General description of findings
A total of 50 studies met the inclusion criteria (Figure 1). Data on the prevalence of anemia among indigenous and non-indigenous populations was available from 13 different countries: Australia, Brazil, Canada, Guatemala, India, Kenya, Malaysia, Mexico, New Zealand, Sri Lanka, Tanzania, the United States, and Venezuela. Overall, there was only one nationally representative study, which was conducted in Mexico and received the highest quality rating. Four studies examined populations that were representative of an entire state within a country, such as parts of Australia. Otherwise, the studies sampled from particular areas or communities known to be densely inhabited by or including people from an indigenous population. General limitations included the lack of reporting on anemia definitions in retrospective studies, the absence of confidence intervals around prevalence estimates of anemia, and the lack of statistical significance testing between anemia rates in indigenous and non-indigenous samples.
As might be expected, Hb, the most cost-efficient and commonly used measure to screen for anemia,7 was used to diagnose anemia across studies (Table 3). Among the studies that reported on the definition of anemia that was used, the most commonly used definitions were those suggested by the WHO nearly 40 years ago, which account for age, sex, and pregnancy status.16 Studies have found that Hb values are affected by such variables as sex, age, the race of the individual, altitude, and smoking.16 Adjustments in Hb values were reported for sex, age, pregnancy, and altitude (Table 3). Studies conducted in areas located above sea level recognized the influence of altitude on Hb levels and adjusted the values accordingly. The study by Hinderaker et al.17 in Tanzania adjusted Hb values using a formula that accounts for altitudes above sea level. In Guatemala, the study by Neufeld et al.18 defined anemia as Hb ≤130 g/L at lower altitudes and as Hb ≤134 g/L at higher altitudes.
Variations in the definition of anemia by ethnicity were not considered. While there has been evidence to suggest ethnic differences in the cutoffs for Hb and other biochemical measures, the search for consensus on the strength of this evidence and the appropriate cutoffs to use is ongoing. For example, large-scale studies have conclusively established that North American blacks have a lower population-mean of serum Hb concentrations than North American whites.19 However, these studies have also reported higher erythrocyte sedimentation rates and higher mean serum ferritin levels in the black population, which, in association with low Hb levels, are indicative of anemia due to chronic disease.19 These findings indicate that the difference in Hb concentrations between blacks and whites in the United States is the result of factors other than iron intake and iron status. Higher serum ferritin levels, despite lower Hb levels, may result from a higher prevalence of acute infections and chronic inflammatory diseases, suggesting that lower Hb levels in blacks and whites may be a consequence of environmental factors related to disease rather than racial causes.19 Results from a literature review found that hematological means in blacks differ from those in whites, regardless of socioeconomic class.19 More specific investigations of both the genetic and environmental determinants of iron utilization in blacks are needed. Until studies show that the lower Hb levels in blacks represent a normal physiological variation, race-specific Hb standards are not recommended.
Definitions of iron deficiency (ID) were less consistent across studies. ID is a reduction in body iron to the extent that cellular stores of iron are fully exhausted, and it can occur with or without anemia.20 There are several laboratory methods that can be used to measure iron in the body, each with its own strengths and limitations, including mean corpuscular volume (MCV), erythrocyte zinc protoporphyrin (ZnPP), transferrin saturation, serum ferritin (SF), and serum transferrin receptor (TfR).20 The majority of studies in this review used SF to define ID; however, several studies used a combination of iron measures (Table 3). Other micronutrients that can cause anemia when levels are inadequate, such as folate, vitamin B12, and vitamin A, were infrequently reported in studies, but the definitions used are reported where available (Table 3).
Results by country
Australia. Seven studies reported on anemia among Australia's indigenous Aborigines. The validity of the sampling approach and representativeness of the study population were rated as poor in three studies, as moderate in three studies, and as good for a single study (Table 2). Four studies examined modest sample sizes (<500) of children from select communities. Only one study defined the indigenous group specifically as Torres Strait Islander participants21; the remaining studies referred to the indigenous study populations simply as “Aboriginal” (Table 3).
