Vivekanantham A, et al. - Studies quantifying the association between primary chronic headaches and persistent low back pain (LBP) are systematically reviewed. Searching five electronic databases, researchers included 14 studies sizes of the studies ranged from 88 participants to a large international study with 404,206 participants. The analysis suggests that persistent LBP is positively associated with primary headache disorders. Diversity of populations, study designs and uncertainly about headache and LBP definitions limited the quality of the review findings.