despite conspicuous advances and improvements in child health , malnutrition still remains one of the main public health challenges in iran and some other developing countries ( 1 ) . in the year 2011 , almost 6.9 million children under 5 years died worldwide , a large proportion of deaths being related to increased susceptibility to illnesses due to undernutrition ( 2 ) . malnutrition has decreased in asia ( 3 ) affecting preschool children from 16.0% in china to 64.0% in bangladesh ( 4 ) . globally , it is estimated that childhood stunting ( short stature for age ) reduced from 34% to 27% and underweight from 27% to 22% , between 1990 and 2000 ( 5 ) and stunting is predicted to reduce to 22% by the next decade . however , evidence shows that global estimates can not be used to monitor progress at regional level ( 6 ) . anthropometry is an easy tool for assessing nutritional status in individuals and communities and offers the advantages of objective evidence with relatively low technology . the childhood malnutrition is complex and the etiology involves biological , cultural , and socioeconomic influences ( 7 ) . consequently , secular growth differences among ethnic groups have been seen in the united states ( 8) . the role of genetic factors on the secular growth was shown in sri lankan australian children ( 9 ) using free fat mass ( ffm ) instead of body mass index ( bmi ) in filed studies ( 10 ) . of 1,700,000 populations in golestan province ( north of iran ) , 43.9% and 56.1% are living in urban and rural area , respectively . the main job of rural population is agriculture and different ethnic groups such as fars - natives , turkmans and sistanis are living in this region ( 12 ) . beside obesity , under nutrition and growth failure are the health problems in iranian children ( 13 ) . this study was conducted to compare the nutritional status of under - five children among three ethnic groups ( fars - native , turkman and sistani ) during 15 years . this is carried out in a three steps study in rural area in golestan province ( south east of caspian sea ) . data on children with under nutrition trends will help to establish a proper prevention program . the first study was conducted on 2339 children in 2004 ( 14 ) , the second on 2749 children in 1998 ( 13 ) , and the third study on 2487 children in 2013 . 20 out of 118 villages were chosen by random sampling and all of under - five - children enrolled in the study . the sample villages were constant in all three studies . with resumption of 40% rate ( 13 ) , a confidence level of 95% and a maximum marginal error of about 0.02 , anthropometric measurements of the children were performed in light dress and without shoes in the morning . body - weight was measured to the nearest 0.1 kg using a balanced - beam scale , and height was measured to the nearest 0.5 cm while standing up with head , back , and buttock on the vertical band of the height - gauge . the height of children , who were not able to stand , was measured in lying posture . in this study , children s anthropometric data were compared with those in centers for disease control and prevention ( cdc ) reference population , which has been approved by who . the parameters used for body index were the following : weight - for - age as the present nutrition indicator or underweight , height - for - age as the past nutrition indicator or stunting , weight - for - height as the present and past nutrition indicator or wasting . z - score was used for nutritional classification with following category : normal : z>=  -1 sd , slight malnutrition : -1 sd z= < -2 sd , medium malnutrition:-2 sd z=< -3 sd , acute malnutrition z < -3 sd . under nutrition was defined as underweight , stunting and wasting lower than -2 sd ( z < -2 sd ) ( 15 ) . the subjects were divided into three ethnic groups : 1 ) fars - native : the original inhabitants of the fars province , recognized with the same name in the society , 2 ) turkman : the inter marriage of this ethnic group with other ethnic groups happens seldom , so that this ethnic group can be considered as a pure race , 3 ) sistani : this ethnic group immigrated from sistan - beluchestan province from east iran far earlier . economic status was categorized based on possession of 16 consumer items considered necessary for modern day - life . according to this list , the economic status of the sample population was : low  6 , moderate = 7 - 10 , and good = 11 - 16 . according to regular education in iran , educational level was categorized in three groups : 1 ) uneducated , 2 ) 1 - 12 years schooling and 3 ) college graduate . chi squared test was used for qualities of the groups and p value under 0.05 indicated significance rate . logistic regression analysis was applied to estimate the odds ratio ( or ) of under nutrition in genders , ethnic groups , economic status , and paternal education level . children , whose mothers did not agree with participation of their children in the study , were excluded . the studies were approved by ethical research committee of golestan university of medical sciences ( g - p-35 - 1112 ) . table 1 shows the sex and ethnicity distribution of subjects in the three stages of the study . 