Higher levels of cardiorespiratory fitness may reduce the risk for type 2 diabetes in adults and can reduce the diabetogenic effects of statin use, according to findings published in Obesity .
“In addition to being able to predict the risk of all-cause and disease-specific mortality, a large body of literature indicates that [cardiorespiratory fitness] might be associated with the risk of type 2 diabetes. … Yet concerns remain as to whether a similar association exists in statin users, who are vulnerable to the development of type 2 diabetes, and whether a higher level of [cardiorespiratory fitness] would attenuate or eliminate the increased risk of type 2 diabetes in statin users compared with individuals not taking statins,” Zilin Sun , MD, PhD, of the department of endocrinology at Zhongda Hospital, Medical School of Southeast University, in Nanjing, China, and colleagues wrote.
Sun and colleagues conducted a meta-analysis of 15 cohort studies published up to May 2018. Studies were included if they reported an association between cardiorespiratory fitness and risk for type 2 diabetes and measured cardiorespiratory fitness by an exercise test. Risk reduction of type 2 diabetes was calculated by 1 metabolic equivalent (MET), which is equal to 3.5 mL/min/kg of oxygen consumption, according to the researchers.
Based on the pooled data, researchers observed a dose-response relationship between cardiorespiratory fitness and type 2 diabetes risk ( P < .01) with each 1-MET increase in cardiorespiratory fitness associated with an HR of 0.9 for type 2 diabetes (95% CI, 0.86-0.94). A similar type 2 diabetes HR (0.91; 95% CI, 0.88-0.95) for each 1-MET increase was found in six studies with or without BMI adjustment.
Researchers determined the risk for type 2 diabetes corresponding to three categories of cardiorespiratory fitness (high, moderate and low). The risk for developing diabetes was 38% lower for participants in the high category (HR = 0.62; 95% CI, 0.49-0.77) compared with those in the low category, who were used as reference. The risk was 18% lower in participants with moderate cardiorespiratory fitness (HR = 0.82; 95% CI, 0.73-0.93) compared with the low category.
Participants were considered unfit if they fell into the first quartile or tertile of cardiorespiratory fitness in a study. All other participants were considered fit, with participants who met that criterion and had normal weight used as reference. Participants with normal weight who were considered unfit were at a higher risk for developing type 2 diabetes (HR = 1.26; 95% CI, 1.06-1.52) compared with participants with normal weight who were considered fit. Participants with obesity also had a higher risk compared with normal-weight fit participants regardless of whether they were in fit (HR = 2.05; 95% CI, 1.55-2.7) or unfit (HR = 2.98; 95% CI, 1.97-4.5).
“These findings undoubtedly highlight the importance and necessity of improving [cardiorespiratory fitness] in the clinical practice,” the researchers wrote. “However, it seems likely that interventions aiming to promote weight loss are more valuable as recommendations than interventions to improve [cardiorespiratory fitness] in reducing the risk of type 2 diabetes.”
Statin use was considered in three of the studies. With a total of 12,311 combined statin users, the HR for type 2 diabetes based on each 1-MET increase in cardiorespiratory was 0.92 (95% CI, 0.87-0.97), with the researchers noting a dose-response relationship ( P < .01). Compared with participants who did not use statins, statin users had a higher risk for developing type 2 diabetes if they had low (HR = 1.9; 95% CI, 1.39-2.59) or moderate (HR = 1.22; 95% CI, 1.07-1.39) levels of cardiorespiratory fitness, but a lower risk when coupled with high cardiorespiratory fitness (HR = 0.91; 95% CI, 0.72-1.15).
“[These findings] may help ameliorate the ongoing uncertainties about the increased risk of type 2 diabetes resulting from statin use, in particular when statins are recommended for the primary prevention of cardiovascular events, if approaches designed to improve [cardiorespiratory fitness], such as attending exercise training or increasing physical activity, are implemented,” the researchers wrote. – by Phil Neuffer
Disclosure s: The authors report no relevant financial disclosures
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