- Email: [email protected]
Breast-feeding History and Overweight in Latino Preschoolers
Breast-feeding History and Overweight in Latino Preschoolers Margaret Kersey, MD, MS; Rebecca Lipton, PhD; Monica Sanchez-Rosado, MS, RD, LDN; Jessica Kumar, BA; Ronald Thisted, PhD; John D. Lantos, MD Objective.—Describe the relationship between breast-feeding history and risk of overweight in the preschool years in a sample of primarily Mexican-origin Latinos. Methods.—Children’s breast-feeding history, health history, and demographics were obtained in interviewer-administered questionnaires of a convenience sample of 364 parents of children ages 2–5 in an outpatient clinic waiting room serving a predominantly Mexican immigrant population in a large Midwestern city. Child weight status was determined by weighing and measuring each child and calculating age- and sex-specific body mass index (BMI) percentile using 2000 Centers for Disease Control reference values, with children $95th percentile defined as overweight. Results.—Seventy-six of 364 children (21%) were overweight. Eighty-seven percent of children had been breast-fed. Increased duration of breast-feeding was associated with a linearly decreased risk of overweight in bivariate analysis, ranging from an overweight prevalence of 35% for those never breast-fed to 12% for those breast-fed for at least a year. This inverse relationship remained significant in the smaller sample for which maternal BMI data were available (n 5 127), as each additional month of breast-feeding was associated with a 10% decreased odds ratio (OR) of overweight (adjusted OR 5 0.90; 95% CI 5 0.81, 0.99) after controlling for child’s sex, current age, prematurity, birthweight category, maternal education level, and maternal weight status. Conclusion.—This sample of children of Mexican-origin immigrant families had high rates of overweight at very young ages but also very high rates of breast-feeding. Duration of breast-feeding was strongly and inversely related with prevalence of overweight as a preschooler. KEY WORDS:
breast-feeding; childhood overweight; Latinos
Ambulatory Pediatrics 2005;5:355 358
T
he growing epidemic of childhood overweight disproportionately affects children of Mexican American origin, who are even more likely to be overweight than the general population.1–5 According to the National Health and Nutrition Examination Survey 1999– 2000, 23% of Mexican American children ages 6–11 are overweight compared with 16% of the same age general population and among children ages 2–5, 11% of Mexican American children are overweight, versus 10% of the same age general population.2 Rates of overweight among subpopulations of Mexican American children may be even higher: in a school-based sample of kindergartners from primarily Mexican immigrant families in Chicago (n 5 250), the prevalence of overweight was 23%.6 Breast-feeding has been found to be protective against childhood overweight in several studies,7–9 although other studies have failed to find a link between the two.10–13 A
recent review article found breast-feeding to have a small but persistent protective effect against becoming overweight later in life.14 A recent large retrospective longitudinal study reported that increased duration of breastfeeding was associated with decreased risk of childhood overweight among non-Hispanic whites, but not among Latinos.7 This is despite the fact that rates of breast-feeding initiation and breast-feeding at 6 months among Latino children in the United States closely resemble those of non-Hispanic whites.15,16 Among Mexican Americans, immigrant mothers are even more likely to breast-feed than mothers who are US born.17 The current study aims to describe the relationship between breast-feeding history and risk of overweight in the preschool years in a sample of Mexican American children from immigrant families, who may be at especially high risk of becoming overweight, but who also have very high rates of breast-feeding.
From the Division of General Pediatrics and Adolescent Health (Dr Kersey), University of Minnesota, Minneapolis, Minn; Division of Pediatric Endocrinology (Dr Lipton), University of Chicago, Chicago, Ill; No current academic affiliation (Ms Sanchez-Rosado), formerly at Alivio Medical Center, Chicago, Ill; Departments of Health Studies and Statistics (Dr Thisted); and Robert Wood Johnson Clinical Scholars Program (Drs Kumar and Lantos), University of Chicago, Chicago, Ill. Address correspondence to Margaret Kersey, MD, MS, Division of General Pediatrics and Adolescent Health, University of Minnesota Medical School, Room 260, McNamara Building, 200 Oak St SE, Minneapolis, MN 55455 (e-mail: [email protected]). Received for publication June 8, 2004; accepted December 24 2004.