1685 ( 22.2% ) cases were fars - natives , 2917 ( 38.5% ) turkmans and 2973 ( 39.3% ) sistanis . economic status was 22.9% in low , 52.4% in moderate and 24.7% in good level . poor economic status and low levels of education were seen more in sistani families than in other ethnic groups . the prevalence of underweight ( weight - for - age ) regarding ethnicity and gender in the three stages are presented in table 2 . underweight has increased 0.5% and 3.2% in fars - natives and turkmans while decreased 0.9% in sistanis . statistical difference in the three studies in turkman children is significant ( p = 0.001 ) . the prevalence of underweight in 2013 , was 5% ( 4.8% in boys and 5% in girls ) , 7% ( 8.1% in boys and 5.9% in girls ) and 7.3% ( 7.4% in boys and 7.1% in girls ) in fars - natives , turkmans and sistanis , respectively . in this 15 year - period , underweight in turkman children was seen more in boys than in girls ( 4.2% vs. 2.4% ) while in sistani children , it was reverse ( 0.7% vs. 1.2% ) . table 3 shows the distribution of stunting ( height - for - age ) in the three stages of the study according to ethnicity and gender . stunting has decreased 28.7% and 35.1% in fars - natives and sistanis respectively while it increased 9.3% in turkmans . the trend of under nutrition is statistically significant in all of the studied ethnic groups ( p = 0.001 for all ) . the prevalence of stunting in 2013 in fars - natives was 10.9% ( 11.4% in boys and 10.3% in girls ) , in turkmans 16.3% ( 16.6% in boys and 15.9% in girls ) and 18.4% ( 1 8.8% in boys and 18.1% in girls ) in sistanis . in fars - natives the decrease in stunting in girls ( 30.7% ) was more remarkable compared to boys ( 26.6% ) in contrary to sistani children ( 30.6% vs. 39% ) . variation of stunting was seen more in boys than in girls in turkman group ( 9.5% vs. 7.1% ) . distribution of wasting ( weight - for - height ) in the three stages with regard to ethnicity and gender is presented in table 4 . as can be seen , wasting has increased 2.9% in fars - natives and 2.3% in sistanis while it has decreased 1.3% in turkmans . the trend of stunting is statistically significant in the three stages of the study in all groups ( p < 0.05 for all ) . the prevalence of wasting in 2013 , in fars - natives was 3.5% ( 3.9% in boys and 3.0% in girls ) , in turkmans 1.4% ( 1.9% in boys and 0.8% in girls ) and in sistanis 3.6% ( 3.2% in boys and 3.9% in girls ) . ( % ) . generally , stunting has declined 17.1% ( 17.0% in boy , 17.4% in girl ) while underweight and wasting have increased 0.9% ( 1.1% in boys and 0.6% in girls ) and 1% ( 1.2% in boys and 0.8% in girls ) , respectively during 15 years ( 1998 - 2013 ) . compared with good economic group , the or was 1.831 in poor economic group ( p = 0.001 ) . the risk of malnutrition in sistani ethnic group was 1.754 times more than in fars - natives group ( p = 0.001 ) . the or relating genders and educational level was not significant in turkmans compared with fars - natives ( table 5 ) .   confidential interval 95% . the small decrease in under nutrition existed in fars - native and turkman children from 1998 to 2004 and then increased from 2004 to 2013 while in sistanis a steady reduction was seen during the 15-year - period . stunting dropped in fars - natives and turkmans from 1998 to 2004 and then increased from 2004 to 2013 . during the analyzed period , stunting declined to half in sistani children ( figure 1 ) . a , height - for - age ; b , and weight - for - height ; c , in the three studies in rural area in north iran . underweight in 6.3% , stunting in 15.7% , and wasting in 2.7% of subjects was seen in 2013 with a higher rate in boys . according to unicef report , the prevalence of underweight , stunting , and wasting among iranian five - year olds was 11% , 15% , and 5% , respectively . in iran , several studies have found the prevalence of underweight , stunting and wasting 4.3% , 8.7% , and 7.5% in west azarbaijan province ( 16 ) and 7.5% , 12.5% , and 4.4% in khorasan province ( 17 ) . worldwide about 50% of preschool children are malnourished ranging from 64.0% in bangladesh to 16.0% in china ( 18 ) . in sixty countries with data since 2006 , the median prevalence of wasting is 7.1% , ranging from 0.6% in peru to 21% in the last survey in sudan ; very high rates of wasting are also observed in niger ( 15.5% ) , chad ( 15.6% ) , bangladesh ( 17.5% ) , and india ( 20.0% ) ( 19 ) . the prevalence of underweight , stunting and wasting among under - five - children in rural areas in china was 14.6% , 7.2% and 3.1% , respectively ( 20 ) . these were 4.5% , 8.5% and 3.9% in portuguese ( 21 ) , and 27% , 37% , and 6% in kenya ( 22 ) . compared with our findings , stunting is notable in north iran and it is necessary to establish a control planning . similar to other studies ( 22 , 23 ) , we found sex differences of under nutrition indicating higher rates in boys . in the present study , although the index has decreased in fars - natives and sistanis , in turkmans it has increased . the underweight has been unchanged in fars - natives and in sistani but it has doubled in turkmans during 15 years . stunting has decreased 28.7% in fars - natives and 35.1% in sistanis while it has increased up to 8.5% in turkman children . trend studies on community nutrition of ethnic groups are scarce while studies on overall trends have been established in