Duration of breast-feeding and cardiovascular risk factors among Iranian children and adolescents: The CASPIAN III study

Abstract

Objectives

Studies examining the relationship between breast-feeding (BF) duration and cardiovascular disease (CVD) risk factors have reached contradictory results. This study aims to investigate the relationship between BF duration and CVD risk factors in adolescents.

Methods

This national population-based study was conducted among 5258 Iranian students, ages 10 to 18 y living in central cities of 27 provinces of Iran. Association was examined between duration of BF and adolescent blood pressure, overweight, obesity, and fasting blood glucose and lipid profiles. Analyses were adjusted for potential confounders.

Results

Low birth weight was less frequent in the longer than in the shorter BF duration categories (P < 0.0001). Number of children was lower in individuals with longer BF duration (P = 0.01). Individuals with longer BF duration used more homemade food than those with shorter BF duration (P < 0.0001). Means of total cholesterol and systolic blood pressure were lower in participants with the longest BF period compared with those with the shortest BF duration; this difference was marginally significant (P = 0.06). No significant association was found between BF duration and CVD risk factors in logistic regression after adjustment for potential confounders.

Conclusions

Although the long-term benefits of BF on preventing CVDs are well documented, controversies exist as to the association of BF duration with such beneficial effects. In this study, there was no substantial evidence that longer BF duration was protective against CVD risk factors among adolescents. More prospective studies are recommended to clarify this association.

Introduction

Cardiovascular disease (CVD) risk factors such as high blood pressure (BP), dyslipidemia, and obesity are increasing both in developed and developing countries [1], [2], [3]. The metabolic risk factors are up to sevenfold higher in obese adolescents [4]. According to a report of 4928 Iranian subjects, ages 15 to 65 y, prevalence of CVD risks including diabetes, hypertension, and dyslipidemia were 5.5%, 28%, and 67%, respectively, in 2009 [5]. The corresponding figures are also considerably high among Iranian children and adolescents; in our previous national survey of 6 to 18 y old students, the most prevalent CVD risk factors were low high-density lipoprotein cholesterol (HDL-C; 28%), followed by hyper-triglyceridemia (20.1%), and overweight (17%) [6]. Based on observational surveys, the risk factors of CVD are rapidly increasing, both in Iranian adults [2] and adolescents [7]. A growing body of evidence suggests that CVD is affected by exposure factors in early life [8], [9], [10]. Human milk feeding is an important factor that has been associated with reduced CVD risks [11], [12]. Based on World Health Organization (WHO) recommendations, exclusive breast-feeding (BF) must be followed at least 6 mo and continued for 2 y. It has been suggested that BF protect against infections and allergy [13]. Additionally, human milk feeding has possible beneficial effects on obesity [14], dyslipidemia [15], BP [16], [17], and insulin resistance [11]. Human milk feeding tends to be the norm in low- and middle-income countries [18]. But many mothers in these countries stop human milk feeding too early [13]. CVD risks are increasing in these countries [19]. The duration of breast-feeding for 12 and 24 mo is continued 87% and 18%, respectively, in urban areas of north of Iran [20].

Although studies examining the association between human milk feeding and CVD risks are not few, previous studies reached to contradictory results [13], [21], [22]. Several evidences suggest inverse association between BF, serum low-density lipoprotein cholesterol (LDL-C) and triglyceride levels (TG) [22], [23], [24], whereas others did not confirm such relationship [25], [26]. However, the association between human milk feeding and reduced risks for diabetes [13], [27] and high BP [13], [28], [29] is not clear. several studies found no relationship between BF and diabetes [30], [31]. Furthermore, the association between human milk feeding and BP may be affected by confounders and publication bias [21]. The beneficial effects of human milk feeding on reduced risk for childhood obesity are improved by long-term duration of lactation [32]. Furthermore, investigations on long-term initiation of complementary feeding are limited [13] and major evaluations are being conducted in developed countries [33], [34]. Compared with some studies reporting that children with late initiation of complementary feeding have lower rates of obesity [35], [36], recent investigation in 15 to 41 y old individuals from five low- and middle-income countries did not document significant correlation between long-term BF duration and lower risks for CVD, including high BP, diabetes, and obesity in this population [13]. Furthermore, maybe early initiation of complementary feeding has positively correlated with risk for diseases [37]. According to our knowledge, there is no national report with such a large sample size among children and adolescents living in the pediatric population of the Middle East and North Africa (MENA) on the relationship between BF duration and CVD risk factors. In this study, we aim to evaluate the correlation between BF duration and CVD risk factors among a nationally representative sample of Iranian children and adolescents.