Two studies, which were rated as poor in terms of validity and representativeness of sampling method, reported the prevalence of anemia among Aboriginal children to be 16.4% 21 and 75.0%.22 The study by Heath and Panaretto,21 which found a prevalence of anemia of 16.4% among Aboriginal children found a significantly lower prevalence of anemia among non-Aboriginal children (4.2%, P = 0.02).21 There were no statistically significant differences between Aboriginal and non-Aboriginal children for eosinophilia (a possible indicator of parasitic infections), ID, and IDA.21 The prevalence of ID (SF < 15 µg/L and MCV < 74 fL) was 3.6% among Aboriginal and 0% among non-Aboriginal (P = 0.11) children. The prevalence of IDA (ID and Hb < 115 g/L) was 3.6% among Aboriginal children and 0% among non-Aboriginal children (P = 0.11). The causes of anemia, as indicated in the study report, remain unclear; however, based on a 24-hour food diary, the Aboriginal children reportedly consumed less dairy (P = 0.007), meat (P = 0.013), and vegetables (P = 0.014) compared to the non-Aboriginal children.21 An association between ID and dietary intakes was not reported, but one could speculate that lower meat and vegetable intakes would negatively impact iron levels over time, since meat contains heme iron, and vitamin C from vegetables aids in iron absorption; however, lower intakes of dairy may positively impact iron levels, since calcium is an iron inhibitor.7
The high prevalence of anemia (75%) in the study by Hopkins et al.22 is likely due to the high hookworm rates that were present at the time the study was conducted in 1992. Infections with hookworm were present in 77% of Aboriginals and were found to be significantly associated with anemia (P < 0.001) and ID (P < 0.01), suggesting that hookworm infection was a major contributor to IDA.22 While dietary intakes were not measured in the study, the authors allude to the possibility that inadequate dietary iron intake is also a major cause of anemia, particularly in children and women; subjects in these groups had higher rates of ID than men, and hookworm-negative Aboriginal women over the age of 14 years showed high levels of ID (50%) and IDA (31%).22
Only one study reported on anemia among non-Aboriginal children.21 This study was rated as poor because of the small sample size, lack of reporting of the response rate, and selective sampling frame (i.e., children aged 4–12 years from three schools).21 The prevalence of anemia was significantly higher among Aboriginal children (16.4%) compared to non-Aboriginal children (4.2%, P = 0.02). Two studies, rated as good and moderate in quality, reported the prevalence of anemia among Aboriginal children to be 14%23,24 and 24%25; however, neither of these studies examined the causes of anemia. In a national study on lead exposure, Mackerras et al.26 found that the prevalence of anemia among Australian children between the ages of 1 and 4 years, weighted to 1996 census data, was 2% (95% CI: 1.3–3.1).26 Overall, when comparing the prevalence of anemia among Australian children reported in these studies, it is clear that Aboriginal children fare far worse than their non-Aboriginal counterparts.
Three studies reported on anemia among pregnant women using retrospective data from statewide perinatal databases. In Western Australia, Aboriginal adolescent mothers (age range: 12–18 years) from a single obstetric hospital had a significantly higher prevalence of anemia, defined as Hb < 100 g/L (23%) compared to non-Aboriginal adolescent mothers (8%, P < 0.001).27 In South Australia, the prevalence of anemia (not defined) among pregnant women between 15 and 19 years of age was 25.2% among Aboriginals and 9.9% among non-Aboriginals.28 Adolescent Aboriginal mothers were more than twice as likely to be anemic compared to their non-Aboriginal counterparts (relative risk [RR]: 2.54; 95% CI: 2.11–3.04).28 In the state of Queensland, the prevalence of anemia (Hb cut-off not reported) among pregnant women of all ages was 3.3% among Aboriginals and 1.1% among non-Aboriginals.29 Differences in anemia prevalence may be related to the definition of anemia. Since pregnancy is characterized by increased blood volume, a normal physiological change that causes a reduction in the blood concentration of Hb, a lower Hb cutoff is required for defining anemia in pregnant