INTRODUCTION
Sciatica (defined as pain radiating from the low back to the leg, usually below the knee) is a disabling condition that causes a major burden to health care and society. Previous evidence of the multifactorial etiology of sciatica comes mostly from cross-sectional studies. The purpose of this population-based study was to identify the independent predictors of sciatica in a multidimensional dataset from early adulthood to midlife. We assessed how a large set of socioeconomic and lifestyle characteristics, psychological symptoms, multimorbidity, and multisite pain predict the incidence of sciatica over a 15-year follow-up.
METHODS
Members of the Northern Finland Birth Cohort 1966 were followed up from the age of 31 to 46. We used multivariable generalized estimation equations (GEE) to analyse if and how socioeconomic characteristics (low education, unemployment, living alone), lifestyle characteristics (overweight, obesity, current smoking, physical inactivity), psychological symptoms (depression, anxiety), multimorbidity, and multisite pain are associated with sciatica. In the multisite pain variable we excluded low back from the list of potential pain sites. We ran univariate models for each predictor and the outcome. As the main approach, we constructed a full multivariable model that included all predictor variables.
RESULTS
The data consisted of 9,099 observations of 6,683 individuals (52% women) at the ages of 31 and/or 46 years. Of the study population, 21% reported sciatic pain at the age of 31 and 37% at the age of 46. Multisite pain at 31 and 46 years was reported by 63% and 64%, respectively. According to the full GEE model, multisite pain was the strongest factor associated with sciatica (odds ratio [OR] 2.61, 95% confidence interval [CI] 2.34‒2.92). In descending order of effect size, older age, low education, psychological symptoms, multimorbidity, overweight, obesity, physical inactivity, and current smoking were positively associated with sciatica (their ORs varied between 1.17 and 2.18). Living alone was negatively associated with sciatica (OR 0.81, 95% CI 0.72‒0.90) (Table1).
DISCUSSION
Our data showed that multisite pain (after the exclusion of low back as a potential pain site) was clearly the factor most strongly associated with sciatic pain. This finding emphasizes the importance of multisite pain for clinical practice when treating patients suffering from sciatica. Recognition of multisite pain could lead to a more successful outcome among sciatic patients.
The effect sizes of other predictors were smaller than that of multisite pain, supporting previous evidence that the etiology of sciatica is multifactorial. These findings could also be exploited to optimize the treatment and rehabilitation of sciatic patients. To our knowledge this is the first study to evaluate the association of multisite pain with sciatica. Our results may have considerable implications for clinical work among patients with sciatica.