METHODS
AMBULATORY PEDIATRICS Copyright q 2005 by Ambulatory Pediatric Association
Study Design and Study Population The study consisted of interviewer-administered questionnaires with parents of children ages 2–5 years in an outpatient clinic waiting room. The survey was conducted at an innercity community health center in Chicago that serves a predominantly Mexican-immigrant population. Instrument Development Breast-feeding history was determined with the following questions: 1) ‘‘Was (child’s name) breast-fed?’’ 2) (If
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yes): ‘‘For how many months?’’ 3) ‘‘Is s/he still breastfeeding’’? Child health status measures, including child’s birth weight, gestational age, chronic illnesses, and number of hospitalizations were all by parental report. Demographic information, including parental country of origin, length of time in the United States, level of English proficiency, years of education completed, and family income were also by parental self-report. Questions were written in English, translated into Spanish by native bilingual speakers, and then back-translated by a bilingual speaker who had not seen the original English version to assure accuracy. The items were then iteratively pretested in the field to assure good comprehension for this relatively low-literacy population. Subject Recruitment Research assistants approached parents with young children in the clinic waiting room and told them of an ongoing study ‘‘about child health and nutrition.’’ Parents who met all eligibility criteria (mother or father of a child ages 2–5 years, resided in the same household as the child, and considered themselves Latino) were then asked to participate. Verbal informed consent was obtained. Bilingual, bicultural research assistants conducted anonymous faceto-face interviews in English or Spanish according to parental preference. Interviews were conducted Monday– Friday during regular clinic hours between September 2003 and March 2004. Parents were given a small toy for their child for participating in the study. The Institutional Review Boards at the University of Chicago and Alivio Medical Center approved the study. Participants Of the 505 potential subjects who met the eligibility criteria, 416 (82%) agreed to participate. Of those, 366 (88%) interviews contained enough data to be included in the analysis, while the remaining 50 (12%) were discarded due to missing data about child’s height, weight, or breastfeeding history. Two additional interviews were excluded from analysis because the child had a chronic medical condition that would likely affect growth: 1 child had heart disease and 1 had kidney disease; both had multiple hospitalizations. The final sample consisted of 364 subjects. Anthropometric Measures Each child was weighed and measured on the clinic scale and stadiometer and age- and sex-specific body mass index (BMI) percentile was determined using 2000 Centers for Disease Control reference values.18 Children at or above the 95th age- and sex-specific BMI percentile were considered overweight and children less than the 95th percentile were considered nonoverweight in accordance with US Department of Health and Human Services recommendations.19 Maternal and paternal height and weight were determined by self-report, although these were recorded for only 204 of 364 mothers (56%) and 169 of 364 fathers (46%).
AMBULATORY PEDIATRICS
Statistical Analysis The primary outcome measure was child weight status, dichotomized at the 95th percentile (overweight vs not). Bivariate associations were determined between demographic and other predictor variables and the outcome (child weight status) using x2 tests for categorical data and t tests for continuous variables with normal distributions. Data were managed and analyzed using SPSS (SPSS, Inc, Version 12.0, Chicago, Ill) and Stata 8.0 (StataCorp, LP, College Station, Tex). Multivariate logistic regression models were constructed with child weight status as the outcome variable and breast-feeding history as the independent variable on the subset of the data for which maternal BMI data were available. The following variables were included in the model based on their potential to confound the relationship between breast-feeding and child weight: the child’s age, gender, prematurity, birth weight, maternal education (3 levels, with no high school as reference), and maternal weight status. RESULTS Child Weight Status Seventy-eight of 364 children (21%) were overweight. Only 9 of 364 children (2%) were less than the 5th percentile (underweight), limiting comparisons in this group. The underweight children were kept in the analysis because the few children with chronic medical conditions that could significantly affect growth had already been excluded. Participant Demographics Participant demographics and child health covariates are shown in Table 1. Ninety percent of respondents were mothers and 10% were fathers. The majority of the mothers (335, or 92%) were born in Mexico, 24 (7%) were born in the United States, with the remainder born in South America (2%), Central America (1%), and Puerto Rico (0.5%). However, because self-described Latino ethnicity was required for study participation, all study participants were Latino regardless of country of birth. Nearly all of the children were US born (88%), with the rest born in Mexico (11%). The median level of maternal education was 9 years. Maternal English proficiency was low, as only 18% of mothers reported speaking English either well or very well, while 81% reported speaking it not very well or not at all. Nearly all surveys (99%) were conducted in Spanish. The median household income was $1100 per month, although only 56% of respondents answered this question. Child Health Status The children in the sample had few reported health problems. Most (78%) had never been hospitalized since birth, 16% had 1 hospitalization, and 6% had 2 or more hospitalizations. Eight percent of children were born prematurely (,37 weeks gestation), and 7% had birth weights less than 2500 g, with no difference between overweight and nonoverweight children (Table 1).
