Anemia is a major public health problem affecting around 1.62 billion people globally [1, 2]. It is defined as a common blood disorders in which number of red blood cells, or the hemoglobin (Hb) concentration, falls below an established cut-off value, consequently impairing the capacity of the blood to transport oxygen around the body [3]. Anemia may develop at any stage of the life cycle [1] but children, adolescent girls and women of reproductive age are high risk groups for developing anemia [4, 5]. Anemia is a particular concern for adolescent girls i.e., aged 10–19 years [6], as this is a period of intense growth with higher iron requirement. This compounded with frequent menstrual blood losses and inadequate dietary iron intake in this period results in anemia [7]. Though anemia has multifaceted etiology, it primarily results from iron deficiency [3, 7, 8]. Worldwide, about 50% cases of anemia is caused by iron deficiency [9], but based on local conditions, this proportion may vary among population groups and areas [9, 10]. Some other haemopoietic micronutrient deficiencies like folate, riboflavin, Vitamins A and B₁₂ may increase risk for anemia [7]. Infectious diseases such as malaria, tuberculosis and HIV/AIDS can also contribute to anemia, particularly prevalent in Africa and sub- Saharan Africa [4, 7]. Excessive blood loss resulting from hookworm infection and schistosomiasis can also lead to anemia [7, 11]. Some genetic or inherited hemoglobin disorders caused by inherited mutations of the globin genes leading to qualitative and quantitative abnormalities of globin synthesis (sickle-cell disease and thalassemia) also increases the risk for anemia, mainly in Mediterranean and Southeast Asian countries [4, 7, 12]. In Bangladesh more than 7000 children born each year with thalassemia and WHO report estimates that there are about 3% beta-thalassemia carrier and about 4% HB E/beta-thalassemia carrier in Bangladesh [13].

Anemia has serious consequences in adolescence with growth retardation [14] as well as impaired physical and cognitive performance [15]. Iron is also an essential nutrients for the functioning of neurotransmitter having a role in cognition, and in scarcity of hemoglobin, hypoxia develops with decreased cardiac output [16]. Several studies reported that iron supplementation among anemic adolescents and women had a role in cognition [17]. Higher behavioral disturbances along with reduced learning capacities and suboptimal school performance have also been documented among anemic school children [18]. Moreover, adolescent girls with anemia tend to commence their pregnancy with increased risk of morbidities and mortality for both mother and child [10].

Adolescent anemia is mostly prevalent in developing countries [4, 7, 19], and girls are more vulnerable than boys [20]. Studies identified that a large number of adolescent girls of South Asian region including Bangladesh are suffering from anemia along with other forms of malnutrition [21, 22]. Prevalence of anemia ranged from 31.6% to 99.9% among adolescent girls in India [2, 5] while in Nepal, the prevalence was as high as 68.8% [23]. Meanwhile, as of 2000, a study carried out in peri-urban areas of Bangladesh reported that the prevalence of anemia to be 27% among adolescent girls [24]. Recent study reported in 2016 that national prevalence of iron deficiency (serum ferritin level < 15.0 ng/ml) among non-pregnant non lactating women and children aged 12–14 years was 7.1% and 9.5% respectively in Bangladesh. It was found much higher (10%) among the children (12–14 years) in the rural Bangladesh. Furthermore, the study estimated that iron deficiency anemia could be much lower than anticipated among the Bangladeshi population of non-pregnant no lactating women (4.8%) and children aged 12–14 years (1.8%) [25]. However, there are still limited information till date in Bangladesh on the prevalence of anemia among adolescent girls (10–19 years) and its distribution. Other studies revealed the causal factors of anemia such consumption of traditional carbohydrate based diet lacking iron rich animal products, irregular eating habits [2], parent’s education [26], father’s occupation [27], age [19, 28], malaria [28], body mass index [19], menstruation ‘when marked as heavy’ [28], helminthes infestation [19, 28] and post-meal tea consumption [26]. However, all of these studies were carried out outside Bangladesh. This study will shed light on not only the number of adolescents suffering from low blood hemoglobin level but will also provide information on the factors associated with it.

Our study reports the prevalence of anemia and distribution of severity of anemia in different socio-demographic strata among adolescent girls of the age bracket of 10–19 years in Bangladesh. The study further examines the risk factors of anemia among them. While, the prevalence of all form of anemia were found 51.6%, most of them (46%) were mildly anemic and few (5.4%) were moderate with only 0.23% severely anemic. Our study also found that malnutrition, pregnancy status and wealth quintile are significant risk factors of anemia among adolescent girls in Bangladesh.

Prevalence of anemia reported in our study was similarly high to the most recent Bangladesh Demographic and Health Survey (BDHS) where the prevalence of any form anemia were 48.6%, while mild, moderate and severe anemia were 39.2%, 9.4% and 0.0% respectively among adolescent girls of 15–19 years [22]. Though the participants of that survey were married adolescent girls, the findings are comparable as very little difference was observed in terms of anemia status between married and unmarried adolescent girls in our study. Our study is unique in that sense as it covered nationally representative sample of adolescent girls regardless their all socio-demographic variables including marital status, and habitat. Several other similar studies [27, 34, 35] conducted in India also found that girls were mostly suffering from mild to moderate anemia.

