the association between physical activity and health is well - established . in line with this , many health institutions developed physical activity guidelines for health .
for example , the world health organization ( who ; world health organization , 2010 ) suggested that adults participate in at least 150 min of moderate - intensity physical activity , 75 min of vigorous - intensity physical activity , or an equivalent volume of moderate- to vigorous - intensity physical activity per week . nevertheless , the proportion of people who participate in the recommended level of physical activity is less than ideal in most developed countries .
for example , moderate - intensity physical activity guideline adherence rate in 2013 korea national health and nutrition examination survey ( knhanes ; ministry of health and welfare , 2014 ) was only 9.0% and 4.5% in males and females , respectively .
similarly , accelerometer - measured physical activity adherence rate of us adults was 3.5% in 20032004 national health and nutrition examination survey ( troiano et al . , 2008 ) .
( 2012 ) reported that physical inactivity , the fourth leading cause of death , caused 9% of premature mortality , 6% of coronary heart disease , and 7% of type-2 diabetes in 2008 worldwide .
metabolic syndrome is a combination of at least three of the cardiovascular disease and type-2 diabetes risk factors : hypertension , impaired glucose tolerance , abdominal obesity , elevated triglyceride level , and decreased high - density lipoprotein cholesterol level . in korea ,
the number of people with metabolic syndrome increased from 24.9% to 31.3% during 1998 and 2007 ( lim et al . , 2011 ) .
epidemiologic evidences support the association between physical inactivity and the indicators of metabolic syndrome ( barlow et al . , 2006 ; durstine et al . , 2001 ; thorogood et al . ,
moreover , physical activity is a necessary component of intervention programs to prevent cardiovascular disease and type-2 diabetes for people who already have conditions of metabolic syndrome ( dishman et al . , 2013 ) .
meanwhile , wilkinson ( 2002 ) insisted that the prevalence of noncommunicable chronic diseases is associated with economic equity of the society .
korean economic equity has decreased since late 1990 s national monetary crisis ( kim and han , 2007 ) .
accordingly , inequity in metabolic syndrome prevalence among korean women had increased in 2005 compared to 1998 ( kim and kim , 2007 ) .
moreover , research shows that socioeconomically disadvantaged groups in korea are more vulnerable to chronic diseases compared to better socioeconomic group .
for example , kim and kim ( 2007 ) reported that the incident rate of metabolic syndrome was 38%85% higher in less educated women compared to their counterparts with higher education . among many behavioral risk factors ,
research on physical activity disparities showed that people in lower socioeconomic class are generally less likely to participate in health - enhancing physical activity .
this means that different socioeconomic groups take advantage of different levels of physical activity resources such as knowledge , motivation , and social and physical environment .
moreover , physical inactivity increases chances for not only onset of chronic diseases , but also recurrence and/or further development of such conditions ( kang , 2015 ) .
therefore , it can be a double - difficulty for lower socioeconomic class with hypokinetic chronic diseases such as metabolic syndrome , because they may be less likely to participate in physical activity as a treatment purpose .
therefore , this study was purposed to investigate physical activity adherence disparities by socioeconomic status that may exist among metabolic syndrome patients in korea .
knhanes is a continuous annual surveillance system that consists of demographics , questionnaires , health examination , and laboratory test to assess the health and nutritional status of korean ( ministry of health and welfare , 2014 ) .
it uses a complex , multistage , probability sampling design to enable estimations to be representative of korean population .
this study analyzed adult subsamples ( 18 yr old ) with sociodemographic information , physical activity questionnaire , and health examination data ( n=19,831 ) .
socioeconomic status was measured using education level ( elementary graduate or lower vs. middle school graduate vs. high school graduate vs. college graduate or higher ) and household income quartiles ( oakes and kaufman , 2006 ) . in this study ,
metabolic syndrome was defined as having three or more of the following conditions ( grundy et al . , 2004 ) : elevated fasting glucose ( 110 or under treatment ) , central obesity ( waist circumference90 cm for male , 85 cm for female ) , systemic hypertension ( systolic blood pressure>130 mmhg or diastolic blood pressure>85 mmhg ) , elevated triglycerides ( 150 ml / dl ) , diminished high - density lipoprotein ( 40 ml / dl for male , 50 ml / dl for female ) physical activity adherence was defined as meeting minimum criterion of the who s ( 2010 ) global physical activity recommendation : 150 min of moderate - intensity physical activity , 75 min of vigorous - intensity physical activity , or an equivalent volume of moderate- to vigorous - intensity physical activity ( i.e. , 600 mets - min / wk ) .
physical activity was measured using international physical activity questionnaire ( ipaq ; fogelholm et al . , 2006 ) .
