# Effects of Photobiomodulation on Metabolic, Inflammatory, and Neurological Outcomes in Type 2 Diabetes: A Systematic Review and Meta-Analysis

## TL;DR

This review finds that photobiomodulation therapy may slightly improve periodontal health in people with type 2 diabetes, but evidence for broader benefits is weak and needs more research.

## Contribution

The study is the first to systematically evaluate PBMT's effects on multiple outcomes in T2DM using a meta-analysis and narrative synthesis.

## Key findings

- PBMT showed modest improvements in periodontal outcomes like clinical attachment level and probing depth.
- Effects on glycemic control, inflammation, and neurological function were inconsistent and short-term.
- The overall certainty of evidence was low, and clinical significance of findings remains uncertain.

## Abstract

Type 2 diabetes mellitus (T2DM) is a global health burden characterized by hyperglycemia, oxidative stress, and systemic inflammation, which leads to complications that remain insufficiently managed by standard therapies. Photobiomodulation therapy (PBMT) has been proposed to be a complementary approach, but its effects in T2DM are unclear. We conducted a systematic review and meta-analysis of randomized controlled trials to evaluate the effects of PBMT on metabolic, inflammatory, and neurological outcomes in adults with T2DM. Five databases were searched until June 2025 (PROSPERO CRD420251083550) for relevant studies. Metabolic, inflammatory, and neurological outcomes were defined a priori as primary outcomes and were synthesized narratively due to substantial heterogeneity and incomplete reporting that precluded valid quantitative pooling. Although periodontal outcomes were not predefined as primary outcomes, they were reported in multiple trials; thus, these were analyzed quantitatively as secondary outcomes where sufficient homogeneity enabled meta-analysis. The narrative synthesis of primary outcomes showed inconsistent and largely short-term effects on glycemic control, systemic inflammation, and neurological function. In contrast, meta-analysis of secondary periodontal outcomes demonstrated modest but statistically significant improvements in clinical attachment level (−0.21 mm) and probing depth (−0.25 mm), with no effect on plaque index. Overall, the certainty of the evidence was low. PBMT may offer statistically significant but small adjunctive periodontal effects in adults with T2DM. However, the certainty of evidence is low, and these effects are unlikely to be clinically meaningful in isolation. Evidence for systemic metabolic, inflammatory, and neurological outcomes is preliminary and requires confirmation in larger, standardized RCTs.