Ossification of the posterior longitudinal ligament of the spine: A case-control risk factor study

Study Design. A case-control study. Objectives. To determine the risk factors for ossification of the posterior longitudinal ligaments (OPLL) of the spine. Summary of Background Data. Previous epidemiologic studies conducted in Japan showed consuming vegetable protein and salt was a risk factor for OPLL. Dietary habits of the Taiwanese and Japanese people are similar. Whether the similar dietary habits play an important role in the high prevalence of OPLL in Taiwan was of interest. Methods. A case-control study was conducted in a tertiary teaching hospital. The study included 98 consecutive cervical spine patients with OPLL, with 98 age-matched patients with cervical spondylosis serving as control subjects. Radiologic examinations, clinical interviews, physical examinations, and risk factor questionnaires were administered to all the participants. Results. Compared with incidence in the control patients, the frequency of the ossification of the anterior longitudinal ligament was significantly higher in OPLL patients with OPLL (31% vs. 19%; P = 0.049), but there was no difference in incidence of ossifications of the ligamentum flavum (13.3% vs. 16.3%; P = 0.546). More OPLL patients preferred a high-salt diet (OPLL/CS, no:somewhat:yes = 23/38:18/25:57/35);, X² for trend = 6.3; P = 0.001) and picked foods (OPLL/CS, no:somewhat:yes = 39/56:11/11:48/31; X² for trend = 6.7; P = 0.0099). Fewer patients with OPLL consumed meat daily (63%. vs. 79%; P = 0.018). High-salt diet (odds ratio = 2.62) and daily meat intake (odds ratio = 0.39) showed persistent association with OPLL in a multivariate logistic regression. Conclusions. The similar dietary habits, particularly a high- salt and low meat intakes, may partially explain the high prevalence of OPLL in Taiwan and Japan. Modifying dietary habits may help prevent this disease, especially in those high-risk populations.