women.7 Westenberg et al.28 and Wills and Coory29 did not report the Hb level used to define anemia (Table 3).28,29 The lower prevalence of anemia among pregnant women in Queensland compared to those in South Australia and Western Australia may be a result of particular conditions in the geographic area or of the age of the women examined (all ages versus adolescent females). Indigenous women were found to have higher teenage pregnancy rates, higher teenage birth rates, and higher smoking rates compared to non-indigenous women.27–29 In all three settings, Aboriginal women had higher rates of anemia compared to non-Aboriginal women. Overall, these results suggest anemia is more prevalent among Aboriginals compared to non-Aboriginal Australians and, based on the WHO criteria, is a moderate public health problem.15
Brazil. Among the studies reviewed, two were conducted in Brazil and one was among indigenous people living in the Amazon in Brazil and Venezuela.30 The study by Morais et al.31 sampled Terena Indian infants aged 6–120 months from two villages and was given a moderate quality rating. By age group, the prevalence of anemia was 86.1% among infants aged 6–24 months, 50.8% among infants aged 24–60 months, and 40.7% for children aged 6–120 months.31 The study by Orellana et al.32 was rated as good and sampled all infants between the ages of 6 and 119 months in 9 of the 11 villages inhabited by Surui Indians. The prevalence of anemia was 62.3% among Terena Indian infants and 80.6% among Surui Indian infants (Table 3).31,32
There was no data on the etiology of anemia; however, based on previous data from Brazil, Morais et al.31 suggested anemia is mostly due to ID and blood loss from intestinal parasites. In the study by Orellana et al.,32 one of every four children was undernourished and, according to previous data, the infant mortality rate for Surui Indians (70/1,000 in 2004) was more than twice as high as the average for the general Brazilian population. Both authors referred to poor living conditions, including inadequate water and sewage treatment systems, as likely causes of anemia. In terms of infectious causes of anemia, malaria was apparently interrupted two decades ago and a recent parasitological survey found a low prevalence of hookworm infection (<5%).32
The study conducted in the Brazilian and Venezuelan regions of the Amazon was a cross-sectional survey of Yanomami people of all ages living in 11 communities that were randomly selected from census data.30 The study found that 70.5% of the Yanomami people living in the Ocamo area of the Amazon in Brazil and Venezuela were anemic.30 Unfortunately, the prevalence of anemia was not reported separately by age group, thus limiting our understanding of anemia in high-risk age groups such as infants and women in this region. However, as in the two other studies performed in Brazil, the high prevalence of anemia suggests the condition is a severe public health problem among various indigenous peoples in the country.15
Canada. Among the four studies (seven articles) conducted in Canada that met the inclusion criteria, none included a non-indigenous comparison group (Table 2). One study of Nunavik pregnant women found that 39% were mildly anemic (Hb < 120 g/L) and 22% were moderately anemic (Hb < 115 g/L).33 Among the Nunavik women sampled, 27% had positive or equivocal Helicobacter serology results. Further information on possible nutritional causes of anemia were not available due to the retrospective nature of the study design.33
Four studies examined infants of Cree, Inuit, or First Nations descent between the ages of 3 and 60 months.33–38 Between 1995 and 1998, Willows et al.39 examined 354 Cree infants at their 9-month well-baby clinic visit and found that 7.9% (95% CI: 5.3–11.2) had anemia (Hb < 110 g/L), 31.1% (95% CI: 26.2–36.1) had moderate anemia (Hb < 105 g/L), and 17.2% (95% CI: 13.4–21.5) had severe anemia (Hb < 100 g/L). Between 1998 and 2000, Willows and Gray-Donald reported on 274 Cree infants at their 9-month well-baby clinic visit and found that 25.6% were anemic (Hb < 110 g/L).36–38 Between 2001 and 2003, Christofides et al. found 36% of Inuit and First Nation infants (4–18 months old) to be anemic.34,35 A study by Hodgins et al.33 in 1989–1992 found that 58% of Inuit infants were anemic and 39% (Hb < 120 g/L) of Inuit women were anemic.
