Heart disease and stroke: Down, but not out

In this Issue, Shah and colleagues estimated the trends in the incidence and outcomes of myocardial infarction and stroke in Scotland from 1990 to 2014. Age-standardized incidence fell by 75% and 70%, respectively, and at least two-thirds of the decline can be attributed to decrease in three risk factors: systolic blood pressure, smoking and blood cholesterol [1]. However, Shah and colleagues also observed a doubling in the prevalence of diabetes associated with an increase in body mass index (BMI) to the extent that somewhat more than one quarter of the population was obese (BMI 30 kg/m² or greater) by 2016. Estimating that the increase in these two risk factors contributed to as many incident myocardial infarctions as were prevented by the reduction in smoking during the same period, they advised that, “Public health efforts now need to urgently focus on managing obesity and diabetes to further curb cardiovascular disease.”

The rise in the prevalence of diabetes and obesity is particularly ominous because all of the developed economies are experiencing it, and no concrete health policy has stopped or prevented the rising number of cases despite the attention from various institutions. Obesity and related aspects of nutrition and physical activity policy have been the topic of more than 40 Institute of Medicine (IOM, now the National Academy of Medicine) consensus studies and workshops since 2004 [2], and the World Health Organization has recommended actions to prevent childhood obesity [3].

Two observations in particular suggest that the return of coronary heart disease and stroke secondary to obesity will be particularly difficult to prevent: While weight reduction of only 5-10% of body weight is known to reduce risk of death, diabetes, and several other diseases [4], maintained weight loss of even this magnitude is rare in adulthood. Likewise, randomized trial evidence that diabetes can be prevented[5] has not stopped the increase in diabetes prevalence in either Europe or the United States.

Cited by Shah and colleagues, Kumanyika and Dietz[2] advise that the obesity epidemic can only be overcome by restructuring the food, transportation, housing, education, and community planning sectors. The Lancet Commission on Obesity advocates for confronting obesity as a “syndemic”—the co-occurrence of the pandemics of obesity, undernutrition and climate change that interact with each other to amplify the harm they cause [6]. Similar to the observations of Kumanyika and Dietz [2], the Lancet Commission recommends policy changes in the food, transport, urban design, and land use systems. The Lancet Commission policy brief lists 18 “double-duty and triple-duty actions” that can be taken by all: nations and municipalities; civil society; funders; and, international agencies.

The inability to significantly reduce obesity in adults at a population level suggests that interventions that prevent child and adolescent obesity need to be developed and implemented. Rather than focusing on the weight of individual children, evidence-informed programs, policies, and systems should be used to create environments that promote healthy nutrition and physical activity [7]. Focusing on individual children only stigmatizes without having the intended effect of obesity prevention [8]. By contrast, policy that improves the foods served in schools has been observed to reduce obesity trends in children at highest risk [9]. As just one part of a wholistic strategy, creating health-promoting environments that benefit multigenerational families as they benefit children and youth may also help adults avoid the weight gains that they are likely to experience in their 20’s and 30’s. Weight gain in early adulthood remains an unresolved problem.

Shah and colleagues acknowledged several limitations to their analysis, all of which must be considered. For example, when they estimated the potential impact of risk factors, they assumed that each risk factor is mutually exclusive. Risk factors do not occur in isolation; thus, the impact of a single risk factor is likely to be overestimated. They have also not considered lag time for risk factor effect; while the effect of smoking is nearly immediate, the effects of diabetes and obesity are probably manifested only after many years. Finally, because the population of Scotland is predominantly white, their findings might not apply in other regions of the world. But none of these limitations negate their conclusion that public health efforts are needed now to urgently focus on managing obesity and diabetes to further curb cardiovascular disease. These efforts will require both personal commitment and innovative science-based policies to create physical and social environments that promote cardiovascular health. What is not known is whether the world will mobilize in the 21^st Century to confront the obesity epidemic as it did for heart disease and stroke in the 20^th.

Authors Contributors

Dr. Kottke was the primary author of the commentary. Marna Canterbury contributed background and advice about the content.

Declaration of Interests

Dr. Kottke has nothing to disclose. Ms. Canterbury has nothing to disclose.