Overweight and Mortality among Baby Boomers — Now We're Getting Personal
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《新英格兰医药杂志》
I am a baby boomer, and my body-mass index (BMI) is 27.3. I am also an epidemiologist, so for both personal and professional reasons, I have closely followed the sometimes divergent conclusions about the health risks associated with growing older and being a little overweight. As reported in this issue of the Journal, trials involving more than half a million Americans (Adams et al., pages 763–778) and more than a million Koreans (Jee et al., pages 779–787) are the latest in a series of cohort studies published in recent years on the risks associated with excess adiposity. Now that studies are beginning to describe the risk of death associated with even modest levels of adiposity among baby boomers, this issue is getting more personal for me.
At first glance, the new study involving members of the AARP (formerly the American Association of Retired Persons) looks reassuring for those of us who are not obese, but only overweight. Among the entire cohort of AARP members, the risk of death seems to be substantially increased only for those whose BMI is over 30, the cutoff defining obesity. However, we have learned in recent years that only studies of the relationship between adiposity and the risk of death that properly account for tobacco use and chronic medical conditions can be truly informative about the risk caused by lesser degrees of adiposity. The AARP study clearly shows that if the effects of smoking are set aside, at age 50, when the prevalence of chronic disease is low, there is also an elevated risk of death for persons whose BMIs are well below 30.
The study of adiposity and mortality among Korean adults also shows a graded relationship between BMI and death from atherosclerotic cardiovascular disease across a very wide range of BMI levels, including what would be regarded as only modest levels of adiposity in the United States. This finding is a sobering reminder that because obesity is now a worldwide problem, the phenomenon of "global fattening" will contribute to a pandemic of chronic diseases for many years to come.
What are we to do about the epidemic of adiposity, both collectively and personally? As health care providers, we are all touched by the personal dimensions of the problem, sometimes because we are ourselves overweight and sometimes because of the many personal issues that arise as we try to help our patients. The medical management of hypertension, hyperlipidemia, and insulin resistance certainly helps, but the treatment of these mediating factors does not completely eliminate the excess risk associated with adiposity. Adverse consequences of adiposity are seen in even quite health-conscious cohorts, such as AARP members, insured Korean patients, American Cancer Society volunteers, and registered nurses.1,2 Our inability to negate these health risks may be due to the irreversibility of some of the biologic harm, our inability to achieve perfect control over the known mediating factors, or the effects of other as-yet-uncontrollable factors, such as the chronic inflammatory state of adiposity, as is signaled by the association between white-cell counts and BMI in the Korean cohort study.
We baby boomers are now into the second half of our lives. How will our current excess weight, much of it gained after age 50 during the ongoing obesity epidemic, affect our health risks as we age? A 1999 study conducted in an American Cancer Society cohort of more than a million Americans1 provides a clear answer: among nonsmokers without chronic medical conditions, the risk of death is elevated even among the modestly overweight, and this elevated risk persists as age advances (see graph). Observations that the risk of death expressed as a ratio (including the relative risk in the AARP cohort and the hazard ratio in the Korean cohort) diminishes with advancing age cannot be taken as evidence that the effects of adiposity diminish. In fact, the absolute degree of additional risk associated with excess adiposity (the difference in risk between overweight persons and those of normal weight) substantially increases with advancing age, according to the analysis of the American Cancer Society cohort. Risk ratios diminish with advancing age simply because the ratios are diluted by the many other causes of death associated with aging, which figure into both the numerator and the denominator of the ratio.
Risk of Death Associated with BMI among Male Nonsmokers without Chronic Health Conditions, According to Age.
The annual risk of death is expressed as both the relative risk (Panel A) and the absolute amount of additional risk (risk difference) (Panel B) per 100,000 population, as reported in the American Cancer Society Cancer Prevention Study 2.1 Even though the excess risk of death due to adiposity increased with age, the relative risk decreased with age because of dilution by the many other causes of death associated with increasing age.
As we baby boomers move past 50, we will have to address the reality that excess adiposity substantially increases with advancing age. Fortunately, evidence points to a substantial health benefit from even small changes in weight trajectory, so the achievement of an ideal body weight need not be the primary goal. There are many ways that physicians can help patients to make the critical first step of stopping weight gain.3 Small steps toward weight control, such as short bursts of activity and discrete changes in eating habits, need not require major lifestyle modification.
In my own personal adiposity epidemic, small steps seem to help. When I turned 50, I began to gain weight, even though it seemed that my eating and activity habits had not changed. When I turned 55, I cut out powdered doughnuts and began to walk more. Now, at age 57, I am 10 pounds lighter, my wife is happier that there is less powdered sugar on the seat of the car, and I have a little more energy. As I reflect on my BMI of 27.3, however, I am now looking for more small steps. My office is located on the fourth floor of a building with both stairs and an elevator. Hmmm.
Source Information
Dr. Byers is a professor of preventive medicine at the University of Colorado School of Medicine, Denver.
References
Calle EE, Thun MJ, Petrelli JM, Rodriguez C, Heath CW Jr. Body-mass index and mortality in a prospective cohort of U.S. adults. N Engl J Med 1999;341:1097-1105.
