Anemia is a common condition at all ages, but this is especially true among the older population since the prevalence of anemia rises with advancing age (Baducci, 2003; Nissenson et al., 2003). According to the results of some epidemiologic studies, the prevalence of anemia among adults increases sharply after the age of 60 (Ania et al., 1994, 1997; Smith, 2000). Due to the rising tendency of the aging population in a modern society, the prevalence of anemia is also expected to rise in the future. Anemia represents a sign of serious diseases. Thus, if not treated properly, anemia can cause severe complications, especially among the older population. In a large epidemiologic study with the subjects over 65 years who were hospitalized for acute myocardial infarction, lower hematocrit levels were reported to be associated with higher mortality rates (Izaks et al., 1999; Kikuchi et al., 2001). Undiagnosed and untreated anemia is also associated with a decreased quality of life (Ma et al., 1999; Moreno et al., 2000), and therefore, early detection of anemia among the older population is an important topic.

In order to establish a proper diagnostic and treatment strategy, the assessment of the prevalence and clinical characteristics of the elderly population in rural area is important since many studies have been conducted in urban areas rather than in rural areas. Number of studies have reported age-specific hematologic values of older population (Ania et al., 1994, 1997; Celestin-Roux et al., 1987; Choi et al.,. 2004; Hake et al., 1983; Izaks et al., 1999; Salive et al., 1992; Smith, 2000; Timiras & Brownstein, 1987; Zauber & Zauber, 1987), but the interpretation of the results is complicated due to possible limitations of study populations and the availability of data on related factors. Among the number of studies reported so far on the prevalence of anemia in the older population, only a limited number of studies have been conducted on community-base setting (Izaks et al., 1999; Salive et al., 1992). Furthermore, there are even less studies on the prevalence and clinical characteristics of anemia in East Asian countries and the rural area of these countries.

The objectives of this study, therefore, were focused on assessing the prevalence and clinical characteristics of anemia and on defining the risk factors for anemia among older rural Koreans living in Asan.

Anemia among the older population used to be considered as a part of the normal physiological process of aging (Lipschitz & Mitchell, 1981). However, the current trends more likely consider anemia among the older population as a type of pathologic condition caused by underlying diseases (Hake et al., 1983; Salive et al., 1992; Stander 1989). Thus, anemia is no longer viewed as a natural physiological change of an accompaniment of aging. In this study, we assessed the prevalence of anemia in a community-based group in the rural area that was fully ambulatory and capable of normal, active daily life. Our results showed that the prevalence of anemia among rural older subjects was 12.5% (10.8% in men and 13.6% in women). These are lower than the results of other studies (Ania et al., 1994; Choi et al., 2004; Izaks et al., 1999; Salive et al., 1992; Timiras & Brownstein, 1987), but differences in the age of participants and the study settings make direct comparisons impossible. When the prevalence was compared with urban Korean elderly (Choi et al., 2004) in men and women separately, the prevalence of anemia in rural men (10.8%) was higher than the urban men (9.9%) while rural women showed the lower prevalence than urban women (13.6% vs. 14.7%). As shown in the previous report on the nutritional status of the rural population (Kim et al., 2007), rural men might be more subject to poor nutrition quality than both rural women and urban men. The low socioeconomic status of rural men may have caused higher anemia prevalence than urban men. Consequently, more efforts to improve nutritional status of rural men are needed.

The prevalence of anemia is significantly higher in the older group in this study as other epidemiologic studies have reported (Ania et al., 1994, 1997; Choi et al., 2004; Salive et al., 1992; Smith, 2000). As shown in Table 2, significant differences were found between the anemia prevalence in those aged 60-69 y and those aged 80 y or older. In addition to the prevalence study, we investigated the characteristics of anemia and risk factors in the older population by comparing variables for the normal and anemic groups. Anemic subjects showed lower anthropometric status, total protein and albumin levels, lipid profiles (cholesterol and triglyceride) and all iron status indexes except TIBC. Also the significantly higher age in the anemic subject was reported. When the characteristics of anemia were analyzed by MCV values, normocytic anemia was the most common type of anemia. However, the rate of macrocytic anemia resulting from vitamin B₁₂ and/or folate deficiency among this population was higher (8.9%) than the urban older population (3.0%, Choi et al., 2004). Since anemia is commonly caused by various pathological conditions such as chronic disease, iron deficiency, vitamin B₁₂ and/or folate deficiency, the specific characterization of anemia in this population needs to be conducted with the evaluation of vitamin B₁₂ and folate status.

Low serum albumin and high creatinine levels were analyzed to be the risk factors of anemia among the rural older population. The low albumin level might be due to either insufficient nutrient intakes or chronic illness. The high creatinine level is associated with anemia due to a reduction in the circulating erythropoietin level (Carmel, 2001). Therefore, we may speculate that the anemia of this population could be due to insufficient nutrient intakes and chronic diseases; however, because of the lack of information on nutrient intake and chronic disease status, further investigation is needed. Considering the rural older population is not easily accessible to better medical services than the urban population, the underlying condition of anemic subjects could be due to causes other than iron deficiency. Approximately 85% of anemia cases have been defined (Carmel, 2001; Smith, 2000) and reported prevalence of vitamin B₁₂ deficiency among older adults aged over 60 y was about 10-15 % (Baik & Russell, 1999). Therefore, more specific tests such as analyses of vitamin B₁₂ and folate status and tests for the underlying chronic disease conditions would be helpful to reveal additional causes of anemia in this population.

In this study, we found 12.5% overall prevalence of anemia among older adults living in rural Asan. This rate is lower than the previously reported anemia prevalence among the urban older Koreans. However, anemia in men of this study was higher than the urban older men. Morphologically, normocytic anemia was the most common type in this population while more macrocytic anemia was reported than the urban population. Significant risk factors identified were low serum albumin and high creatinine levels. The cause of anemia in this population might be mostly due to chronic disease and insufficient micronutrient intakes such as iron, vitamin B₁₂ and/or folate. For the future work, nutritional status of micronutrients must be evaluated either by dietary and biochemical analyses and strategies to improve the nutritional and health status of the rural older population must be developed.