Boston, MA - Two studies appearing in the December 6, 2007 issue of the New England Journal of Medicine provide new—and shocking—insights in the anticipated expansion of the heart-disease epidemic in years to come, given soaring rates of overweight and obesity in today's kids and adolescents . In one paper, Dr Jennifer L Baker (Institute of Preventive Medicine, Copenhagen, Denmark) and colleagues demonstrate in a huge retrospective cohort analysis that body-mass index (BMI) in childhood is significantly associated with fatal and/or nonfatal coronary heart disease in adults over age 25. In a second study, Dr Kirsten Bibbins-Domingo (University of California, San Francisco) and her coauthors report the results of a computer-generated model that suggests CHD prevalence in 2035 will be 5% to 16% higher than it is today, given current obesity rates among teens.
Deaths due to CHD will be even higher, up as much as 19% when today's teenagers reach age 35 to 50, she told heartwire. "To some extent our results are not unexpected. We would expect that there would be more heart disease and deaths, but we were struck really by the magnitude of this increase."
BMI in boys and girls; CHD in adults
We would expect that there would be more heart disease and deaths, but we were struck really by the magnitude of this increase.
Baker et al looked at rates of heart-disease events in more than 250 000 Danish citizens whose height and weight had been tracked as schoolchildren, yielding more than five million person-years of follow-up. They report that 10 235 men and 4318 women either died of CHD or received a diagnosis of CHD as adults and that these events were associated with a higher BMI during ages 7 to 13 for boys and ages 10 to 13 for girls.
"Our study is the largest of its kind and the first to convincingly demonstrate that excess childhood BMI increases the risk of heart disease in adulthood," Baker told heartwire.
As childhood BMI increased, so did the risk of heart disease in adulthood, the authors note. By way of example, Baker and colleagues estimated that a 13-year-old boy who weighs 11.2 kg more than average would increase his probability of having a CHD event before age 60 by 33%.
"We were very surprised by the linear nature of the association," Baker commented. "We had expected to find a threshold BMI value at which the risk increased dramatically or leveled off. Given that children are becoming heavier and heavier at progressively younger ages, our results suggest that far too many children from current generations are facing a future burdened with heart disease."
CHD risk associated with BMI also increased with age, Baker et al report. Whereas increased BMI was associated with a moderate risk of developing heart disease in adulthood, by age 13, that risk was even higher. "Taken together, these results suggest that even in this short period of childhood, interventions aimed at helping children attain and maintain an appropriate weight can protect them from future adverse health consequences," Baker told heartwire.
Computer model projects early, rampant CHD
Dr Kirsten Bibbins-Domingo (Source: University of California, San Francisco)
In the Bibbins-Domingo paper, authors used the prevalence of overweight in adolescents in 2000 (16.7% in boys and 15.4% in girls) as well as historical trends linking weight in adolescence to obesity prevalence in adulthood to create computer-generated projections for the prevalence of obesity in 2020, when these teens would be 35 years old. In their analysis, obesity prevalence among 35-year-olds in 2020 will increase to 30% to 37% in men and to 34% to 44% in women; obesity prevalence in adults of this age today is 25% and 32%, respectively. These increases will translate into a higher number of CHD events and deaths in young adulthood that will continue to rise in middle age, the authors predict. By 2035, Bibbins-Domingo et al calculated that there will be more than 100 000 excess cases of CHD attributable to increased obesity in the US alone.
The findings are particularly striking because the computer model did not forecast CHD events in older adults but in earlier adulthood not typically thought of as a time to worry about heart disease, Bibbins-Domingo pointed out to heartwire. "This is an age when people are not going to their doctors with high frequency. They are working, raising their families, and heart disease is something that we think about happening later. What we're saying is that we'll actually be seeing a shift in the pattern of heart disease, so that we start to see heart disease in this younger population as a consequence of these higher rates of overweight among today's adolescents."
Importantly, her paper looks only at the impact of overweight on future CHD: mounting research, including Baker et al's paper, suggests that overweight kids are likely also developing related CHD risk factors much earlier, and this possibility is not even factored into in Bibbins-Domingo et al's model.
"If we take that into consideration and we believe the emerging evidence, then it would suggest that our estimates are actually underestimates," she told heartwire. When her group plugged Baker et al's estimates into their model, the projected rates of CHD were even higher than those in the published paper. "There is emerging evidence that some of the fat itself and the distribution of fat may have an adverse effect over time on how the CHD processes develop in the heart, so there may even be some heart damage going on at these early stages," she said.
Many variables unknown
Bibbins-Domingo and her coauthors acknowledge that their model cannot account for everything, and one important factor might be the development of better preventive medicines or treatments for CHD risk factors such as hyperlipidemia, hypertension, diabetes, and even obesity itself.
"We don't know—there could be therapies in the future that might lower your likelihood of getting diabetes, for example, and that might actually dramatically reverse obesity, and we of course can't consider those in the model," she admitted. "What we can say, however, is that the magnitude of the effect of those interventions would have to be pretty great to be able to change these trends, and they would have to happen at a pretty early age. We would have to be able to treat young adults or adolescents with whatever these therapies are, which is, again, a shift from how we think about when to use medication."
Indeed, one of the strongest messages from both papers is that patients, physicians, and policy makers need to radically overhaul their preconceived notions about when to start prevention strategies and even treatments for CHD. Even the drugs used today to control hypertension and cholesterol have not been widely tested in younger patients, and there is little evidence to support the safety of taking some of these medications for what amounts to most of an adult's lifespan.
Bibbins-Domingo et al point out that their study also does not account for a changing US population due to immigration and shifting demographics, but she noted to heartwire that if anything, overweight and obesity rates are even higher in minority groups and that the disease projections in their model likely underestimate disease projections in specific ethnic groups, including African Americans, Latinos, and Native Americans.
Simple solutions, politics aside
Dr David S Ludwig (Source: Jason Grow)
In a Perspective accompanying the two studies , Dr David S Ludwig (Children's Hospital Boston, MA) describes what he terms the four overlapping phases of the obesity epidemic and describes the major barriers that need to be confronted if it is to be curtailed in any meaningful way. In an online interview accompanying his Perspective, he points out that while there's been increasing awareness of the childhood obesity problem, few people have been able to appreciate what its impact will be down the road.
"It's one thing for an overweight 45-year-old to develop type 2 diabetes at age 55 and suffer a stroke, a heart attack, or renal failure at age 65," he points out. "It's a very different thing if the clock starts ticking at age 10."
He likens the problem to global warming: the childhood obesity epidemic, he writes, "is a looming crisis that requires action before all the scientific evidence is in." But unlike global warming, there are relatively simple solutions to the childhood obesity problem, as long as the strategy is comprehensive, with the full backing of public-policy initiatives.
"We have every reason to believe that simple, albeit politically difficult, initiatives can begin to curtail the increase in prevalence rate and then ultimate lower prevalence rate," Ludwig states in the online audio interview.