Background There is limited information on the role of low socioeconomic status (SES) in the development of new chronic kidney disease (CKD) in the general population, especially from developing countries. This study will test the hypothesis that low SES increases the risk of incidence of decreased glomerular filtration rate (GFR, used as an estimate for CKD) in a Thai worker cohort.
Method In this prospective, longitudinal observational study, we evaluated the association of income and educational attainment on incident decreased GFR (iGFR <60 mL/min/1.73 m2) over a 27-year period in employees of Electricity Generating Authority of Thailand. In 1985, subjects participated in a health survey and were re-examined in 1997, 2002, 2007 and 2012. Education was classified into three categories: low, 0–8th grade; medium, 9–12th grade; and high, >12th grade. Income was categorised as follows: low <10 000 Thai Baht (THB)/month; medium, 10 000–20 000 THB/month; and high, >20 000 THB/month. HRs of iGFR<60 mL/min/1.73 m2 were estimated using Cox interval-censored models with high income or education as the reference groups after adjustments for clinical risk factors.
Results Participants (n=3334) were followed for 23 (15, 27) years. When evaluated separately, both education and income were risk factors for iGFR<60 mL/min/1.73 m2 (adjusted HR education: medium—1.26 (95% CI 1.13 to1.42) and low—1.57 (95% CI 1.36 to 1.81) and adjusted HR income: medium—1.21 (95% CI 0.97 to 1.50) and low—1.47 (95% CI 1.18 to 1.82)). When both income and education were included together, low and medium education remained independently associated with iGFR<60 mL/min/1.73 m2.
Conclusions Low education was independently associated with increased risk of decreased GFR in a Thai worker population. Strategies to identify risk factors among low SES may be useful to prevent early CKD.
- BLOOD PRESSURE
- Clinical epidemiology
- Epidemiology of chronic non-communicable diseases
- LONGITUDINAL STUDIES
- CHRONIC DI
- Cardiovascular disease
- Health inequalities
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Contributors PV, CK, KS were involved in the data analysis. PV, NT, TT, KD were involved in subject recruitment, outcome assessment and database management. AC and SV were involved in laboratory standardisation and measurements of serum creatinine. PS is the project leader and is responsible for co-ordination and funding of the project. All authors were involved in the preparation of the manuscript and approved the final version.
Funding This article was funded by the Faculty of Medicine, Ramathibodi Hospital, Mahidol University, the Higher Education Research Promotion and National Research University Development, Office of the Higher Education Commission, the National Research Council, the Thai Health Foundation, the Thai Heart Association and the Thailand Research Fund.
Competing interests None declared.
Patient consent for publication Not required.
Data sharing statement All data relevant to the study are included in the article or uploaded as supplementary information.
Provenance and peer review Not commissioned; externally peer reviewed.