**5. Conclusions**

This study represents the first attempt to investigate the clinical prognostic feasibility of applying the PEI, and demonstrates enhanced sensitivity in differentiating between diabetic subjects without DPN and diabetic subjects with DPN within six years after baseline measurement, compared to single-scale indices (i.e., LHR and PWVmean) and multiple temporal-scale indices (i.e., MEISS and MEILS). Our findings sugges<sup>t</sup> that diabetic patients with smaller PEI values are more prone to developing DPN, which is of potential importance for application in the area of the point-of-care diagnostic devices.

**Author Contributions:** Conceptualization, H.-T.W.; Data curation, N.T., W.-R.H., S.-Y.W., and J.-J.C.; Formal analysis, N.T. and H.-T.W.; Funding acquisition, H.-C.W.; Investigation, N.T., M.-X.X., X.-J.T., and H.-T.W.; Methodology, N.T., J.-J.C., and H.-T.W.; Project administration, H.-C.W. and H.-T.W.; Resources, H.-C.W.; Software, N.T., W.-R.H., S.-Y.W., and M.-X.X.; and Supervision, H.-C.W., X.-J.T., and H.-T.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by North Minzu University Scientific Research Projects (Major projects No. 2019KJ37), National Natural Science Foundation of China (No. 61861001), Ningxia Municipal Health Commission Project (No. 2018NW007), and "Tian Cheng Hui Zhi" Innovation & Education Fund of Chinese Ministry of Education (No. 2018A01016).

**Acknowledgments:** The authors are grateful for the support of Texas Instruments, Taiwan, in sponsoring the MSP tools and assisting in developing novel signal-processing techniques as a contribution to preventive medicine in this study. The authors would like to thank the Guest editor and Reviews for their insightful recommendations, which have contributed greatly to the improvement of this work.

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