**5. Conclusions**

Based on data close to that of the general population, this cross-sectional study confirmed that LBP tended to increase with age in both men and women. Moreover, a high PI-LL mismatch was significantly associated with LBP development in the healthy community-dwelling elderly, which might serve as a simple indicator of health risk and aid in the prevention of back problems in this age group.

**Author Contributions:** Conceptualization, M.U. and S.I.; methodology, M.U., S.I. and J.T.; validation, M.U., and S.I.; formal analysis, M.U. and S.I.; investigation, M.U., S.I., H.H., J.T. and H.K.; data curation, M.U., S.I., H.H., J.T. and H.K.; writing—original draft preparation, M.U.; writing—review and editing, S.I., H.H., J.T. and H.K.; and supervision, H.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by a gran<sup>t</sup> from the Japan Orthopaedics and Traumatology Research Foundation, Inc. (no. 339), project research funds from the Japanese Orthopaedic Association, a research fund from the Japanese Society for Musculoskeletal Medicine, and a research fund from The Nakatomi Foundation.

**Institutional Review Board Statement:** The study was conducted according to the guidelines of the Declaration of Helsinki, and approved by the Institutional Review Board of Shinshu University Hospital (no. 2792).

**Informed Consent Statement:** Informed consent was obtained from all subjects involved in the study. Written informed consent has been obtained from the patients to publish this paper.

**Data Availability Statement:** The complete database of the cohort can be accessed at the Zenodo repository (doi.org/10.5281/zenodo.5512411).

**Conflicts of Interest:** The authors declare no conflict of interest.
