Physical Fitness and Activity Levels as Predictors of Subjective Well-Being in Youths With Type 1 Diabetes Mellitus: A 2-Year Longitudinal Analysis of the Diactive-1 Cohort Study

Subjective well-being (SWB), including cognitive and affective components, may be influenced by the management of type 1 diabetes mellitus (T1DM). Physical fitness and adherence to physical activity (PA) are associated with better glycaemic stability and diabetes management. However, the relationship with SWB is not yet understood. The aim of the study was to determine the relationship between physical fitness, PA, and SWB over two years in youths with T1DM. This longitudinal study involved 83 participants (aged 6–18 years; 44.6% girls) from the Diactive-1 Cohort. Physical fitness was assessed by spirometry (peak oxygen consumption) and dynamometry (handgrip strength). PA domains were measured using triaxial accelerometers, whereas the number of days participating in muscle-strengthening activities was assessed using a question. The Cuestionario Único de Bienestar Escolar was used to determine SWB. Glycaemic stability was determined when glycosylated hemoglobin < 7%, coefficient of variability ≤ 36%, and time-in-range target > 70% were met. The linear mixed models used considered three assessments and subject variability, showing significant associations between overall physical fitness (unstandardized beta coefficient [B] = 1.778, 95% confidence interval [CI] 0.413–3.158; p = 0.012) and total PA (B = 0.034, 95% CI 0.005–0.063; p = 0.020) with SWB. Although time did not moderate the association with physical fitness (p = 0.116), this was true for PA only in the second year (p = 0.020). In contrast, glycaemic stability did not moderate the associations (p > 0.05). In conclusion, physical fitness and PA are associated with greater SWB in young people with T1DM, which may play a role in the psychological aspects of disease management.