Cardiorespiratory fitness in individuals with type 2 diabetes mellitus: a systematic review and meta-analysis

OBJECTIVE: To conduct a systematic review and meta-analysis assessing the cardiorespiratory fitness (CRF) among individuals with and without type 2 diabetes MATERIALS AND METHODS: The current review was registered in PROSPERO under the number CRD42018082718. MEDLINE, EMBASE, and Cochrane Library databases were searched from inception through February 2022. Eligibility criteria consisted of observational or interventional studies that evaluated CRF through cardiopulmonary exercise testing or six-minute walk test in individuals with type 2 diabetes compared with individuals without type 2 diabetes. For data extraction, we used baseline CRF assessments of randomized clinical trials or follow-up CRF assessments in observational studies. We performed a meta-analysis using maximal oxygen consumption (VO(2)max), and distance walked in the 6MWT as primary outcomes. They were extracted and expressed as mean differences (MDs) and 95% CIs between treatment and comparator groups. The meta-analysis was conducted using Review Manager (RevMan) software. RESULTS: Out of 8,347 studies retrieved, 77 were included. Compared with individuals without type 2 diabetes, individuals with diabetes achieved a lower VO(2)max (−5.84 mL.kg(−1).min(−1), 95% CI −6.93, −4.76 mL.kg(−)(1).min(−1), p = <0.0001; I(2) = 91%, p for heterogeneity < 0.0001), and a smaller distance walked in 6MWT (−93.30 meters, 95% CI −141.2, −45.4 meters, p > 0.0001; I(2): 94%, p for heterogeneity < 0.0001). CONCLUSION: Type 2 diabetes was associated with lower cardiorespiratory fitness, as observed by lower VO(2)max on maximal tests, and smaller distance walked in 6MWT, however the quality of studies was low.