validity of korean version of the questionnaire was established by previous studies ( chun , 2012 ; oh et al . , 2007 ) .
sex- and age - group - specific physical activity adherence disparities controlling for age were analyzed using adjusted wald - test .
knhanes is a continuous annual surveillance system that consists of demographics , questionnaires , health examination , and laboratory test to assess the health and nutritional status of korean ( ministry of health and welfare , 2014 ) .
it uses a complex , multistage , probability sampling design to enable estimations to be representative of korean population .
this study analyzed adult subsamples ( 18 yr old ) with sociodemographic information , physical activity questionnaire , and health examination data ( n=19,831 ) .
socioeconomic status was measured using education level ( elementary graduate or lower vs. middle school graduate vs. high school graduate vs. college graduate or higher ) and household income quartiles ( oakes and kaufman , 2006 ) . in this study ,
metabolic syndrome was defined as having three or more of the following conditions ( grundy et al . , 2004 ) : elevated fasting glucose ( 110 or under treatment ) , central obesity ( waist circumference90 cm for male , 85 cm for female ) , systemic hypertension ( systolic blood pressure>130 mmhg or diastolic blood pressure>85 mmhg ) , elevated triglycerides ( 150 ml / dl ) , diminished high - density lipoprotein ( 40 ml / dl for male , 50 ml / dl for female ) physical activity adherence was defined as meeting minimum criterion of the who s ( 2010 ) global physical activity recommendation : 150 min of moderate - intensity physical activity , 75 min of vigorous - intensity physical activity , or an equivalent volume of moderate- to vigorous - intensity physical activity ( i.e. , 600 mets - min / wk ) .
physical activity was measured using international physical activity questionnaire ( ipaq ; fogelholm et al . ,
validity of korean version of the questionnaire was established by previous studies ( chun , 2012 ; oh et al . , 2007 ) .
sex- and age - group - specific physical activity adherence disparities controlling for age were analyzed using adjusted wald - test .
statistical significance test for adjusted wald - test was set at 0.05 . using stata 12.1 ( statacorp lp . , college station , tx , usa )
korean adults metabolic syndrome prevalence rate was 32.62% ( 95% ci , 31.6433.61 ) in 20102012 .
physical activity adherence rate of korean adult during this period was 36.87% ( 95% ci , 35.7538.01 ) . among patients with and without metabolic syndrome , the proportion of people who met the who physical activity guideline were 36.28% ( 95% ci , 34.4538.16 ) and 37.96% ( 95% ci , 36.6439.29 ) , respectively .
sex- and age - group - specific metabolic syndrome prevalence rate and metabolic syndrome patients physical activity adherence rate estimation are presented on tables 1 and 2 , respectively .
metabolic syndrome patients physical activity adherence rate of the first ( lowest ) , second , third , and fourth quartile household income group were 28.31% ( 95% ci , 26.1430.28 ) , 34.68% ( 95% ci , 32.7136.70 ) , 37.44% ( 95% ci , 35.6639.25 ) , and 43.79% ( 95% ci , 41.8545.75 ) , respectively .
controlling for age and sex , adherence rate of the fourth income quartile group was statistically significantly higher than the first [ f(1 , 551)=9.45 , p=0.002 ] , second [ f(1 , 551)=8.64 , p=0.003 ] , and third quartile income groups [ f(1 , 551)=6.15 , p=0.013 ] .
this means that metabolic syndrome patients with higher income were more likely to adhere to the physical activity guidelines .
physical activity adherence rate of metabolic syndrome patients with elementary or lower , middle - school , high - school , and college or higher education degree were 25.17% ( 95% ci , 22.9527.54 ) , 38.20% ( 95% ci , 35.1341.00 ) , 39.60% ( 95% ci , 38.2441.77 ) , and 36.89% ( 95% ci , 35.7738.03 ) , respectively . controlling for age and sex , adherence rate of the least educated group was statistically significantly lower than middle school [ f(1 , 551)=13.55 , p<0.001 ] , high school [ f(1 , 551)=11.31 , p<0.001 ] , and college or higher education degree groups [ f(1 , 551)=8.00 , p=0.005 ] .
this shows that disadvantaged social group in terms of education were less likely to meet the minimum levels of the physical activity guidelines .
sex- and age - group - specific physical activity adherence rate by income and education level is presented on tables 3 and 4 , respectively .
this study investigated disparities in physical activity adherence rate among metabolic syndrome patients using 20102012 knhanes data .
overall , it was found that physical activity inequity by income and education level does exist among metabolic syndrome patients . also , there were sex- and age - group - differences in the inequity patterns .
