Preplanned Studies: Variations in the Prevalence of Anemia of Varying Severity Among Urban Non-Pregnant Women — China, 2021

Anemia represents a significant global public health concern, being identified as the third most prevalent cause of disability worldwide according to the Global Burden of Disease Study (1). Women are disproportionately affected by anemia compared to men. In China, the emphasis of governmental and research efforts on anemia has predominantly centered on pregnant women and those of reproductive age, with insufficient attention given to anemia in other groups, such as elderly women. Previous studies have primarily focused on anemia prevalence among Chinese women, with a lack of comprehensive data for non-pregnant women across all age groups (2–4). This study aimed to assess the prevalence of anemia by severity among non-pregnant women in urban areas of China at both national and provincial levels, while also evaluating the socioeconomic disparities in anemia prevalence. The research included a total of 6,034,533 non-pregnant women aged 18 years and above from all 31 provincial-level administrative divisions (PLADs) in China’s urban regions between January 1, 2021, and December 31, 2021. Findings revealed that 14.8% of non-pregnant women aged 18 years and above in urban China experienced anemia, with 5.7% classified as having moderate to severe anemia. Anemia prevalence exhibited significant variations correlated with factors such as age, body mass index (BMI), geographic location, and economic status. It is imperative for comprehensive anemia intervention strategies to specifically target non-pregnant women aged 30–49 years and those aged 70 years and above, adapting to the varying levels of socioeconomic development and geographical disparities.

The data for this study were obtained from the Meinian Healthcare Group system, which, as China’s largest health exam chain, offers extensive services with facilities in 231 prefecture-level cities across 31 PLADs (5). The population investigated was comprised primarily of employees (70%) and non-working urban residents. Standardized procedures were employed to collect socio-demographic data, physical measurements, and biochemical indices from venous blood samples. Within the period from January 1, 2021, to December 31, 2021, a total of 6,034,533 non-pregnant women aged 18 years and above were eligible for and included in the analysis. The World Health Organization (WHO) defines anemia in non-pregnant women aged 15 years and over as a hemoglobin concentration below 120.0 g/L. Levels ranging from 110.0 to 119.0 g/L are classified as mild anemia, 80.0–109.0 g/L as moderate, and below 80.0 g/L as severe (6). Hemoglobin levels were adjusted for the mean altitude of the prefecture-level cities. Socioeconomic factors were represented by the city-level Engel coefficient and gross domestic product (GDP), which were categorized into quartiles and merged with individual participant data. For analytical purposes, China’s geographic regions were segmented into six areas: the northern, eastern, central, southwestern, northwestern, and northeastern.

Using the sample structure as a reference and adjusting for population distribution by PLAD and age, we calculated standardized prevalence rates and their 95% confidence intervals (CIs). We employed the χ² test with the Rao-Scott correction to assess differences across groups. To explore the relationship between anemia and various socioeconomic factors, we adjusted for age, BMI, history of cesarean delivery, GDP, systolic blood pressure, total cholesterol, hyperuricemia, glomerular filtration rate, and geographic region using multivariable logistic regression that accounted for clustering effects. SAS software (version 9.4, SAS Institute Inc., Cary, NC, USA) was used for all statistical analyses. We conducted two-sided statistical tests, with a P-value of less than 0.05 considered to indicate statistical significance. The Peking University Institutional Review Board (IRB-0000152-19077) provided ethical approval for this study.

The average age of eligible women was 48.4 years [standard deviation (SD)=14.5], with 2,834,987 aged 50 years and older. Among them, 43.1% were overweight or obese, 3.9% had a history of cesarean delivery, and 59.8% lived in eastern or central China.

In 2021, an estimated 14.8% (95% CI: 13.9%, 15.5%) of non-pregnant women were found to have anemia, with 5.7% (95% CI: 5.4%，6.0%) experiencing moderate to severe anemia (Table 1). The prevalence of anemia varied based on factors such as age and region. Urban non-pregnant women aged 40–49 years showed the highest prevalence of moderate to severe anemia at 10.6% (95% CI: 10.1%, 11.1%), followed by those who had a prior cesarean delivery (8.4%, 95% CI: 7.7%, 9.1%), were underweight (6.6%, 95% CI: 6.1%, 7.0%), and resided in the northwest region (6.3%, 95% CI: 5.5%, 7.1%).

The prevalence of anemia varied among PLADs, ranging from 5.6% to 38.0% (Figure 1), with the highest rates observed in Xizang, Guangxi, and Hubei PLADs. Moderate to severe anemia prevalence ranged from 3.5% to 15.6%. Anemia prevalence by PLAD exhibited distinct patterns across various age groups of women.

Figure 1. 

Regional disparities in the prevalence of anemia among non-pregnant women in urban China, standardized by age, 2021. (A) Anemia among all women; (B) Anemia among women aged 18–49; (C) Anemia among women aged 50 and over.

Multivariable logistic regression analysis revealed that individuals aged 30–49 and those 70 years and older, along with those who are underweight, were significantly more likely to have anemia when compared to their respective reference groups. Additionally, residents in the central, eastern, northern, and northwestern regions of China displayed a higher prevalence of anemia (Table 2). Women residing in regions with the lowest GDP had an increased likelihood of moderate to severe anemia, with odds ratios (OR) of 1.18 (95% CI: 1.04, 1.34) for both the age groups of 18–49 years and those above 49 years. In separate analyses, urban non-pregnant women aged 18–49 living in the lowest GDP areas (OR=1.16, 95% CI: 1.03, 1.31), with a history of cesarean delivery (OR=1.06, 95% CI: 1.01, 1.12), and those who are obese (OR=1.03, 95% CI: 1.01, 1.06) were found to have a greater risk of moderate to severe anemia. For non-pregnant women aged 50 years and above, a lower Engel coefficient (OR=1.24, 95% CI: 1.05, 1.47) and being underweight (OR=1.71, 95% CI: 1.63, 1.79) were associated with an increased risk of anemia.