Assessment of Anemia Prevalence Among Non-Pregnant Women in Urban Areas of Shanghai and Tokyo: A Retrospective Observational Study

Introduction: Anemia, one of the most common and widespread disorders in the world, is a public health problem, and among various causes, iron deficiency is the most common cause of anemia, affecting more than 2.2 billion people worldwide. In developing countries, insufficient dietary intake is a main cause whereas eating habits like vegetarian diet or avoidance of red meat is associated with anemia in developed countries. Shanghai has been sharing many characteristics with Tokyo not only in rapid economic growth and westernization but also in more volition on personal life and late marriage in women of child-bearing age. Here in this study, with the large-scale database in both areas, the prevalence of anemia was elucidated among non-pregnant women age in urban areas of representative Asian countries undergoing routine annual health checkups.

Methods: All participants in this retrospective observational study were limited to women aged between 20 and 44. A total of 2,006 health checkup data (from May to September 2016) from residents of Xinqiao, Sheshan and Maogang towns in Songjiang District by stratified cluster sampling were collected. These three towns are located in the southwestern part of Shanghai and their population is approximately 230,000 in total. A total 877 health checkup data (from February to July 2017) from 1,087 employees in the dispensing pharmacies in Tokyo area were collected. Anemia was defined as a hemoglobin (Hb) concentration lower than 12.0 g/dL, which was further categorized as mild (10.0<Hb≤12.0), moderate (7.0<Hb≤10.0) and severe (<7.0). Microcytic anemia was defined as Hb < 12 and a mean corpuscular volume (MCV) < 80 fL. In-group comparisons regarding anemia prevalence according to age and body mass index (BMI) were conducted.

Results: Medians of age, BMI, Hb and MCV in Shanghai area (SA) group were 36 y.o. (range; 20-44), 21.7 (14.7-41.5), 13.1 (6.4-17.9) and 91.6 (59.0-107.2), while these in Tokyo area (TA) group were 36 y.o. (20-44), 20.5 (13.3-42.8), 13.0 (8.7-16.0) and 91.0 (61.0-106.0). Anemia was seen in 14.8% (n=297) of participants in SA and 11.4% (100) of participants in TA, among which prevalences of mild and moderate anemia were 12.2% (SA: 244) / 10.0% (TA: 88) and 2.6% (SA: 53) / 1.4% (TA: 12), respectively. No severe anemia was detected. Microcytic anemia was found in 5.7% (115) of SA and 3.4% (30) of TA. In-group comparison according to age (persons aged 20-24, 25-29, 30-34, 35-39, 40-44) showed a gradual increase of anemia prevalence in SA, the highest prevalence of 20.8% in persons aged 40-44. By contrast, in TA group, persons aged 30-34 had the highest prevalence of 14.7%. Another in-group comparison by BMI (<18.5, 18.5≤BMI<25.0, 25.0≤BMI<30.0, 30.0≤) revealed an inverse correlation to anemia prevalence, the highest of 18.2% in SA group, while in TA group persons with BMI ranging 18.5-25.0 had the highest of 10.8%.

Discussion and Conclusion: Using the large-scale database of health checkup program, our analysis of CBC data revealed that high prevalence of anemia was associated with older age and lower BMI in SA group but that the prevalence of anemia in TA group had no correlation with age and BMI. First of all, the difference of recruitment for health checkup between the two areas was a possible cause. People who have health checkup might be more interested in healthy lifestyle, possibly generating selection bias in our study. And multiple factors including calorie intake, type of diet, iron supplementation and so on would affect the difference. Besides them, it is of note that beta thalassemia is highly prevalent in south China, which might contribute to the difference. Although the prevalences of anemia in two areas were lower than the global prevalence of about 25%, there still exists a sizable anemic population even in urban areas of developed countries, suggesting the importance of considering regional difference in etiology of anemia. Still needed further study with larger cohorts with detailed parameters, our data could provide an important information about anemia prevalence in two major Asian metropolises, constructing a basis of anti-anemia countermeasures for women of child-bearing age. Our findings call for well-designed public health policies with more individualized approach reflecting on eating and social habits in such urban areas.