Serum Albumin Levels and Economic Status in Japanese Older Adults.
BACKGROUND
Low serum albumin levels are associated with aging and medical conditions such as cancer, liver dysfunction, inflammation, and malnutrition and might be an independent predictor of long-term mortality in healthy older populations. We tested the hypothesis that economic status is associated with serum albumin levels and explained by nutritional and health status in Japanese older adults.


METHODS
We performed a cross-sectional analysis using data from the Japan Gerontological Evaluation study (JAGES). The study participants were 6528 functionally independent residents (3189 men and 3339 women) aged ≥65 years living in four municipalities in Aichi prefecture. We used household income as an indicator of economic status. Multiple linear regression was used to compare serum albumin levels in relation to household income, which was classified as low, middle, and high. Additionally, mediation by nutritional and health-related factors was analyzed in multivariable models.


RESULTS
With the middle-income group as reference, participants with low incomes had a significantly lower serum albumin level, even after adjustment for sex, age, residential area, education, marital status, and household structure. The estimated mean difference was -0.17 g/L (95% confidence interval, -0.33 to -0.01 g/L). The relation between serum albumin level and low income became statistically insignificant when "body mass index", "consumption of meat or fish", "self-rated health", "presence of medical conditions", "hyperlipidemia", or "respiratory disease "was included in the model.


CONCLUSIONS
Serum albumin levels were lower in Japanese older adults with low economic status. The decrease in albumin levels appears to be mediated by nutrition and health-related factors with low household incomes. Future studies are needed to reveal the existence of other pathways.
Division of Health and Nutrition, University of Niigata Prefecture, Niigata, Japan.
Asami
A
Ota
Department of Health and Social Behavior/Department of Health Education and Health Sociology, School of Public Health, The University of Tokyo, Tokyo, Japan.
Naoki
N
Kondo
Division of Health and Nutrition, University of Niigata Prefecture, Niigata, Japan.
Nobuko
N
Murayama
Division of Health and Nutrition, University of Niigata Prefecture, Niigata, Japan.
Naohito
N
Tanabe
Division of International Health, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan.
Yugo
Y
Shobugawa
Center for Preventive Medical Science, Chiba University, Chiba, Japan.|Center for Well-being and Society, Nihon Fukushi University, Aichi, Japan.|National Center for Geriatrics and Gerontology, Obu City, Aichi, Japan.
Katsunori
K
Kondo
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D044466:Asian People; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007182:Income; D007564:Japan; D008297:Male; D008954:Models, Biological; D009752:Nutritional Status; D012709:Serum Albumin / Q000378:metabolism*; D012959:Socioeconomic Factors
D012709:Serum Albumin