In terms of the etiology of anemia, Christofides et al. and Willows et al. discuss infant feeding practices and the need to address socioeconomic conditions that prevent healthy feeding practices from being adopted, such as the continued use of cow's milk/evaporated milk, which is low in iron and nutritionally replete instead of formula, because cow's milk is less expensive and more readily available.34–38 In their study, Christofides et al.34 found anemia to be significantly associated with Helicobacter pylori infection (OR: 3.10, 95% CI: 1.01–9.51), consumption of cow's/evaporated milk (OR: 2.84, 95% CI: 1.24–6.50), and prolonged breastfeeding (OR: 2.47, 95% CI: 1.04–5.85); formula intake was significantly associated with risk of ID (sTfR > 8.5 mg/L) (OR: 0.35, 95% CI: 0.15–0.84). The high prevalence of H. pylori suggests a need to improve water quality and sanitation in the indigenous communities studied.34,35 In the studies by Willows and Gray-Donald,36–38 the authors found that concentrations of microcytic erythrocytes were higher among infants who were breastfed (OR: 10.7, 95% CI: 3.9–29.0), fed cow's milk (OR: 9.2, 95% CI: 3.2–26.8), and fed mixed milks (OR: 7.3, 95% CI: 2.2–23.9) in comparison with formula-fed infants. The authors also reported that thalassemia minor is not present in Cree infants. Based on the available evidence, the level of anemia among indigenous groups in Canada appears to represent a moderate public health problem.15
Guatemala. A single study of Mayan people in Guatemala was found for the present review.18 The study collected data on 253 women from 17 villages with the aim of examining the association between smoky indoor cooking fires and elevated Hb concentrations, but it did not indicate how representative these 17 villages were of the total Mayan community nor did it report the survey response rate. The study was conducted in 1994 and found that 25% of Mayan women (15–45 years old) were anemic and 31% had depleted iron stores. Since no other studies that reported on anemia in indigenous populations in Guatemala were found, the prevalence of anemia in the Mayan community and in other indigenous populations in Guatemala is essentially unknown. Nevertheless, this study indicates anemia among Mayan women is a health issue that warrants clinical attention.
India. Twelve of the studies reviewed were conducted in India. These studies varied widely in terms of the age and tribal groups investigated. Of the four comparison group studies, only the study by Ghosh and Bharati41 included a significance test, and a statistically significant difference in the rates of anemia was found between tribal and non-tribal groups. The study examined married women between the ages of 15 and 42 years in a periurban area in Kolkata city and found that anemia, of varying degrees, was more prevalent among women belonging to the Munda tribe compared to women belonging to the Poundrakshatriya Hindu caste (P < 0.001).41 The rates of mild (Hb 100–119 g/L), moderate (Hb 70–99 g/L), and severe (Hb < 70 g/L) anemia were 37.1%, 55.2%, and 7.6%, respectively, among Munda tribe women compared to 48.6%, 9.7%, and 2.9% of 9.7%, respectively, among women belonging to the Poundrakshatriya Hindu caste (Table 3).41
A population-based study conducted in the state of West Bengal by the National Nutrition Monitoring Bureau found a significantly higher prevalence of anemia (Hb < 110 g/L) among Scheduled Tribe children between the ages of 1 and 5 years compared to other children in the community.42 This study in West Bengal among rural children highlighted the high prevalence of anemia among all children due to diets with inadequate micronutrient content, most notably iron, and poor hygienic conditions – the majority of children practiced open defecation, as sanitary facilities were absent in 81% of households.42 While the authors did not have data on hookworm infection, they reported the importance of periodic deworming among children as a preventive measure for anemia and IDA.42
The study by Kotecha et al.43 examined 895 tribal and 1,965 non-tribal girls aged 12–19 years from schools in the Vadodara district of Gujarat. While the authors did not report a significance test, the prevalence of anemia was relatively similar between tribal (73.7%), rural (74.5%), and urban (75.8%) areas.43 After 17 months of educational intervention about iron and folic acid supplementation, the overall rates of anemia decreased by 21.5 % (from 74.7% to 53.2%, P < 0.05).43
In Nagpur district in Maharashtra, Menon et al.44 examined non-pregnant women between the ages of 18 and 30 years and found that anemia rates in tribal versus non-tribal women were 72% versus 53%, respectively (P = 0.07). In a district in central India, Singh et al.45 studied 456 tribal women between the ages of 18 and 40 years and found that anemia was commonly present in most (80%) of the women. Approximately 21% of the women in this study were found to be infected with malaria.45 While the authors did not report on any nutritional or genetic causes of anemia, they reported the high probability that dietary inadequacy played an important role. More than 60% of pregnant women without malaria were also anemic. Among women with malaria, anemia was more frequent in multigravidae versus primigravidae women (69.6% versus 54%, respectively); thus, highly prevalent anemia of nutritional origin appears to be further aggravated by pregnancy.45
Six non-comparison studies were conducted in different states and among diverse tribal peoples of varying ages, making comparisons among studies very difficult, if not impossible.46–52 The prevalence of anemia (Hb < 110 g/L) ranged from 16.2% among male Bhil and Pawar adolescents (12–18 years old) in Jalbalpur state to 86.7% among Gond children of all ages in Madhya Pradesh (Table 3).