AMBULATORY PEDIATRICS
Breast-feeding History and Overweight in Latino Preschoolers
357
Table 1. Patient Demographics and Health History by Child’s Overweight Status Overweight Children ($95% BMI)* n (%) % male Age in months, mean (SD) % of mothers Mexican born % of children US born Maternal years in US if foreign born, mean (SD) Years maternal education, mean (SD) % born premature (,37 wk gestation) % born with birth weight .4000 g % born with birth weight ,2500 g % with two or more hospitalizations since birth
Nonoverweight Children (,95% BMI)*
Total Sample
76 (21%) 56 42 (11) 93 86
288 (79%) 50 40 (11) 91 89
364 (100%) 51 41 (11) 91 88
8.7 (6.3) 9.0 (2.9) 7 11 4
8.4 (5.6) 9.4 (3.1) 7 12 7
8.5 (5.8) 9.4 (3.1) 7 12 7
5
6
6
*Differences between overweight and nonoverweight children NS for every variable.
History of Breast-feeding
DISCUSSION
Eighty-seven percent of children in this sample were breast-fed, which is a higher rate than the national average of 65% in the United States20 but is similar to the rate in Mexico, which was 92% in the 1999 National Nutrition Survey.21 Increased duration of breast-feeding was associated with decreased risk of being overweight at ages 2–5 years in a linear dose-response relationship (Table 2). Multivariate Analysis A multivariate logistic regression model was constructed to control for likely confounders in the relationship between breast-feeding and later child weight status (Table 3). We used the restricted subsample for whom maternal BMI data were available after excluding mothers who were pregnant or very recently postpartum, because the survey asked for current height and weight (n 5 127). Increased duration of breast-feeding remained significantly associated with a decreased risk of overweight among preschoolers, as each additional month of breast-feeding was associated with a 10% decreased odds ratio (OR) of overweight (adjusted OR 5 0.90; 95%, confidence interval [CI] 5 0.81, 0.99) after controlling for child’s sex, current age, prematurity, birth-weight category, maternal education level, and maternal weight status. Maternal education was also a significant covariate, as an increased level of maternal education was associated with a decreased risk of child overweight.
Table 2. Risk of Childhood Overweight ($95% BMI) by Child’s Breast-feeding History* Breast-feeding History
% Overweight
None (n 5 49) $1 day but ,3 mo (n 5 43) $3 but ,6 mo (n 5 77) $6 but ,12 mo (n 5 92) $12 mo (n 5 103) Total sample (n 5 364)
35 30 22 19 12 21
95% CI (%) 23, 19, 15, 12, 7,
49 45 33 28 19
*Logistic test for trend: P , .01. BMI indicates body mass index.
The prevalence of overweight among preschool children observed here (21%) is far higher than national estimates (10%),2 although only limited conclusions about prevalence can be drawn due to the sampling scheme. This study is unique, however, in that it focuses on a largely homogenous cultural group that is underrepresented in child health and obesity research.22 In this population of low-income Mexican-origin immigrant families, duration of breast-feeding was strongly and inversely related with prevalence of overweight as a preschooler. The findings of the current study conflict with those of a recent national report, which failed to observe the protective effect of breast-feeding for obesity among Latinos.7 One explanation for the differing results is that the larger study combined heterogeneous groups of Latinos of different countries of origin, levels of acculturation, and breastfeeding rates (eg, Puerto Rican mothers are much less likely to breast-feed than Mexican-origin mothers23). Thus, the larger study’s heterogeneous Latino sample had Table 3. Predictors of Childhood Overweight ($95% BMI) Using Restricted Sample (n 5 127) Covariate
AOR
95% CI
Breast-feeding duration in months Male gender* Premature birth (,37 wks)† Birth weight ,2500 gms‡ Birth weight .4000 gms‡ Age in years, per year Maternal education level§ Maternal overweight (BMI 25–29.5)\ Maternal obesity (BMI $ 30)\
0.90 2.05 1.56 ¶ 1.26 1.02 0.43 0.81 1.15
0.81, 0.99 0.72, 5.82 0.15, 16.30 0.27, 0.60, 0.23, 0.25, 0.36,
5.90 1.72 0.80 2.65 3.72
*Reference group: female. †Reference group: full-term gestation ($37 weeks). ‡Reference group: normal weight birth (2500–4000 g). §Ordinal 3 level variable: no high school (HS), some HS, HS graduate. Reference group: no HS. \Reference group: mother not overweight (Body mass index [BMI] , 25). ¶No observations in this cell (no overweight children with birth weight ,2500 g).
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lower overall breast-feeding initiation and duration rates than the Mexican-origin mothers in the present study.
AMBULATORY PEDIATRICS
7.
