Underweight as a risk factor for vertebral fractures in the South Korean population.

BACKGROUND CONTEXT: Being underweight is a known risk factor for osteoporosis and sarcopenia that is strongly associated with vertebral fractures, particularly in the elderly. Being underweight can accelerate bone loss, contribute to impaired coordination, and increase fall risk in the elderly and the general population. PURPOSE: This study aimed to identify the degree of underweight as a risk factor for vertebral fractures in the South Korean population. STUDY DESIGN: Retrospective cohort study based on national health insurance database. PATIENT SAMPLE: Participants were included from nationwide regular health check-ups conducted by the Korean National Health Insurance Service in 2009. Participants were followed up from 2010 to 2018 to identify the incidence of newly developed fractures. OUTCOME MEASURES: The incidence rate (IR) was defined as the incident per 1,000 person-years (PY). Vertebral fracture development risk was analyzed using Cox proportional regression analysis. Subgroup analysis was performed based on several factors, including age, sex, smoking status, alcohol consumption, physical activity, and household income. METHODS: Based on body mass index, the study population was categorized into normal weight (18.50-22.99 kg/m2), mild underweight (17.50-18.49 kg/m2), moderate underweight (16.50-17.49 kg/m2), and severe underweight (<16.50 kg/m2) groups. Cox proportional hazards analyses were performed to calculate the hazard ratios for vertebral fractures based on the degree of underweight with respect to normal weight to identify the associated risk. RESULTS: This study evaluated 962,533 eligible participants, of whom 907,484 were classified as normal weight, 36,283 as mild underweight, 13,071 as moderate underweight, and 5,695 as severe underweight. The adjusted hazard ratio of vertebral fractures increased as the degree of underweight increased. Severe underweight was associated with a higher likelihood of vertebral fracture. The adjusted hazard ratio was 1.11 (95% confidence interval [CI], 1.04-1.17) in the mild underweight group, 1.15 (1.06-1.25) in the moderate underweight group, and 1.26 (1.14-1.40) in the severe underweight group when compared with the normal weight group. CONCLUSIONS: Underweight is a risk factor for vertebral fractures in the general population. Furthermore, severe underweight was associated with a higher risk of vertebral fractures, even after adjustment for other factors. Clinicians could provide real-world evidence that being underweight carries the risk of vertebral fractures.

The Influence of Rheumatoid Arthritis on Higher Reoperation Rates over Time Following Lumbar Spinal Fusion-A Nationwide Cohort Study.

This study aimed to compare the rates of reoperation over time following first lumbar fusion in rheumatoid arthritis (RA) patients and non-RA patients. This study was conducted using Korean Health Insurance Review and Assessment (HIRA) data. We identified the RA group as 2239 patients who underwent their first lumbar fusion with RA and the control group as 11,195 patients without RA. This reflects a ratio of 1:5, and the participants were matched by sex, age, and index surgery date. The index dates were between 2012 and 2013. When comparing the rate of patients undergoing reoperation, the adjusted HR was 1.31 (95% CI: 1.10−1.6) in the RA group (p = 0.002). In terms of the three time intervals, the values in the time frames of <3 months and 3 months−1 year were not statistically significant. However, at 1 year post-surgery, there was a higher risk of reoperation in the RA group, as demonstrated by the Kaplan−Meier cumulative event analysis. This higher risk of reoperation continued to increase throughout 5 years of follow-up, after which it was stable until the last follow-up at 7 years. This population-based cohort study showed that the RA patients had a 1.31 times higher risk of reoperation following lumbar fusion than did the controls. This difference was more pronounced at 1 year post-surgery.