Manson JE, Willett WC, Stampfer MJ, et al. Body weight and mortality among women. N Engl J Med 1995;333:677-685.
Manson JE, Skerrett PJ, Greenland P, VanItallie TB. The escalating pandemics of obesity and sedentary lifestyle: a call to action for clinicians. Arch Intern Med 2004;164:249-258.(Tim Byers, M.D., M.P.H.)
At first glance, the new study involving members of the AARP (formerly the American Association of Retired Persons) looks reassuring for those of us who are not obese, but only overweight. Among the entire cohort of AARP members, the risk of death seems to be substantially increased only for those whose BMI is over 30, the cutoff defining obesity. However, we have learned in recent years that only studies of the relationship between adiposity and the risk of death that properly account for tobacco use and chronic medical conditions can be truly informative about the risk caused by lesser degrees of adiposity. The AARP study clearly shows that if the effects of smoking are set aside, at age 50, when the prevalence of chronic disease is low, there is also an elevated risk of death for persons whose BMIs are well below 30.
The study of adiposity and mortality among Korean adults also shows a graded relationship between BMI and death from atherosclerotic cardiovascular disease across a very wide range of BMI levels, including what would be regarded as only modest levels of adiposity in the United States. This finding is a sobering reminder that because obesity is now a worldwide problem, the phenomenon of "global fattening" will contribute to a pandemic of chronic diseases for many years to come.
What are we to do about the epidemic of adiposity, both collectively and personally? As health care providers, we are all touched by the personal dimensions of the problem, sometimes because we are ourselves overweight and sometimes because of the many personal issues that arise as we try to help our patients. The medical management of hypertension, hyperlipidemia, and insulin resistance certainly helps, but the treatment of these mediating factors does not completely eliminate the excess risk associated with adiposity. Adverse consequences of adiposity are seen in even quite health-conscious cohorts, such as AARP members, insured Korean patients, American Cancer Society volunteers, and registered nurses.1,2 Our inability to negate these health risks may be due to the irreversibility of some of the biologic harm, our inability to achieve perfect control over the known mediating factors, or the effects of other as-yet-uncontrollable factors, such as the chronic inflammatory state of adiposity, as is signaled by the association between white-cell counts and BMI in the Korean cohort study.
We baby boomers are now into the second half of our lives. How will our current excess weight, much of it gained after age 50 during the ongoing obesity epidemic, affect our health risks as we age? A 1999 study conducted in an American Cancer Society cohort of more than a million Americans1 provides a clear answer: among nonsmokers without chronic medical conditions, the risk of death is elevated even among the modestly overweight, and this elevated risk persists as age advances (see graph). Observations that the risk of death expressed as a ratio (including the relative risk in the AARP cohort and the hazard ratio in the Korean cohort) diminishes with advancing age cannot be taken as evidence that the effects of adiposity diminish. In fact, the absolute degree of additional risk associated with excess adiposity (the difference in risk between overweight persons and those of normal weight) substantially increases with advancing age, according to the analysis of the American Cancer Society cohort. Risk ratios diminish with advancing age simply because the ratios are diluted by the many other causes of death associated with aging, which figure into both the numerator and the denominator of the ratio.
Risk of Death Associated with BMI among Male Nonsmokers without Chronic Health Conditions, According to Age.
The annual risk of death is expressed as both the relative risk (Panel A) and the absolute amount of additional risk (risk difference) (Panel B) per 100,000 population, as reported in the American Cancer Society Cancer Prevention Study 2.1 Even though the excess risk of death due to adiposity increased with age, the relative risk decreased with age because of dilution by the many other causes of death associated with increasing age.
As we baby boomers move past 50, we will have to address the reality that excess adiposity substantially increases with advancing age. Fortunately, evidence points to a substantial health benefit from even small changes in weight trajectory, so the achievement of an ideal body weight need not be the primary goal. There are many ways that physicians can help patients to make the critical first step of stopping weight gain.3 Small steps toward weight control, such as short bursts of activity and discrete changes in eating habits, need not require major lifestyle modification.
In my own personal adiposity epidemic, small steps seem to help. When I turned 50, I began to gain weight, even though it seemed that my eating and activity habits had not changed. When I turned 55, I cut out powdered doughnuts and began to walk more. Now, at age 57, I am 10 pounds lighter, my wife is happier that there is less powdered sugar on the seat of the car, and I have a little more energy. As I reflect on my BMI of 27.3, however, I am now looking for more small steps. My office is located on the fourth floor of a building with both stairs and an elevator. Hmmm.
Source Information
Dr. Byers is a professor of preventive medicine at the University of Colorado School of Medicine, Denver.
References
Calle EE, Thun MJ, Petrelli JM, Rodriguez C, Heath CW Jr. Body-mass index and mortality in a prospective cohort of U.S. adults. N Engl J Med 1999;341:1097-1105.
Manson JE, Willett WC, Stampfer MJ, et al. Body weight and mortality among women. N Engl J Med 1995;333:677-685.
Manson JE, Skerrett PJ, Greenland P, VanItallie TB. The escalating pandemics of obesity and sedentary lifestyle: a call to action for clinicians. Arch Intern Med 2004;164:249-258.(Tim Byers, M.D., M.P.H.)