Study Limitations Only limited data on parental weight status were available because many parents declined to report their weight. In addition, we did not collect data about exclusive breastfeeding, introduction of solids, or detailed child diet and activity measures. It is not possible to determine whether breast-feeding itself led to lower rates of obesity or whether breast-feeding was a marker for parental concerns about nutrition in general, as mothers who breast fed may also have encouraged healthier nutrition habits later in life than mothers who did not breast-feed. Because the sample was clinic based and the survey did not ask about the reason for the child’s visit, it is possible that children may have come to the clinic for overweight-related health problems, thus biasing the prevalence of overweight upward. Generalizability may be limited due to the convenience sample drawn from a single site serving a very homogeneous population.
8.
9.
10.
11.
12.
13.
14.
Implications This group of Mexican-origin Latinos had high rates of overweight at very young ages but also very high rates and cultural acceptance of breast-feeding. This suggests that programs that encourage prolonged breast-feeding may be useful tools in the battle against childhood overweight and obesity in this high-risk population.
15.
16.
17.
ACKNOWLEDGMENTS The authors thank Alivio Medical Center for collaborating in this project, particularly Executive Director Carmen Velasquez and all the families who participated, and Mary Story for her valuable comments. This research was funded by grants from the Robert Wood Johnson Clinical Scholars Program and the Section of General Pediatrics at the University of Chicago.
18.
REFERENCES
20.
1. Alexander MA, Sherman JB, Clark L. Obesity in MexicanAmerican preschool children—a population group at risk. Publ Health Nurs. 1991;8:53–58. 2. Ogden CL, Flegal KM, Carroll MD, Johnson CL. Prevalence and trends in overweight among US children and adolescents, 1999–2000. JAMA. 2002;288:1728–1732. 3. Strauss RS, Pollack HA. Epidemic increase in childhood overweight, 1986–1998. JAMA. 2001;286:2845–2848. 4. Trevino RP, Marshall RM Jr, Hale DE, et al. Diabetes risk factors in low-income Mexican-American children. Diabetes Care. 1999;22:202–207. 5. Foreyt JP, Cousins JH. Primary prevention of obesity in Mexican-American children. Ann N Y Acad Sci. 1993;699:137–146. 6. Ariza AJ, Chen EH, Binns HJ, Christoffel KK. Risk factors for
19.
21.
22.
23.
overweight in five- to six-year-old Hispanic-American children: a pilot study. J Urban Health. 2004;81:150–161. Grummer-Strawn LM, Mei Z. Does breastfeeding protect against pediatric overweight? Analysis of longitudinal data from the Centers for Disease Control and Prevention Pediatric Nutrition Surveillance System. Pediatrics. 2004;113:e81–e86. Gillman MW, Rifas-Shiman SL, Camargo CA Jr, et al. Risk of overweight among adolescents who were breastfed as infants. JAMA. 2001;285:2461–2467. Bergmann KE, Bergmann RL, Von Kries R, et al. Early determinants of childhood overweight and adiposity in a birth cohort study: role of breast-feeding. Int J Obes Relat Metab Disord. 2003;27:162–172. Hediger ML, Overpeck MD, Kuczmarski RJ, Ruan WJ. Association between infant breastfeeding and overweight in young children. JAMA. 2001;285:2453–2460. Wolman PG. Feeding practices in infancy and prevalence of obesity in preschool children. J Am Diet Assoc. 1984;84:436– 438. Baranowski T, Bryan GT, Rassin DK, et al. Ethnicity, infantfeeding practices, and childhood adiposity. J Dev Behav Pediatr. 1990;11:234–239. Zive MM, McKay H, Frank-Spohrer GC, et al. Infant-feeding practices and adiposity in 4-y-old Anglo- and Mexican-Americans. Am J Clin Nutr. 1992;55:1104–1108. Arenz S, Ruckerl R, Koletzko B, von Kries R. Breast-feeding and childhood obesity—a systematic review. Int J Obes Relat Metab Disord. 2004;28:1247–1256. Li R, Zhao Z, Mokdad A, et al. Prevalence of breastfeeding in the United States: the 2001 National Immunization Survey. Pediatrics. 2003;111:1198–1201. Ryan AS, Wenjun Z, Acosta A. Breast-feeding continues to increase into the new millennium. Pediatrics. 2002;110:1103– 1109. Romero-Gwynn E, Carias L. Breast-feeding intentions and practice among Hispanic mothers in southern California. Pediatrics. 1989;84:626–632. Kuczmarski RJ, Ogden CL, Grummer-Strawn LM, et al. CDC growth charts: United States. Adv Data. 2000:1–27. Barlow SE, Dietz WH. Obesity evaluation and treatment: Expert Committee recommendations. The Maternal and Child Health Bureau, Health Resources and Services Administration and the Department of Health and Human Services. Pediatrics. 1998; 102:e29. Li R, Ogden C, Ballew C, et al. Prevalence of exclusive breastfeeding among US infants: the Third National Health and Nutrition Examination Survey (Phase II, 1991–1994). Am J Public Health. 2002;92:1107–1110. Gonzalez-Cossio T, Moreno-Macias H, Rivera JA, et al. Breastfeeding practices in Mexico: results from the Second National Nutrition Survey 1999. Salud Publica Mex. 2003;45(suppl 4): S477–S489. Flores G, Fuentes-Afflick E, Barbot O, et al. The health of Latino children: urgent priorities, unanswered questions, and a research agenda. JAMA. 2002;288:82–90. Perez-Escamilla R, Himmelgreen D, Segura-Millan S, et al. Prenatal and perinatal factors associated with breast-feeding initiation among inner-city Puerto Rican women. J Am Diet Assoc. 1998;98:657–663.
