Prevalence, Incidence, Comorbidity, and Mortality Rates of Ossification of Posterior Longitudinal Ligament in the Cervical Spine: A Nested Case-Control Cohort Study

OBJECTIVE: To evaluate prevalence, incidence, morbidity, and mortality rates of cervical ossification of posterior longitudinal ligament (OPLL) using data from a 12-year national cohort of 1,025,340 Korean people. METHODS: A nested case-control cohort study was performed from 2002 to 2013 using the insurance claims database provided by the National Health Insurance Service. We examined prevalence and incidence of cervical OPLL. Age-and sex-matched control subjects were randomly extracted, with 10 times the number of OPLL cases. Differences in sex, comorbidity, and relative survival rate compared with control subjects were assessed. RESULTS: Cumulative prevalence was 20,960 per 1,025,340 people for 12 years. Annual incidence was approximately 199-371 per 1 million people. Overall crude mortality rate was 7.64%. Relative survival rate of OPLL cases was not significantly different from control cases. Diabetes, hypertension, cardiovascular disease, and cerebrovascular disease, except renal disease, correlated significantly with OPLL compared with control cases (P < 0.001). Additionally, between dead and surviving patients among OPLL cases, all comorbidities correlated more significantly with death (P < 0.001). Furthermore, between surgery and nonsurgery cases of OPLL, diabetes, hypertension, and renal disease (P < 0.05) were significantly associated with surgery. CONCLUSIONS: Annual incidence of OPLL was 199-371 per 1,025,340 people for 10 years. Diabetes, hypertension, cardiovascular disease, and cerebrovascular disease, except renal disease, correlated significantly with OPLL compared with control cases. Especially, diabetes, hypertension, and renal disease were associated with patients with OPLL who underwent surgery.