Association between cardiorespiratory fitness and low back pain is anxiety-dependent: A prospective cohort study among adults and older adults.

To investigate the relationship between low back pain and cardiorespiratory fitness (CRF) among participants with and without self-report anxiety. Participants were 13,080 individuals (86.6% men; 44.7 ± 9.3 years). CRF was quantified as maximal treadmill test duration and was grouped for analysis as low (lowest 20% of treadmill test duration), moderate (middle 40%), and high (upper 40%). Cox regression analysis was used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) between low back pain and CRF according to the presence/absence of self-report anxiety. During an average of 5.7 ± 5.1 years of follow-up, 2,965 cases of low back pain were identified. Participants with self-report anxiety and low CRF had 3.7 times (HR: 3.7; 95%CI: 1.7-8.2) more risk for having low back pain when compared with participants with self-report anxiety and high CRF. Additionally, among participants with self-reported anxiety, moderate CRF was associated with an 70% greater risk of having low back pain than those with high CRF (HR: 1.7; 95%CI: 1.1-3.2). For participants without self-reported anxiety, no association was found between the risk of having low back pain and CRF. According to the results identified in the present study, participants with self-reported anxiety who had low and moderate CRF had higher risks of low back pain than those with high CRF.