Few other studies [24, 36–39] were carried out till date examining the prevalence and risk factors of anemia among adolescent girls in Bangladesh. Most of the studies were outdated and conducted in school setting, while a few were carried out at community level. A study [37] conducted among adolescent girls aged 11–16 years in rural community found that 43.0% of the girls were anemic, which indicates that the situation is as worse as it was previously. School based studies were carried out in urban [38] or per-urban [24] areas and anemia prevalence was ranged from 22 to 27%. Studies [16, 27, 40] conducted in community setting of India also found a very high prevalence of anemia among adolescent girls and it ranged between 48 and 85%. The prevalence was 30.9% in Afghanistan and 58.1% in Sri Lanka [41] and 23% in Iran [42]. Several other studies conducted in sub-Saharan Africa also found high prevalence of anemia among adolescent girls [43].

Several socioeconomic and physiological factors such as literacy [44], father’s occupation [27], lower socio-economic status [35], traditional and irregular feeding habit [2] and lower BMI [45] are reported as the most important factors associated with anemia among adolescent girls. Nutritional deprivation has long been identified as one of the most important causes of anemia, particularly among adolescent girls from underdeveloped countries [28]. Our study identified that malnutrition (BMI-for-age Z-score < −2SD) is a significant risk factor of anemia among adolescent girls. Studies conducted in similar setting also found that lower BMI is associated with higher rate of anemia among adolescent girls [23, 27]. However, contradictory to this, BMI had not significantly been associated with anemia among adolescent girls from rural India [40].

A number of studies affirmed the association between low socio-economic status and anemia among adolescent girls from low and middle income countries [35]. Studies conducted in Bangladesh also clearly demonstrated the influence of poor socio-economic status on higher anemia prevalence and reported that around half of the anemic girls belong to the low socioeconomic status group [36]. Present study pointed that girls from the poorest wealth quintile were more prone to become anemic compared to those from the richest wealth quintile. Adolescent girls of poor socioeconomic condition tends to consume less diversified diet [46] with lesser micronutrient content which might have resulted in lower BMI with concomitant higher prevalence of anemia.

In Bangladesh, adolescent pregnancy is a major social and health concern as 31% of adolescents aged 15–19 was childbearing mother [47]. We also found than non-pregnant adolescent girls were more prone to become anemic compared to that of the pregnant girls. This may mean that non-pregnant adolescent girls would require more attention from different stakeholders, however, prevalence of anemic among pregnant adolescent was still high.

Our study has several strengths over other studies of that kind. It followed a multistage cluster sampling procedure covering a wide region of both rural and urban areas and is generable to the entire population. The biochemical procedure of testing blood hemoglobin level to ascertain anemia is one of the most effective methods of measuring anemia at community setting compared to other methods such as clinical examination. Another advantage is as it is a community based study it provides a population level assessment of anemia prevalence especially severe anemia, which is unlikely to be detected through school-based studies where only school going adolescent are available [27].

However, the study was subjected to certain limitations. Although, the study identified prevalence of anemia it cannot be confirmed whether the anemia is resulting from iron deficiency, as we have no data on dietary iron intake or serum ferritin level. Also, the study was unable to confirm the types and causes of anemia without the data on RBC indices (MCV, MCH, MCHC) and blood plates, which can be measured using Hematology analyzers. Furthermore, as the data was cross-sectional in nature, temporal relationship between the socio-demographics and anemia should be interpreted with caution. However, it is estimated that at least half of anemia worldwide is due to nutritional iron deficiency anemia [10] and 32% anemia in Bangladesh is iron deficiency anemia [24]. However, other research reported a low prevalence of iron deficiency anemia among Bangladeshi women, most of them above the age of adolescence [8]. And although, Bangladesh has a nationwide program to distribute iron and folic acid for pregnant women, no such program exists for adolescent girls. We also did not assess energy, protein or other macro or micronutrient intakes. Studies identified that hookworm infestation is significantly associated with anemia in adolescent girls [19, 40]. But this study did not collect information regarding hookworm infestation. Further studies regarding these issues would enhance our understanding and therefore more work is needed to determine the cause of anemia in these adolescent girls to determine what effective interventions are warranted.

Our study reaffirm the fact that anemia is a major problem for adolescent girls in Bangladesh which need to be given highest priority. Malnourished girls are highly vulnerable to anemia, most of which belong to the poor socioeconomic class. Currently there is actually no large scale intervention focusing on to control anemia among adolescent girls of the country. Thus, it is essential to initiate interventions to improve dietary iron intake along with measures to control infections and infestations which involves unusual blood loss resulting anemia.