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
Disclosures: The authors report no relevant financial disclosures