Temporal stability in the prevalence and pattern of co-occurring musculoskeletal pain among people with persistent low back pain: population-based data from the Norwegian HUNT Study, 1995 to 2019.

People with persistent low back pain (LBP) often report co-occurring persistent musculoskeletal (MSK) pain in other body regions that may influence prognosis as well as treatment approaches and outcomes. This study describes the prevalence and patterns of co-occurring persistent MSK pain among people with persistent LBP based on consecutive cross-sectional studies over 3 decades in the population-based HUNT Study, Norway. The analyses comprised 15,375 participants in HUNT2 (1995-1997), 10,024 in HUNT3 (2006-2008), and 10,647 in HUNT4 (2017-2019) who reported persistent LBP. Overall, ∼90% of participants in each of the HUNT surveys with persistent LBP reported persistent co-occurring MSK pain in other body sites. The age-standardized prevalence of the most common co-occurring MSK pain sites was consistent across the 3 surveys: 64% to 65% report co-occurring neck pain, 62% to 67% report shoulder pain, and 53% to 57% report hip or thigh pain. Using latent class analysis (LCA), we identified 4 distinct patterns of persistent LBP phenotypes that were consistent across the 3 surveys: (1) "LBP only," (2) "LBP with neck or shoulder pain," (3) "LBP with lower extremity or wrist or hand pain," and (4) "LBP with multisite pain," with conditional item response probabilities of 34% to 36%, 30% to 34%, 13% to 17%, and 16% to 20%, respectively. In conclusion, 9 of 10 adults in this Norwegian population with persistent LBP report co-occurring persistent MSK pain, most commonly in the neck, shoulders, and hips or thighs. We identified 4 LCA-derived LBP phenotypes of distinct MSK pain site patterns. In the population, both the prevalence and pattern of co-occurring MSK pain and the distinct phenotypic MSK pain patterns seem stable over decades.