as shown in table 1 , metabolic syndrome prevalence rate was higher in older groups compared to younger counterparts , and such trend was stronger in females than males . even though physical activity is important to prevent progression of cardiovascular disease and type-2 diabetes in these population , adherence rate to the who physical activity recommendation is far less than ideal ( 31.90%44.33% among middle - age group ; 19.68%30.14% among older adults ) .
the implication of this finding is twofold : ( a ) physical inactivity may contribute to increased metabolic syndrome prevalence ; and ( b ) patients with metabolic syndrome do not participate in the generally recommended amount physical activity for health .
sex- and age - group - specific analyses of physical activity disparities by household income and education level ( tables 3 and 4 ) suggest that lower income groups of middle age ( 4064 yr old ) and older group s ( 64 yr old or older ) adherence rate were significantly lower than higher income and/or education groups . among younger adults ( 1839 yr old ) ,
elementary and middle school education has been mandatory in korea since 1985 , so very small fraction of population belong to  elementary or less 
this may have contributed to the inflated standard error of estimation of the adherence rate in these subgroups .
research on health inequity showed that socioeconomic inequity affects onset of chronic diseases ( kim and kim , 2007 ; lim et al . , 2011 ) .
this study added to the past research findings that physical activity as a treatment of such conditions to prevent further development may be unequal across different socioeconomic groups .
future study should further explore psychosocial and biological mechanisms by which physical activity disparities affect incidence rates of cardiovascular diseases and type-2 diabetes among metabolic syndrome patients .
meanwhile , research has shed lights on health disparities in developed countries , because it is an important index of social justice ( kim and kim , 2007 ) .
health inequity directly affects health status of lower socioeconomic group of a society by lower quality of built and social environment , elevated behavioral risk factors , limited access to health care system , and psychological stress ( berkman et al . , 2014 ) .
declined social welfare causes social conflict , psychosocial stress , and consequently health status of the whole society members ( wilkinson , 2002 ) .
therefore , not only lower but also higher socioeconomic groups may be at risk for chronic diseases when socioeconomic equity is impaired . according to kim and kim ( 2007 ) , socioeconomic disparities in korean adults affected not only health outcomes but also health behaviors as mediators by which such social conditions affect health outcomes . according to yang et al .
( 2005 ) , in addition , there were differences in korean adults physical activity level by their socioeconomic status in 2001 .
the current study findings suggest that physical activity disparities have not been alleviated during 20012012 . therefore
, reducing health inequity by promoting physical activity in lower socioeconomic group is still a public health priority
. limitations of this study include cross - sectional survey design , subjective measure of physical activity , and relatively simplistic measure of socioeconomic status .
due to cross - sectional design , this study results do not support cause - and - effect inferences .
ipaq is a 7-day recall subjective measure of physical activity , which is vulnerable to recall bias and social justice bias .
also , ipaq does not capture physical activity of daily life , but to what extent the participant was physically active during the past 7 days .
measures of socioeconomic class in recent studies in health sociology include not only income and education but also community - based indicators such as quality of living place ( berkman et al . , 2014 ) .
 physical activity plays an important role in preventing further progression of metabolic syndrome conditions to cardiovascular disease and type-2 diabetes . 
 this study investigated physical activity disparities by socioeconomic status among metabolic syndrome patients . the fifth korea national health and nutrition examination survey ( 20102012 ) data were analyzed ( n=19,831 ) . 
 a revised definition of the us national cholesterol education program adult treatment panel iii was used for screening metabolic syndrome patients . using international physical activity questionnaire , 
 physical activity adherence was defined as participating in 150 + minutes of moderate - intensity physical activity , 75 + minutes of vigorous - intensity physical activity , or an equivalent combination of moderate - to vigorous - intensity physical activity per week . 
 socioeconomic status was measured by level of education and house - hold income . among metabolic syndrome patients , physical activity adherence rate of first ( lowest ) , second , third , and fourth quartile house - hold income group were 28.31% ( 95% confidence interval [ ci ] , 26.1430.28% ) , 
 34.68% ( 95% ci , 32.7136.70 ) , 37.44% ( 95% ci , 35.6639.25 ) , and 43.79% ( 95% ci , 41.8545.75 ) . 
 physical activity adherence rate of groups with elementary or lower , middle - school , high - school , and college or higher education degree were 25.17% ( 95% ci , 22.9527.54 ) , 38.2% ( 95% ci , 35.1341.00 ) , 39.60% ( 95% ci , 38.2441.77 ) , and 36.89% ( 95% ci , 35.7738.03 ) , respectively . 
 this study found that physical activity adherence rate was lower in socioeconomically disadvantaged metabolic syndrome patients , which may aggravate health inequity status of korean society . 
INTRODUCTION
MATERIALS AND METHODS
Data source
Measures
Statistical analyses
RESULTS
DISCUSSION