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Objectives
The purpose of this research was to describe the physical growth status, bone mineral content, areal bone mineral density, body composition, and metabolic risk level of children of Sudanese immigrant families, and to determine the relationship between these outcome measures and exposure to an adverse environment. Exposure was defined as the time spent in Sudan or neighboring countries and timing was defined as the age a child arrived in the USA. Two major modifying factors were considered; current nutritional status (food quality and food security) and current physical activity levels.
Study Design and Methods
This is a cross-sectional study conducted between July 2011 and April 2012. Subjects were recruited from the Iowa City, Iowa metropolitan area. The sample included 64 children between the ages of five and eighteen; 33 females and 31 males. Physical growth measures included weight, height, and BMI. Bone growth measures (body bone mineral content and areal bone mass density at the hip and spine) and body composition measures (lean mass, fat mass, and body fat percent) were measured using DXA. Metabolic risk factors included fasting blood glucose, low density lipoprotein (LDL), high density lipoprotein (HDL), total cholesterol, triglyceride, and C Reactive Protein (CRP) levels, and Homeostasis Model of Assessment Insulin Resistance (HOMA-IR). Physical activity was measured by self-report physical activity questionnaire for children and adolescents (modified PAQ-A and PAQ-C) and by direct measure using Omron Pedometers (HJ-720 IT). Other collected data included food quality, food security, food frequency, and pubertal development using a puberty developmental scale.
Results
The mean age for all children was 10.1 ± 3.3 years. More than half of the children (n=33, 51.6%) were born in the USA, 14 children (21.9%) were born in Sudan, and the other children were born in other countries. The majority of the children (63.6%) lived in low income households reporting annual income less than USD $19,000.
Over one quarter (26.5%) of the children were overweight or obese as defined by BMI percentile and when categorized by BF%, 35.5% of the girls and 27.3% of the boys were identified as obese. Height stunting was noted with 4.7% severely stunted (more than 2 sd below the mean) and 9.4% moderately stunted (more than 1 sd below the mean).
The mean Z score for FMI and LMI were -0.57 ± 1.51 and 0.49 ± 0.75, respectively, and neither was normally distributed. Around half of the children had FMIZ (53.1%) and LMIZ (47%) scores more than 1 SD below the mean. Median Z scores for all bone measures were negative; BMC, -0.71, hip aBMD, -0.53, and Spine aBMD, -0.13. Around one-third of the children fell more than 1sd below the mean for BMC (38%) and hip aBMD (33%). Metabolic risk factors were elevated in some subjects; high total cholesterol, 23.4%; high triglycerides, 32.8%; low HDL, 19%; high HOMA-IR and CRP levels, 15.6 %.
Forty percent of participating families reported some level of food insecurity, and 31% reported skipping or cutting the size of meals due to inadequate food supplies. Both self-reported questionnaires and data collected from pedometers showed that the majority of study participants were inactive, Wednesday & Thursday were identified as the most active days with activity levels of 52.6% and 50.9%, respectively, and 40% of the study subjects were inactive on weekends. More than half (56.9%) of the subjects reported watching TV more than two hours per day. Children born in the USA had higher rates of height and weight stunting and obesity as compared to children born outside the USA (24%, 37.5%, 32.26%; 3.12%, 25%, 21.21%, respectively). Children born in the USA had lower Z scores in all bone and body composition measures.
Using GEE analysis, longer residence in Sudan was associated with lower WAZ scores (β =-0.16, p= 0.07), and lower LMIZ scores (β =-0.05, p= 0.06). Children with longer residence in Sudan or neighboring countries had higher LDL and HOMA-IR levels (β =2.997, p= 0.0005), and (β =0.03, p= 0.08). Adjusting for gender, girls who spent more time in Sudan had higher triglyceride and CRP levels β =11.9, p=0.027) and (β =0.5, p=0.03), respectively.
Children who were older when they entered the USA had higher HAZ scores (β =0.06, p=0.05). Adjusting for gender, Girls who arrived in the USA at a younger age had lower WAZ scores (β =-0.42, p=0.01), while girls who entered the USA at an older age had higher HOMA-IR, triglyceride, and CRP levels (β =0.29, p=0.005), (β =0.14, p= 0.05) and (β =0.5, p=0.05), respectively.
Adjusting for number of years spent in the USA and physical activity levels, longer residence in Sudan was associated with poorer LMIZ (β =-0.06, p=0.001) and hip aBMD Z scores (β =0.11, p= 0.01). In addition, children who arrived in the USA at a younger age had higher height for age Z scores (β=0.094, p=0.005) and lower LMIZ scores (β =-0.09, p=0.04), respectively.
Conclusion
Sudanese children in the Iowa City metropolitan area, particularly those born in the USA, have low Z scores for physical growth, bone growth, and body composition measures. A significant percent of the children had high triglycerides and total cholesterol levels. The majority of Sudanese children were physically inactive and food insecurity was common.