Does income matter for troublesome neck pain? A population-based study on risk and prognosis.

BACKGROUND Studies have shown associations between higher income and better health, but income has not been studied in relation to neck pain. The aims of this cohort study were to assess the sex-specific role of disposable income for onset and prognosis of neck pain in the general population and if economic stress influences such potential associations. METHODS Two subcohorts were identified in the Stockholm Public Health Cohort with data from 2002. Cohort I (risk cohort) included persons without neck pain (n=8348). Cohort II (prognostic cohort) included persons with occasional neck pain during the previous 6 months (n=10 523). Both cohorts were assessed for long duration troublesome neck pain (LDNP) in 2007. Individual income was defined as aggregated annual family income in 2002 with each family member assigned a weighted consumption share, based on salary, pensions and social benefits. LDNP in 2007 was defined as having had troublesome neck pain lasting for three or more consecutive months the previous 5 years. Association between income and LDNP, considering potential confounding, was investigated by multivariable logistic regression. Economic stress was tested as effect modifier between income and LDNP. RESULTS In both cohorts, associations were found between lower income and a higher risk for LDNP. The results were similar between the sexes. Economic stress modified the associations in both cohorts. CONCLUSIONS Low income may be a risk as well as prognostic factor for developing LDNP. Furthermore, the results indicate that economic stress may be an underlying factor to consider when studying associations between income and neck pain.