some countries . globally , childhood stunting decreased from 34% to 27% and underweight decreased from 27% to 22% between 1990 and 2000 ( 3 ) . stunting is predicted to reduce up to 22% by the next decade ( 6 ) . underweight declined significantly from 25.1% in 1993 to 15.1% in 2008 in ghana ( 24 ) . in china ( 15 ) the prevalence of underweight and stunting among under - five children lowered by 24.4% in 2002 to 30.8% , in 2006 . in peru ( 25 ) underweight dropped from 10.1% to 8.2% during 15 years and stunting decreased 19.6% in those children . in india ( 26 ) , a steady decrease in stunting was seen among rural children in 1992 - 2005 , while the decline in underweight was greater between 1992 and 1998 than between 1998 and 2005 . based on unicef report , trends in stunting among under - five children in 1990s have been decreased in china ( 27 ) . in kenya ( 28 ) , child under nutrition based on underweight has declined in most socio - demographic groups during 1993 to 2009 . in that study , stunting was unchanged altogether , although this trend in boys aged 0 - 35 months significantly decreased and in girls aged 12 - 23 months significantly increased . factors associated with under nutrition reported in some studies ( 20 , 26 , 29 ) , are family income , provision of primary health care , low birth weight , gender , age , birth order , religion , maternal age , and maternal education . association between socio - economic status and nutritional condition of ethnic groups has been reported differently in north iran ( 30 , 31 ) . in our study , the lowering trend of under nutrition in fars - natives and sistani children is in line with other studies but growing trend of it in turkmans is unexpected . the social - behaviors in turkman society differ from other ethnic groups in north iran ; possibly there are underlying factors for different food - behavior in this group . the role of food - behaviors of ethnicities residing in north iranian should be evaluated in further studies . consistent with following studies , we have shown the poor economic status as a risk factor for malnutrition . cultural status , income level , food behavior , and less health care were known as the risk factors for malnutrition ( 32 ) . block ( 33 ) believed that low income families are less aware of their food needs . in iran ( 34 ) , socio - demographic factors influence nutritional education with improving health criteria . thereby , more common under nutrition in sistani children may be related to the poor economic status in this ethnic group . the socio - demography related factors as underlying causes of malnutrition in under - five - year children have been highlighted in our study . we did nt evaluate all of the factors that are associated with nutritional status , e.g. quality and quantity of food intake , or physical activities . initially , ethnic groups have not been considered in sample size estimation , and age groups have not been compared among the three studies . .   under nutrition remains one of the health problems in under - five - year children in north iran . generally , under nutrition has declined from 1998 to 2004 while it has risen from 2004 to 2013 . physical growth in three studied ethnic groups is not similar . stunting in sistani children deeply decreased while in turkman children slightly increased during this study . further studies are necessary to evaluate the growth monitoring and socio - demography related factors on children of the three ethnic groups .
background : despite improvements in child health , malnutrition still remains one of the main public health challenges in iran.objectives:the aim of this study was to compare under nutrition among under - five children with regard to ethnicity in rural area in north iran.patients and methods : in three cross - sectional studies 7575 subjects in three time - periods including 2339 children in 1998 , 2749 in 2004 , and 2487 in 2013 , were evaluated . 
 all under - five - children in 20 out of 118 villages were chosen by random sampling and assessed . under nutrition 
 was defined as underweight , stunting and wasting lower than -2 sd ( z < -2 sd).results : generally , stunting was declined 17.1% and underweight and wasting were increased 0.9% and 1% , respectively during 15 years ( 1998 - 2013 ) . 
 underweight increased 0.5% in fars - natives and 3.2% in turkmans and it was decreased 0.9% in sistanis . 
 statistical difference in turkman children among the three stages of the study was significant ( p = 0.001 ) . 
 stunting has decreased 28.7% in fars - natives and 35.1% in sistanis , it was increased 9.3% in turkman group . 
 statistical differences among three stages in inter - ethnic groups were significant ( p = 0.001 for all ) . compared the group with good economic status , the odds ratio was 1.831 in poor economic group ( p = 0.001 ) . 
 the risk of under nutrition in sistanis was 1.754 times more than in fars - natives ( p = 0.001).conclusions : under nutrition remains one of the main health problems in under - five - year children in north iran being more common in sistani children . stunting in sistani children deeply decreased while in turkman children slightly increased during the 15-year period study . 
 poor economic status is a risk factor for under nutrition in this area .