Studies reported a high proportion of parasitic infections related to unhygienic living conditions as well as poor nutrition and a high prevalence of low-birth-weight infants.41,46,47 While not measured in any of the studies described, authors also discussed previous studies in Indian populations in which thalassemia and hemoglobinopathies were found.47 Levels of anemia across the heterogeneous group of studies suggest that anemia is a severe public health problem for women and children in both tribal and non-tribal groups in India.15
Kenya. A single study from Kenya was included, which was conducted in Kismu. This study sampled 3,645 healthy pregnant women of all ages from a single hospital to assess risk factors for anemia in late pregnancy.53 Results were reported by gravidity. Among women in primi- and secundi-gravidae, those from the Luo tribe had a higher prevalence of anemia (Hb < 110 g/L) relative to non-tribal women (81.6% versus 70.6%, respectively; RR: 1.16; 95% CI: 1.10–1.22) and a higher prevalence of severe anemia (Hb < 70 g/L) (7.5% versus 5.1%, respectively; RR: 1.47; 95% CI: 1.02–2.12) (Table 2).53 Among women in gravidae three or more, those from the Luo tribe had a higher prevalence of anemia compared to non-tribal women (76.5% versus 69.5%, respectively; RR: 1.10; 95% CI: 1.02–1.19) and a higher, but not significantly different, prevalence of severe anemia (7.1% versus 4.5%, respectively; RR: 1.57; 95% CI: 0.92–2.68).
The study did not measure iron status or other micronutrient causes of anemia; however, a high seroprevalence of malaria and HIV was found among all women (tribal and non-tribal). The level of anemia reported in this single study suggests that among both tribal and non-tribal pregnant women in Kenya anemia is a severe public health issue.15
Malaysia. Three studies on anemia among indigenous populations in Malaysia were identified. Two studies were conducted among the indigenous Orang Asli population.54,55 One study examined 368 Orang Asli children aged 2–15 years living in eight villages in the state of Selangor and found that 41.5% were anemic (Hb < 120 g/L).55 Similar findings were reported in a single school-based study in the state of Pahang that evaluated 241 Orang Asli children; in this study, 48.5% (95% CI: 42.3–54.8) of Orang Asli children aged 7–12 years were anemic (Hb < 120 g/L) (Table 3).54 Iron deficiency accounted for 61% of anemia cases in the Selangor study and 70.1% of cases in the Pahang study.54,55 The Selangor study examined stool samples from a subsample of children (n = 281) and found the prevalence rates for hookworm, trichuriasis, ascariasis, and giardiasis were 19%, 26%, 3%, and 24.9%, respectively.55 In the Pahang study, the prevalence rates for hookworm and ascariasis were 13.4% and 22.3%, respectively.54
In a study of indigenous people by Sagin et al.56 seven villages were selected in five remote communities in Sarawak. Among indigenous people between the ages of 5 and 85 years, the researchers found that 29.2% of males were anemic and 17.2% of females were anemic.56 Anemia was almost twice as common in males (29.2%) than females (17.2%), except for adolescent and reproductive females (31.6%). The authors speculated that the higher incidence of anemia in men aged 40 years and older may be a result of nutritional deficiency or alcoholism.7
According to Sagin et al.,56 the area of the Amazon Basin they examined has undergone large-scale development projects and the diet of the indigenous peoples has changed from traditional nomadic diets to imported and processed foods. The two studies described here indicate anemia is a moderate public health problem in the Sarawak population and a severe public health problem among Orang Asli children.15
Mexico. Mexico produced the highest quality of evidence regarding anemia in indigenous populations. Five articles reported data for women and children from the National Nutrition Survey (NNS) in 1999.57–60 The prevalence of anemia among indigenous and non-indigenous groups in various age groups were as follows: 35.8% versus 26.1% for children younger than 5 years, 24% versus 19% for children aged 5–11 years, and 24.8% versus 20.4% for adult mothers.57–60 Data comparing rates of anemia among children from the Mexican National Health and Nutrition Survey (2006) and the Mexican National Nutrition Survey (1999) indicate the prevalence of anemia has decreased by 1.8 percentage points per year among indigenous toddlers.61 Compared to the national data, lower estimates of anemia were reported in smaller studies among Tarahumara (13%)62 and Yaqui (0.7%)63 indigenous children in Mexico. The lower prevalence of anemia among Tarahumara children compared to national data is postulated to be a