Association of ossification of the posterior longitudinal ligament with ischemic stroke in Korea: a nationwide longitudinal cohort study

Objective This nationwide longitudinal follow-up study investigated the relationship between ischemic stroke and ossification of the posterior longitudinal ligament (OPLL). Methods Patient data were gathered from the National Health Insurance Service Health Screening cohort. Patients with OPLL were identified by the International Classification of Diseases, 10th revision codes M48.8, M48.81, M48.82, and M48.83. Age- and sex- stratified matching at a 1:5 ratio was used to include a total of 1,289 patients with OPLL and 6,445 controls from January 1, 2004 to July 31, 2015. The Kaplan-Meier method was used to calculate the ischemic stroke incidence rate for each group. Cox proportional-hazards regression analysis was used to estimate the hazard ratio of ischemic stroke. Results Ischemic stroke occurred in 92 (7.1%) patients in the OPLL group and 162 (2.5%) patients in the control group had ischemic stroke. Adjusting for age and sex, the hazard ratio of ischemic stroke in the OPLL group was 4.692 (95% confidence interval [CI], 3.610-6.099). The hazard ratio of ischemic stroke in the OPLL group was 5.008 (95% CI, 3.845-6.516) when considering additional income and underlying diseases. The subgroup analysis showed higher risk ratios of ischemic stroke in all OPLL patient subgroups defined in terms of sex, age, diabetes, hypertension, and dyslipidemia. Conclusion The incidence rate of ischemic stroke was elevated in patients with OPLL according to this nationwide longitudinal study. Keywords: Ossification of posterior longitudinal ligament; Ischemic stroke; Population; Epidemiology