breast-feeding; childhood overweight; Latinos
Ambulatory Pediatrics 2005;5:355 358
T
he growing epidemic of childhood overweight disproportionately affects children of Mexican American origin, who are even more likely to be overweight than the general population.1–5 According to the National Health and Nutrition Examination Survey 1999– 2000, 23% of Mexican American children ages 6–11 are overweight compared with 16% of the same age general population and among children ages 2–5, 11% of Mexican American children are overweight, versus 10% of the same age general population.2 Rates of overweight among subpopulations of Mexican American children may be even higher: in a school-based sample of kindergartners from primarily Mexican immigrant families in Chicago (n 5 250), the prevalence of overweight was 23%.6 Breast-feeding has been found to be protective against childhood overweight in several studies,7–9 although other studies have failed to find a link between the two.10–13 A
recent review article found breast-feeding to have a small but persistent protective effect against becoming overweight later in life.14 A recent large retrospective longitudinal study reported that increased duration of breastfeeding was associated with decreased risk of childhood overweight among non-Hispanic whites, but not among Latinos.7 This is despite the fact that rates of breast-feeding initiation and breast-feeding at 6 months among Latino children in the United States closely resemble those of non-Hispanic whites.15,16 Among Mexican Americans, immigrant mothers are even more likely to breast-feed than mothers who are US born.17 The current study aims to describe the relationship between breast-feeding history and risk of overweight in the preschool years in a sample of Mexican American children from immigrant families, who may be at especially high risk of becoming overweight, but who also have very high rates of breast-feeding.
From the Division of General Pediatrics and Adolescent Health (Dr Kersey), University of Minnesota, Minneapolis, Minn; Division of Pediatric Endocrinology (Dr Lipton), University of Chicago, Chicago, Ill; No current academic affiliation (Ms Sanchez-Rosado), formerly at Alivio Medical Center, Chicago, Ill; Departments of Health Studies and Statistics (Dr Thisted); and Robert Wood Johnson Clinical Scholars Program (Drs Kumar and Lantos), University of Chicago, Chicago, Ill. Address correspondence to Margaret Kersey, MD, MS, Division of General Pediatrics and Adolescent Health, University of Minnesota Medical School, Room 260, McNamara Building, 200 Oak St SE, Minneapolis, MN 55455 (e-mail: [email protected]). Received for publication June 8, 2004; accepted December 24 2004.
