NSAID Use Attenuates the Protective Effect of Physical Activity on Chronic Low Back Pain: A Cross-Sectional Analysis of NHANES 2009–2010

Background: Chronic low back pain (CLBP) is a leading cause of disability worldwide, with exercise endorsed as first-line treatment and non-steroidal anti-inflammatory drugs (NSAIDs) among the most used pharmacologic options. These interventions are frequently combined in clinical practice, yet their synergistic effects remain unclear. To evaluate whether NSAID use modifies the association between physical activity (PA) and CLBP using nationally representative data from NHANES 2009–2010. Methods: We analyzed 988 adults aged ≥20 years with complete data on chronic low back pain, physical activity, medication use, and modeled covariates. Results: Among participants not using NSAIDs, moderate recreational physical activity was associated with lower odds of CLBP (adjusted OR = 0.47, 95% CI 0.25–0.91; p = 0.029). Active transport showed a similar direction but was not statistically significant (OR = 0.38, 95% CI 0.13–1.12; p = 0.074). In interaction models, active transport x aspirin was associated with higher odds of CLBP (OR = 2.24, 95% CI 1.02–4.90; p = 0.044), and moderate recreational PA x any NSAID use was also associated with higher odds of CLBP (OR = 2.26, 95% CI 1.01–5.06; p = 0.047). Subgroup analyses were exploratory and heterogeneous, including a significant potential protective interaction (OR ≈ 0.19, 95% CI 0.06–0.69; p = 0.015). Conclusions: In a nationally representative sample, NSAID use appeared to modify the association between physical activity and chronic low back pain. These findings are exploratory and hypothesis-generating. Therefore, longitudinal studies are needed to clarify the temporal and causal relationships and the potential influence of NSAIDs.