Individuals with diabetes may want to dust off their bicycles and strap on a helmet—results from a prospective cohort study suggested that cycling was linked to lower all-cause and cardiovascular disease (CVD) mortality among patients with diabetes, independent of other physical activities.
Previous research reported inverse associations between overall physical activity, leisure-time physical activity (LTPA), and walking with all-cause and CVD mortality in patients with diabetes, Mathias Ried-Larsen, PhD, of the Center for Physical Activity Research in Copenhagen, Denmark, and colleagues explained in JAMA Internal Medicine. However, many patients have difficulty meeting the recommended volume and intensity of physical activity necessary to attenuate CVD risks, with many citing lack of time as a barrier.
Thus, incorporating physical activity into everyday life may be ideal for these patients. Ried-Larsen and colleagues hypothesized that cycling—an activity that can replace motorized transportation, incorporates moderate-to-high intensity physical activity, and has an established benefit on all-cause mortality among the general population—may be a feasible strategy for this patient population, particularly since cycling is reportedly one of the preferred activities among individuals with type 2 diabetes (T2D).
For their analysis, Ried-Larsen and colleagues assessed the association between cycling and all-cause/CVD mortality in individuals with diabetes, as well as the associations between change in cycling over a 5-year period and all-cause/CVD mortality.
The study authors found that patients with diabetes who engaged in cycling saw a reduction in all-cause mortality risk of at least 24% compared to non-cyclists, independent of other physical activity and other putative confounders. Also, taking up cycling over a 5-year period was associated with an increased risk reduction of at least 35% compared to noncyclists. However, the researchers added, “the dose-response relationships were ambiguous,” and further studies “with repeated measurement of cycling and documentation of cycling-related accidents are needed to elaborate on the dose-response relationship between cycling and mortality.”
In an editor’s note accompanying the study, Rita F. Redberg, MD, MSc, of the University of California in San Francisco and Editor of JAMA Internal Medicine, Eric Vittinghoff, PhD, of the University of California and Statistical Editor at JAMA Internal Medicine, and Mitchell H. Katz, MD, of NYC Health + Hospitalas in New York City and Deputy Editor of JAMA Internal Medicine, wrote that, “[d]espite the limitations of an observational study and the possible selection bias of people who are able to cycle, it is important to share this evidence for the potentially large health benefits of cycling, which almost surely generalize to persons without diabetes. Furthermore, there are environmental benefits to increasing the use of cycling for commuting and other transport because cycling helps to decrease the adverse environmental and health effects of automobile exhaust.”
They added that the study by Ried-Larsen et al “strengthens the epidemiologic data on cycling and strongly suggests that it may contribute directly to longer and healthier lives. As avid and/or aspiring cyclists ourselves, we are sold on the mental and physical benefits of getting to work and seeing the world on 2 wheels, self-propelled, and think it is well worth a try.”
For their prospective analysis, Ried-Larsen and colleagues included 7,459 adults with diabetes (mean [SD] age, 55.9 (7.7) years; 3,924 [52.6%] female) from the European Prospective Investigation into Cancer and Nutrition study, which was conducted at 23 centers in 10 Western European countries (France, Italy, Spain, U.K., the Netherlands, Greece, Germany, Sweden, Denmark, and Norway).
Dietary intake was assessed via questionnaire at baseline (1992-1998), as was information about physical activity, which included information regarding duration and frequency of both leisure time and occupational physical activity. “Weekly time spent cycling to and/or from work and leisure time during winter and summer was averaged into a single variable of total annual cycling time and then categorized as 0, 1 to 59, 60 to 149, 150 to 299, and 300 or more min/wk,” they explained.
Total cycling time was categorized as 0, 1 to 59, 60 to 149, 150 to 299, and 300 or more min/wk. Changes in total cycling time from baseline to the second examination (1996-2011) were categorized based on total time spent cycling: 1) noncycling: participants who reported zero minutes of cycling at both examinations; (2) stopped cycling: participants who reported cycling (any amount) at baseline but not at the second examination; (3) started cycling: participants who did not report cycling at baseline but did report cycling (any amount) at the second examination; or (4) maintained cycling: those who were consistent cyclists at both examinations.”