METHODS
AMBULATORY PEDIATRICS Copyright q 2005 by Ambulatory Pediatric Association
Study Design and Study Population The study consisted of interviewer-administered questionnaires with parents of children ages 2–5 years in an outpatient clinic waiting room. The survey was conducted at an innercity community health center in Chicago that serves a predominantly Mexican-immigrant population. Instrument Development Breast-feeding history was determined with the following questions: 1) ‘‘Was (child’s name) breast-fed?’’ 2) (If
355
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yes): ‘‘For how many months?’’ 3) ‘‘Is s/he still breastfeeding’’? Child health status measures, including child’s birth weight, gestational age, chronic illnesses, and number of hospitalizations were all by parental report. Demographic information, including parental country of origin, length of time in the United States, level of English proficiency, years of education completed, and family income were also by parental self-report. Questions were written in English, translated into Spanish by native bilingual speakers, and then back-translated by a bilingual speaker who had not seen the original English version to assure accuracy. The items were then iteratively pretested in the field to assure good comprehension for this relatively low-literacy population. Subject Recruitment Research assistants approached parents with young children in the clinic waiting room and told them of an ongoing study ‘‘about child health and nutrition.’’ Parents who met all eligibility criteria (mother or father of a child ages 2–5 years, resided in the same household as the child, and considered themselves Latino) were then asked to participate. Verbal informed consent was obtained. Bilingual, bicultural research assistants conducted anonymous faceto-face interviews in English or Spanish according to parental preference. Interviews were conducted Monday– Friday during regular clinic hours between September 2003 and March 2004. Parents were given a small toy for their child for participating in the study. The Institutional Review Boards at the University of Chicago and Alivio Medical Center approved the study. Participants Of the 505 potential subjects who met the eligibility criteria, 416 (82%) agreed to participate. Of those, 366 (88%) interviews contained enough data to be included in the analysis, while the remaining 50 (12%) were discarded due to missing data about child’s height, weight, or breastfeeding history. Two additional interviews were excluded from analysis because the child had a chronic medical condition that would likely affect growth: 1 child had heart disease and 1 had kidney disease; both had multiple hospitalizations. The final sample consisted of 364 subjects. Anthropometric Measures Each child was weighed and measured on the clinic scale and stadiometer and age- and sex-specific body mass index (BMI) percentile was determined using 2000 Centers for Disease Control reference values.18 Children at or above the 95th age- and sex-specific BMI percentile were considered overweight and children less than the 95th percentile were considered nonoverweight in accordance with US Department of Health and Human Services recommendations.19 Maternal and paternal height and weight were determined by self-report, although these were recorded for only 204 of 364 mothers (56%) and 169 of 364 fathers (46%).
AMBULATORY PEDIATRICS
Statistical Analysis The primary outcome measure was child weight status, dichotomized at the 95th percentile (overweight vs not). Bivariate associations were determined between demographic and other predictor variables and the outcome (child weight status) using x2 tests for categorical data and t tests for continuous variables with normal distributions. Data were managed and analyzed using SPSS (SPSS, Inc, Version 12.0, Chicago, Ill) and Stata 8.0 (StataCorp, LP, College Station, Tex). Multivariate logistic regression models were constructed with child weight status as the outcome variable and breast-feeding history as the independent variable on the subset of the data for which maternal BMI data were available. The following variables were included in the model based on their potential to confound the relationship between breast-feeding and child weight: the child’s age, gender, prematurity, birth weight, maternal education (3 levels, with no high school as reference), and maternal weight status. RESULTS Child Weight Status Seventy-eight of 364 children (21%) were overweight. Only 9 of 364 children (2%) were less than the 5th percentile (underweight), limiting comparisons in this group. The underweight children were kept in the analysis because the few children with chronic medical conditions that could significantly affect growth had already been excluded. Participant Demographics Participant demographics and child health covariates are shown in Table 1. Ninety percent of respondents were mothers and 10% were fathers. The majority of the mothers (335, or 92%) were born in Mexico, 24 (7%) were born in the United States, with the remainder born in South America (2%), Central America (1%), and Puerto Rico (0.5%). However, because self-described Latino ethnicity was required for study participation, all study participants were Latino regardless of country of birth. Nearly all of the children were US born (88%), with the rest born in Mexico (11%). The median level of maternal education was 9 years. Maternal English proficiency was low, as only 18% of mothers reported speaking English either well or very well, while 81% reported speaking it not very well or not at all. Nearly all surveys (99%) were conducted in Spanish. The median household income was $1100 per month, although only 56% of respondents answered this question. Child Health Status The children in the sample had few reported health problems. Most (78%) had never been hospitalized since birth, 16% had 1 hospitalization, and 6% had 2 or more hospitalizations. Eight percent of children were born prematurely (,37 weeks gestation), and 7% had birth weights less than 2500 g, with no difference between overweight and nonoverweight children (Table 1).
AMBULATORY PEDIATRICS
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Table 1. Patient Demographics and Health History by Child’s Overweight Status Overweight Children ($95% BMI)* n (%) % male Age in months, mean (SD) % of mothers Mexican born % of children US born Maternal years in US if foreign born, mean (SD) Years maternal education, mean (SD) % born premature (,37 wk gestation) % born with birth weight .4000 g % born with birth weight ,2500 g % with two or more hospitalizations since birth
Nonoverweight Children (,95% BMI)*
Total Sample
76 (21%) 56 42 (11) 93 86
288 (79%) 50 40 (11) 91 89
364 (100%) 51 41 (11) 91 88
8.7 (6.3) 9.0 (2.9) 7 11 4
8.4 (5.6) 9.4 (3.1) 7 12 7
8.5 (5.8) 9.4 (3.1) 7 12 7
5
6
6
*Differences between overweight and nonoverweight children NS for every variable.
