefficient95% confidence intervalvif ( constant)0.4532.453 to 3.359age0.0230.413**0.032 to 0.0141.252height0.0190.1950.001 to 0.0392.101percentage of body fat0.0333.847fat free mass0.0230.239 * 0.000 to 0.0462.693upper extremity muscle mass0.02211.305lower extremity muscle mass0.16312.546trunk muscle mass0.03313.846visceral fat area0.0040.290**0.007 to 0.0021.542smoking index0.0301.214no mets risk factors0.0411.127*p<0.05 , * * p<0.01 . vif : variance inflation factor , mets : metabolic syndrome and 6table 6.the multiple stepwise linear regression analysis that assumed fvc as a dependent 
 variable with being adjusted by age and heightpartial regression coefficientstandard partial regression coefficientp value95% confidence intervalvif ( constant)2.5110.1305.774 to 0.751age0.0240.3610.000**0.034 to 0.0141.117height0.0480.4220.000**0.030 to 0.0661.109percentage of body fat0.0920.5323.815fat free mass0.1850.1312.693upper extremity muscle mass0.1290.2322.081lower extremity muscle mass0.1100.4714.119trunk muscle mass0.1560.1862.467visceral fat area0.0040.2160.005**0.006 to 0.0011.017smoking index0.0250.7641.196no mets risk factors0.1010.2021.116*p<0.05 , * * p<0.01 . vif : variance inflation factor , mets : metabolic syndrome . from the results of fev1 as dependent variable , vfa and fat free mass were 
 identified . the multiple regression model was significant , and the adjusted r 
 was 0.497 . from the results of fvc as dependent variable , vif : variance inflation factor , mets : metabolic syndrome * p<0.05 , * * p<0.01 . among diseases that are associated with aging , copd is the main cause of morbidity and 
 mortality in the elderly people32 . specifically , the decrease in fev1 has been shown as an independent factor associated with 
 increased mortality33 . thus , prevention 
 of pulmonary function decline in younger population is important because the age - related 
 decrease in pulmonary function results in the onset of copd and in an increased risk of 
 death in elderly people . the purpose of this study was to examine the workers and identify 
 factors related to physical characteristics and lifestyle that affect the pulmonary 
 function . this study found that vfa and percentage of body fat are associated with a decreased 
 pulmonary function in multiple regression analysis , adjusted by age and height . previous 
 studies on the association between pulmonary function and physical characteristics have 
 shown that an index of central obesity , including waist circumference and waist to hip 
 ratio , and abdominal height expressing visceral fat accumulation34 were associated with a decreased respiratory function9 , 10 , 35 . diaphragmatic movement is limited in 
 obesity while abdominal pressure is increased , particularly with the accumulation of 
 visceral fat36 . therefore , it is 
 postulated that a reduction in expiratory reserve volume , fev1 , and fvc is due to a 
 mechanical limitation of air flow , regardless of respiratory tract inflammation37 , 38 . visceral fat has the function of an endocrine organ and secretes 
 interleukin-6 , tnf- , and leptin . systemic inflammation is shown to be associated with pulmonary 
 function41 , 42 , and this study shows that systemic inflammation combined with the 
 presence of visceral fat may have an influence on decreased pulmonary function . conversely , lifestyle factors affecting pulmonary function in the working generation were 
 not identified . the smoking habit also was not identified as a variable associated with the 
 pulmonary function by the multiple regression analysis although the correlation was observed 
 between smoking habit and pulmonary function . according to the guidelines of the japanese 
 respiratory society43 , copd is defined as 
  an inflammatory disease of the lungs that is caused by long - term inhalation exposure to 
 noxious substances such as tobacco smoke  . the most important factor causing copd is 
 cigarette smoke ( smoking and passive smoking ) . specifically , smoking promotes the 
 exacerbation of pulmonary function decline with aging , and the decrease in pulmonary 
 function is greater compared to that in nonsmokers44 . therefore , future lifestyle changes are important because 
 respiratory function decreases and the risk of copd onset increases with time even if the 
 smokers of the working population have good respiratory function at present . it can not be examined that the effects of 
