24-Hour Physical Behavior Patterns and Cutaneous Microvascular Reactivity in Adults Living with Type 1 Diabetes: A Cross-Sectional Study

Background/Objectives: Microvascular dysfunction is an early manifestation of vascular impairment in type 1 diabetes (T1D). Although physical activity may improve vascular health, the relationship between integrated 24 h physical behavior patterns and microvascular function remain unclear. This study evaluated the association between 24 h physical behavior patterns and cutaneous microvascular reactivity in adults living with T1D, and examined their relationship with endothelium-dependent microvascular function. Methods: This cross-sectional study included 92 adults with T1D. Physical activity and sedentary behavior were assessed through accelerometry and combined with self-reported sleep duration. Participants were classified into three clusters using partitioning around medoids. Cutaneous microvascular reactivity was assessed through laser speckle contrast imaging, with post-occlusive reactive hyperemia (PORH) peak and amplitude of cutaneous vascular conductance (CVC) as primary outcomes. Acetylcholine (ACh)-induced responses were evaluated as exploratory outcomes. Generalized linear models with progressive adjustment were used to examine the associations. Results: Three distinct behavioral patterns were identified. In the fully adjusted model, compared with Cluster 3, the estimates for PORH peak CVC were β = −0.02 (95% CI: −0.16 to 0.11) for Cluster 1 and β = 0.01 (95% CI: −0.13 to 0.16) for Cluster 2. Similar null findings were observed for PORH amplitude CVC and ACh-derived outcomes. Sensitivity analyses including microvascular burden did not alter the findings. Conclusions: In adults living with T1D, 24 h physical behavior patterns were not associated with microvascular reactivity or endothelium-dependent function. These findings suggest that daily behavior distribution may not be strongly related to microvascular responses, although subtle effects cannot be excluded. Longitudinal studies using fully device-based 24 h assessments are warranted.