result of selection bias (boarding school) and a feeding intervention that had been implemented in the school.64 A study among Tarahumara women in Northern Mexico found that 12.1% of non-pregnant (n = 446) and 17.1% of pregnant (n = 35) women (age range: 12–49 years) were anemic.64 The low rate of anemia among the Yaqui people is likely due to adequate amounts of iron in the Yaqui diet.63 The Yaqui Valley is located in one of the most important agricultural regions in Mexico.63 According to the study's authors, the amount of protein in the diet of Yaqui Indians is adequate, with sufficient amounts of vegetable protein and smaller quantities of animal proteins derived from eggs, dairy products, and occasional fresh or processed meats.63
Among studies that reported on the etiology of anemia, causes included ID and poor socioeconomic conditions.60,64 The median intake of dietary iron for those younger than 5 years of age corresponded to 50% of the recommended daily allowance and reached 80.8% in subjects aged 9–10 years. Iron sources were also found to contain high amounts of phytic acid (>500 mg/day) and tannins.60 Another cause of anemia discussed by Shamah-Levy et al.59 is poverty. The authors state it is well known that indigenous populations are the poorest in Mexico and have the least access to social support services. Based on nationally representative data from the nutrition survey, anemia in indigenous women and children in Mexico is a moderate public health problem.15
New Zealand. Results from a study in Auckland, New Zealand conducted among adolescents in grades 5–7 (ages not specified) in eight schools found a higher prevalence of anemia (Hb < 120 g/L) among female Maori versus non-indigenous students (11% versus 4%).65 The risk ratio of anemia was 2.92 (95% CI: 1.15–7.43) in Maori versus non-indigenous female students (Table 3).65 The prevalence of anemia in this single study suggests anemia may be a mild public health problem among Maori females in this student group; however, the small and selective sample from this single study in a single urban city prevents any conclusions from being made about the level of anemia among indigenous populations in New Zealand in general. Furthermore, the study did not provide information on the etiology of anemia and the authors requested that further research be conducted to examine possible risk factors.
New Zealand conducts population monitoring of dietary intakes and biochemical indices. Published data in the peer-reviewed literature on 15–49-year-old women (n = 1751) from the National Nutrition Survey in 1997 (NNS97) provide estimates of ID and IDA among Maori and non-indigenous New Zealanders.66 Nationally representative population estimates among women for ID (defined as SF < 12 µg/L) were reported as 4.8% (95% CI: 1.9–7.6) among Maori and 4% (95% CI: 2.4–5.6) among non-indigenous New Zealanders.66 IDA defined as Hb < 120 g/L and SF < 12 µg/L was 7.3% (95% CI: 3.2–11.4) among the Maori and 2.5% (95% CI: 1.2–3.9) among non-indigenous New Zealanders.66 While the findings for women from the NNS97 found marginal and generally non-significant differences in the prevalence of IDA or ID across age and ethnic groups, rates were higher among the Maori compared to non-indigenous groups.66 In their commentary, the authors expressed surprise at the lack of significance in these findings, given the higher prevalence rates of IDA and ID reported among Maori students compared with their Caucasian counterparts in the Schaaf et al. study.65 The authors speculated that marked ethnic group differences may only occur in childhood and adolescence.66 The number of adolescents in ethnic groups was limited in the NNS97 data and therefore could not be analyzed separately.66 Another possibility is differential response rate bias for the response to blood collection in the NNS97 (e.g., 73% among non-indigenous New Zealanders compared to 61% among Maori).66 Unfortunately, as the study did not report data on the prevalence of anemia it did not meet eligibility criteria for this review.66
Sri Lanka. A single study in Kelaniya, Sri Lanka compared Veddah (tribal) children to Sinhalese (non-tribal) children between the ages of 6 and 15 years and found anemia (Hb < 115 g/L) was present in 67% of Veddah children compared to 36% of Sinhalese children (P < 0.05) (Table 3).67 Both wasting and anemia were higher among indigenous children. Causes of anemia were reported to be inadequate diet, undernutrition, and high rates of intestinal infections as a result of contaminated drinking water. While there was only one study on anemia among indigenous people in Sri Lanka, its results indicate anemia is a severe public health problem for Veddha children in this country.