 passive smoking because the history of passive smoking is not assessed in this study . previous studies have shown that passive smoking is independently associated with copd 
 onset45 from other factors , and that 
 parental smoking habits influence the development of the respiratory function in 
 children46 . therefore , it is necessary 
 to investigate further the association between cigarette smoke , including a history of 
 passive smoking , and respiratory function . studies in elderly people have shown that fat free mass , muscle in the trunk and low 
 extremity are associated with respiratory function9 , 
 10 , 25 . in addition , it has been reported that sarcopenia , an age - related 
 reduction in muscle mass47 , causes 
 breathing muscle weakness . furthermore , it has been reported that skeletal muscle disorders 
 associated with systemic inflammation and a reduction in physical activity may occur in 
 patients with copd23 . however , upper 
 extremity muscle mass , lower extremity muscle mass , trunk muscle mass , and smi were not 
 identified as the key factors affecting pulmonary function in multiple regression analysis . smi calculated by using upper extremity muscle mass and lower extremity muscle mass except 
 the trunk muscle mass was unrelated to a pulmonary function even by univariate analysis . it 
 has been suggested that in a working population , smi can not be an index for respiratory 
 function because smi , as an index of sarcopenia , is unrelated to pulmonary function . conversely , it is postulated that muscle mass decline with aging affects respiratory 
 function because of the association between muscle mass and respiratory function is in 
 elderly people and the patients with copd . there may be the need to promote maintenance and 
 improvement of muscle mass in the working population in order to reduce the risk of future 
 respiratory function deterioration and copd onset . it will be necessary to examine the 
 effects of a reduction in age - related muscle mass on pulmonary function . this study examined factors to affecting pulmonary function in the working population in 
 order to prevent decreased pulmonary function . it was found that fev1 was associated with 
 vfa and fat free mass , and that fvc was associated with vfa independently of age and height . these results may be valuable in preventing the decrease in respiratory function and , hence , 
 in further preventing the onset of copd . guidance on the prevention of visceral fat 
 accumulation is important , and in future , it will be necessary to examine how body 
 composition and lifestyle of the working population affect age - related change in respiratory 
 function .
[ purpose ] the purpose of this study was to identify factors related to physical 
 characteristics and lifestyle that affect pulmonary function . 
 [ subjects and methods ] 
 ninety seven healthy male workers were recruited for this study , and basic information and 
 details about lifestyle were collected . 
 body composition analyzer and visceral fat 
 measuring device were conducted as measurements . 
 pulmonary function was measured using 
 spirometer . 
 a multiple stepwise linear regression analysis was performed with pulmonary 
 function as the dependent variable . 
 variables with a significant association with 
 pulmonary function on univariate analysis were imputed as independent variables . 
 [ results ] 
 height , fat free mass , upper extremity muscle mass , lower extremity muscle mass , and trunk 
 muscle mass had significant positive correlations with fev1 and fvc . 
 age , percentage of 
 body fat , and visceral fat area were negatively correlated with fev1 and fvc . 
 regarding 
 the association between pulmonary function and lifestyle , a significant difference was 
 found between the smoking index and the presence or absence of metabolic syndrome risk 
 factors and both fev1 and fvc . 
 the multiple stepwise linear regression analysis with fev1 
 as the dependent variable , adjusted for age and height , revealed that visceral fat area 
 and fat free mass were significantly associated with fev1 . a similar analysis , fvc as the 
 dependent variable identified visceral fat area . 
 [ conclusion ] fev1 was independently 
 associated with visceral fat area and fat free mass . 
 fvc was independently associated with 
 visceral fat area . 
 these results may be valuable in preventing the decrease in respiratory 
 function and , hence , in further preventing the onset of copd .