History of Breast-feeding
DISCUSSION
Eighty-seven percent of children in this sample were breast-fed, which is a higher rate than the national average of 65% in the United States20 but is similar to the rate in Mexico, which was 92% in the 1999 National Nutrition Survey.21 Increased duration of breast-feeding was associated with decreased risk of being overweight at ages 2–5 years in a linear dose-response relationship (Table 2). Multivariate Analysis A multivariate logistic regression model was constructed to control for likely confounders in the relationship between breast-feeding and later child weight status (Table 3). We used the restricted subsample for whom maternal BMI data were available after excluding mothers who were pregnant or very recently postpartum, because the survey asked for current height and weight (n 5 127). Increased duration of breast-feeding remained significantly associated with a decreased risk of overweight among preschoolers, as each additional month of breast-feeding was associated with a 10% decreased odds ratio (OR) of overweight (adjusted OR 5 0.90; 95%, confidence interval [CI] 5 0.81, 0.99) after controlling for child’s sex, current age, prematurity, birth-weight category, maternal education level, and maternal weight status. Maternal education was also a significant covariate, as an increased level of maternal education was associated with a decreased risk of child overweight.
Table 2. Risk of Childhood Overweight ($95% BMI) by Child’s Breast-feeding History* Breast-feeding History
% Overweight
None (n 5 49) $1 day but ,3 mo (n 5 43) $3 but ,6 mo (n 5 77) $6 but ,12 mo (n 5 92) $12 mo (n 5 103) Total sample (n 5 364)
35 30 22 19 12 21
95% CI (%) 23, 19, 15, 12, 7,
49 45 33 28 19
*Logistic test for trend: P , .01. BMI indicates body mass index.
The prevalence of overweight among preschool children observed here (21%) is far higher than national estimates (10%),2 although only limited conclusions about prevalence can be drawn due to the sampling scheme. This study is unique, however, in that it focuses on a largely homogenous cultural group that is underrepresented in child health and obesity research.22 In this population of low-income Mexican-origin immigrant families, duration of breast-feeding was strongly and inversely related with prevalence of overweight as a preschooler. The findings of the current study conflict with those of a recent national report, which failed to observe the protective effect of breast-feeding for obesity among Latinos.7 One explanation for the differing results is that the larger study combined heterogeneous groups of Latinos of different countries of origin, levels of acculturation, and breastfeeding rates (eg, Puerto Rican mothers are much less likely to breast-feed than Mexican-origin mothers23). Thus, the larger study’s heterogeneous Latino sample had Table 3. Predictors of Childhood Overweight ($95% BMI) Using Restricted Sample (n 5 127) Covariate
AOR
95% CI
Breast-feeding duration in months Male gender* Premature birth (,37 wks)† Birth weight ,2500 gms‡ Birth weight .4000 gms‡ Age in years, per year Maternal education level§ Maternal overweight (BMI 25–29.5)\ Maternal obesity (BMI $ 30)\
0.90 2.05 1.56 ¶ 1.26 1.02 0.43 0.81 1.15
0.81, 0.99 0.72, 5.82 0.15, 16.30 0.27, 0.60, 0.23, 0.25, 0.36,
5.90 1.72 0.80 2.65 3.72
*Reference group: female. †Reference group: full-term gestation ($37 weeks). ‡Reference group: normal weight birth (2500–4000 g). §Ordinal 3 level variable: no high school (HS), some HS, HS graduate. Reference group: no HS. \Reference group: mother not overweight (Body mass index [BMI] , 25). ¶No observations in this cell (no overweight children with birth weight ,2500 g).
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lower overall breast-feeding initiation and duration rates than the Mexican-origin mothers in the present study.
AMBULATORY PEDIATRICS
7.
Study Limitations Only limited data on parental weight status were available because many parents declined to report their weight. In addition, we did not collect data about exclusive breastfeeding, introduction of solids, or detailed child diet and activity measures. It is not possible to determine whether breast-feeding itself led to lower rates of obesity or whether breast-feeding was a marker for parental concerns about nutrition in general, as mothers who breast fed may also have encouraged healthier nutrition habits later in life than mothers who did not breast-feed. Because the sample was clinic based and the survey did not ask about the reason for the child’s visit, it is possible that children may have come to the clinic for overweight-related health problems, thus biasing the prevalence of overweight upward. Generalizability may be limited due to the convenience sample drawn from a single site serving a very homogeneous population.
8.
9.
10.
11.
12.
13.
14.
Implications This group of Mexican-origin Latinos had high rates of overweight at very young ages but also very high rates and cultural acceptance of breast-feeding. This suggests that programs that encourage prolonged breast-feeding may be useful tools in the battle against childhood overweight and obesity in this high-risk population.
15.
16.