Tanzania. One study in northern Tanzania collected data on women aged 14–49 years from 12 antenatal clinics in a single Lutheran hospital.17 The women represented the following tribal groups: Iraqw, Datoga, and others. The overall prevalence of anemia was 22.7%. Among the anemic women, 31.5% had malaria compared to 17.5% of non-anemic women (P < 0.0001). This single study indicates anemia is common in this particular high-altitude, rural region of northern Tanzania, albeit less common than the authors expected, based on previous studies in most other parts of the country.17 The authors cite previous studies of pregnant women in the general population in Tanzania among whom anemia prevalence ranged from 41% to 95%.17 A lower prevalence of diseases such as intestinal worms and sickle cell disease were cited as possible reasons for the lower prevalence of anemia among women in the rural area studied compared to previous estimates from other areas in Tanzania. The authors indicate further studies on the micronutrient status of the women are needed in order to identify more specific etiological factors.17
United States of America. One study from the United States that examined anemia among an indigenous population met the inclusion criteria. Two articles by Gessner68,69 reported results from a retrospective, 1999–2006 cohort based on data from the US Supplemental Nutrition Program for Women and Infants (WIC). The prevalence of anemia was higher among Native Alaskan infants compared to non-Native Alaskan infants at 10–23 months of age (35% versus 21%, respectively) and at 24–59 months of age (22% versus 12%, respectively).68 The relative risk of anemia among Alaskan Natives versus non-Native Alaskans was 1.7 (95% CI: 1.6–1.7) for infants 10–23 months old, and 1.9 (95% CI: 1.8–2.0) for infants 24–59 months old.68 Among pregnant or postpartum women, Alaskan Natives had higher rates of anemia (25%) and severe anemia (3.5%) compared to non-Native women (15% and 1.3%, respectively).69 Analyses adjusted for Hb levels found the following significant factors: age, Alaskan Native status, rural residence, number of previous pregnancies, maternal prenatal tobacco use, and female gender.69 The magnitude of anemia among Alaskan Native women and children, based on the studies by Gessner, suggests anemia is a moderate public health problem in this segment of the US population.68,69
Venezuela. There have been few hematological studies on indigenous people in Venezuela, but two studies were identified that reported on anemia since 1996. One study, conducted in the Amazon, reported on anemia among 182 Piaroa people of all ages using data from a single medical facility.70 The study found that 89.6% of Piaroa people were anemic, and 35.6% of them were iron deficient. A second study collected data from two groups of Bari Indians; 179 subjects were from the Campo Rosario community and 287 were from the Salmadoyi community.71 The two communities differ greatly in their location and access to food. As described by the study authors, the Bari Indians from the Campo Rosario community live in an arid area with impoverished agriculture and maintain a diet of pasta or rice cooked with onions, sweet peppers, and yuca (a starchy vegetable).71 Vegetables, fruit, and meat are scarce, aside from the occasional smoked monkey. In contrast, the Salmadoyi community is in a fertile valley with access to vegetables, fruit, and domestic animals.71 In the Campo Rosario community, anemia was 53.6%, ID was 20.3%, folate deficiency was 91%, and vitamin B12 deficiency was 64.4% (Table 3). Micronutrient deficiencies in the Campo Rosario community are likely the result of inadequate diet and parasitic infections from food and water contamination.71 The more nutritious Salmadoyi diet is reflected in lower levels of observed micronutrient deficiencies, i.e., anemia was 30.6%, ID was 5%, folate deficiency was 5.1%, and vitamin B12 deficiency was 0% (Table 3). Based on evidence from these two studies, anemia is a severe public health problem among secluded indigenous populations in Venezuela that have limited access to a diverse diet and to governmental health programs (Table 3).