Association between obesity and low back pain among Taiwanese adults: does higher economic status alleviate the association?

Presenter: Hsiao-Yun Hu, Yang-Ming University

Abstract

Rationale: Previous studies found that excess body mass may increase the risk of low back pain (LBP), because of lumbar disc disorders, through mechanical load. Ideally, risk from excess mechanical load can be attenuated by use of certain protections. Nevertheless, such protective action requires financial resource, suggesting that people with low economic status may face a higher risk of LBP due to obesity. Investigation of whether higher economic status cushions the risk of LBP associated with obesity helps in understanding socioeconomic inequality in LBP, and throwing light on health policy for reducing inequity in injury.

Objective: To examine whether higher economic status alleviates the risk of LBP associated with obesity.

Methodology: This was a retrospective cohort study. Data from two sources were used: the 2001 Taiwan Health Interview Survey (NHIS) data and the 2002-2004 Taiwan Health Insurance (NHI) claim data. Our sample consisted of 12,862 adults who were aged 18 years or older in 2001 and gave consent to the linkage of their survey data with corresponding NHI claims data. We defined “obesity” according to the WHO-Asia Pacific categories of Body Mass Index (BMI in kg/m2). Cox’s proportional hazards regression was used to identify factors associated with LBP. In addition to the obese condition, factors controlled for in the multivariate analysis included sex, age, ethnicity, education, occupation, the amount of physical activity, smoking status, and the level of alcohol consumption. Separate models were estimated for persons with high, middle and low economic status.

Results: Being overweight or obese was associated with a higher risk of LBP. For persons with high or middle economic status, the level of risk of being overweight (BMI=23.0~24.9) and that of being obese (BMI=25.0 or over) were close, and the level of risk was moderate (HR=1.19 to 1.27). For persons with low economic status, the level of risk of being overweight and that of being in Class I of obesity (BMI=25.0~29.9) were also both moderate (HR=1.28), while the level for being in Class II of obesity (BMI=30.0 or over) was higher (HR=1.73).

Conclusions: Persons with low economic status have a higher risk of LBP associated with obesity. Policy intervention should be taken to reduce such inequality, and more research is required to identify aids poor people need in order to prevent excess risks of being injured.