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ACKNOWLEDGMENTS The authors thank Alivio Medical Center for collaborating in this project, particularly Executive Director Carmen Velasquez and all the families who participated, and Mary Story for her valuable comments. This research was funded by grants from the Robert Wood Johnson Clinical Scholars Program and the Section of General Pediatrics at the University of Chicago.
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REFERENCES
20.
1. Alexander MA, Sherman JB, Clark L. Obesity in MexicanAmerican preschool children—a population group at risk. Publ Health Nurs. 1991;8:53–58. 2. Ogden CL, Flegal KM, Carroll MD, Johnson CL. Prevalence and trends in overweight among US children and adolescents, 1999–2000. JAMA. 2002;288:1728–1732. 3. Strauss RS, Pollack HA. Epidemic increase in childhood overweight, 1986–1998. JAMA. 2001;286:2845–2848. 4. Trevino RP, Marshall RM Jr, Hale DE, et al. Diabetes risk factors in low-income Mexican-American children. Diabetes Care. 1999;22:202–207. 5. Foreyt JP, Cousins JH. Primary prevention of obesity in Mexican-American children. Ann N Y Acad Sci. 1993;699:137–146. 6. Ariza AJ, Chen EH, Binns HJ, Christoffel KK. Risk factors for
19.
21.
22.
23.
overweight in five- to six-year-old Hispanic-American children: a pilot study. J Urban Health. 2004;81:150–161. Grummer-Strawn LM, Mei Z. Does breastfeeding protect against pediatric overweight? Analysis of longitudinal data from the Centers for Disease Control and Prevention Pediatric Nutrition Surveillance System. Pediatrics. 2004;113:e81–e86. Gillman MW, Rifas-Shiman SL, Camargo CA Jr, et al. Risk of overweight among adolescents who were breastfed as infants. JAMA. 2001;285:2461–2467. Bergmann KE, Bergmann RL, Von Kries R, et al. Early determinants of childhood overweight and adiposity in a birth cohort study: role of breast-feeding. Int J Obes Relat Metab Disord. 2003;27:162–172. Hediger ML, Overpeck MD, Kuczmarski RJ, Ruan WJ. Association between infant breastfeeding and overweight in young children. JAMA. 2001;285:2453–2460. Wolman PG. Feeding practices in infancy and prevalence of obesity in preschool children. J Am Diet Assoc. 1984;84:436– 438. Baranowski T, Bryan GT, Rassin DK, et al. Ethnicity, infantfeeding practices, and childhood adiposity. J Dev Behav Pediatr. 1990;11:234–239. Zive MM, McKay H, Frank-Spohrer GC, et al. Infant-feeding practices and adiposity in 4-y-old Anglo- and Mexican-Americans. Am J Clin Nutr. 1992;55:1104–1108. Arenz S, Ruckerl R, Koletzko B, von Kries R. Breast-feeding and childhood obesity—a systematic review. Int J Obes Relat Metab Disord. 2004;28:1247–1256. Li R, Zhao Z, Mokdad A, et al. Prevalence of breastfeeding in the United States: the 2001 National Immunization Survey. Pediatrics. 2003;111:1198–1201. Ryan AS, Wenjun Z, Acosta A. Breast-feeding continues to increase into the new millennium. Pediatrics. 2002;110:1103– 1109. Romero-Gwynn E, Carias L. Breast-feeding intentions and practice among Hispanic mothers in southern California. Pediatrics. 1989;84:626–632. Kuczmarski RJ, Ogden CL, Grummer-Strawn LM, et al. CDC growth charts: United States. Adv Data. 2000:1–27. Barlow SE, Dietz WH. Obesity evaluation and treatment: Expert Committee recommendations. The Maternal and Child Health Bureau, Health Resources and Services Administration and the Department of Health and Human Services. Pediatrics. 1998; 102:e29. Li R, Ogden C, Ballew C, et al. Prevalence of exclusive breastfeeding among US infants: the Third National Health and Nutrition Examination Survey (Phase II, 1991–1994). Am J Public Health. 2002;92:1107–1110. Gonzalez-Cossio T, Moreno-Macias H, Rivera JA, et al. Breastfeeding practices in Mexico: results from the Second National Nutrition Survey 1999. Salud Publica Mex. 2003;45(suppl 4): S477–S489. Flores G, Fuentes-Afflick E, Barbot O, et al. The health of Latino children: urgent priorities, unanswered questions, and a research agenda. JAMA. 2002;288:82–90. Perez-Escamilla R, Himmelgreen D, Segura-Millan S, et al. Prenatal and perinatal factors associated with breast-feeding initiation among inner-city Puerto Rican women. J Am Diet Assoc. 1998;98:657–663.