They also assessed LTPA energy expenditure for non-cycling activities at both examinations as the sum of energy expenditures from gardening, do-it-yourself activities, stair climbing, housework activities, walking, and sports. Occupational physical activity was reported in categories of sedentary occupation, standing occupation, manual or heavy manual work, or non-worker.
The primary and secondary outcomes were all-cause and CVD mortality, respectively, adjusted for other physical activity modalities, diabetes duration, and sociodemographic and lifestyle factors.
“During 110,944 person-years of follow-up, 1,673 deaths from all causes were registered,” the study authors reported. “Compared with the reference group of people who reported no cycling at baseline (0 min/wk), the multivariable-adjusted hazard ratios for all-cause mortality were 0.78 (95% CI, 0.61-0.99), 0.76 (95% CI, 0.65-0.88), 0.68 (95% CI,0.57-0.82), and 0.76 (95% CI, 0.63-0.91) for cycling 1 to 59, 60 to 149, 150 to 299, and 300 or more min/wk, respectively. In an analysis of change in time spent cycling with 57,802 person-years of follow-up, a total of 975 deaths from all causes were recorded. Compared with people who reported no cycling at both examinations, the multivariable-adjusted hazard ratios for all-cause mortality were 0.90 (95% CI, 0.71-1.14) in those who cycled and then stopped, 0.65 (95% CI, 0.46-0.92) in initial noncyclists who started cycling, and 0.65 (95% CI, 0.53-0.80) for people who reported cycling at both examinations. Similar results were observed for CVD mortality.”
Ried-Larsen and colleagues pointed out that the association between cycling and call-cause/CVD mortality in this study “was of the same magnitude and direction as observed in the healthy population.” However, when they conducted post hoc modeling of the dose-response relationship with baseline cycling as a continuous variable for both all-cause and CVD mortality, the shapes of the dose-response curves were ambiguous, with an uptick in hazard ratios for both all-cause and CVD mortality at higher volumes of cycling.
These upticks, noted Ried-Larsen and colleagues, may be partially attributable to increased risk of fatal accidents and exposure to air pollutants, as well as potential adverse events associated with very high volumes of physical activity, but they argued that the most likely explanation was a measurement error on the exposure variable.
Study limitations included that the observational design limit causal inferences; an inability to distinguish between type 1 and type 2 diabetes; the decision to include those with both confirmed and self-reported diabetes increased the risk of misclassification; and the results may not be generalizable to individuals using electric cycles.
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Results from a prospective cohort study suggested that cycling was linked to lower all-cause and cardiovascular disease (CVD) mortality among patients with diabetes, independent of other physical activities.
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Note that the dose-response relationships between cycling and all-cause/CVD mortality were ambiguous, and further studies with repeated measurement of cycling and documentation of cycling-related accidents are needed to elaborate on the dose-response relationship between cycling and mortality.
John McKenna, Associate Editor, BreakingMED™
This work was supported by the Health Research Fund of Instituto de Salud Carlos III; regional governments of Andalucía, Asturias, Basque Country, Murcia, and Navarra; and the Catalan Institute of Oncology. The Centre for Physical Activity Research is supported by a grant from TrygFonden.
Ried-Larsen reported personal fees from Novo Nordisk outside the submitted work; Steindorf reported personal fees from Preventon and the Swiss Group for Clinical Cancer Research outside the submitted work; Schulze reported grants from the German Federal Ministry of Education and Research, the German Cancer Aid, and the State of Brandenburg (82DZD00302) during the conduct of the study.
Redberg reports grants from Arnold Ventures, the Greenwall Foundation, and the National Heart, Lung, and Blood Institute outside the submitted work.
Cat ID: 12
Topic ID: 76,12,730,102,446,12,13,669,918
