Deaths associated with obesity may be declining in the United States
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《英国医生杂志》
Being obese or underweight is associated with increased mortality, but the number of deaths associated with obesity appears to be decreasing over time, possibly due to improved management of other cardiovascular risk factors, according to survey data from the United States published this week ( JAMA 2005;293: 1861-7).
The researchers looked at the relative risks of mortality associated with different levels of body mass index (BMI) from the nationally representative National Health and Nutrition Examination Survey (NHANES 1971-5) and NHANES II (1976-80), with follow-up to 1992, and from NHANES III (1988-94), with follow-up to 2000.
The results showed that obesity (BMI30) was associated with 111 909 (95% confidence interval 53 754 to 170 064) excess deaths in the year 2000 and underweight (BMI<18.5) with 33 746 (15 726 to 51 766) excess deaths compared with people of normal weight (18.5BMI<25). Overweight (25BMI<30) was not associated with excess mortality.
Looking at trends over time, the relative risks of mortality associated with obesity were lower in more recent data from NHANES II and NHANES III than in NHANES I. Katherine Flegal, senior research scientist at the National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland, and lead author of the study, said, "The differences between NHANES I and the later surveys suggest that the association of obesity with total mortality may have decreased over time, perhaps because of improvements in public health or medical care for obesity related conditions."
A second analysis of the NHANES data looking at 40 year trends in cardiovascular disease risk factors by BMI categories, showed that the prevalence of high cholesterol levels (>240 mg/dl), hypertension (>140/90 mm Hg), and current smoking had declined, particularly in people who were overweight or obese. Diabetes was the only risk factor that had remained stable in prevalence over the 40 years ( JAMA 2005;293: 1868-74).
Compared with obese people in the first NHANES data from 1960-2, the obese group in 1999-2000 had a 21% lower prevalence of high cholesterol level (39% in 1960-2 v 18% in 1999-2000), an 18% lower prevalence of high blood pressure (42% v 24%), and a 12% lower rate of smoking (32% v 20%). The prevalence of high cholesterol had fallen more in people who were obese and overweight than in those who were normal weight or below (P<0.05). Changes in risk factors were accompanied by increases in lipid lowering and antihypertensive drug use, particularly in obese people.
Total diabetes prevalence was stable within different BMI groups over time, with a non-significant 1%-2% increase between 1976-80 and 1999-2000. However, this was accompanied by a 55% increase in total diabetes among the overall population (all BMI groups combined).
The researchers said, "In this unique series of nationally representative surveys of the US adult population, we documented a substantial decline in the prevalence of key risk factors over the last three to four decades, affecting obese, overweight, and lean segments of the population."(Susan Mayor)
The researchers looked at the relative risks of mortality associated with different levels of body mass index (BMI) from the nationally representative National Health and Nutrition Examination Survey (NHANES 1971-5) and NHANES II (1976-80), with follow-up to 1992, and from NHANES III (1988-94), with follow-up to 2000.
The results showed that obesity (BMI30) was associated with 111 909 (95% confidence interval 53 754 to 170 064) excess deaths in the year 2000 and underweight (BMI<18.5) with 33 746 (15 726 to 51 766) excess deaths compared with people of normal weight (18.5BMI<25). Overweight (25BMI<30) was not associated with excess mortality.
Looking at trends over time, the relative risks of mortality associated with obesity were lower in more recent data from NHANES II and NHANES III than in NHANES I. Katherine Flegal, senior research scientist at the National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, Maryland, and lead author of the study, said, "The differences between NHANES I and the later surveys suggest that the association of obesity with total mortality may have decreased over time, perhaps because of improvements in public health or medical care for obesity related conditions."
A second analysis of the NHANES data looking at 40 year trends in cardiovascular disease risk factors by BMI categories, showed that the prevalence of high cholesterol levels (>240 mg/dl), hypertension (>140/90 mm Hg), and current smoking had declined, particularly in people who were overweight or obese. Diabetes was the only risk factor that had remained stable in prevalence over the 40 years ( JAMA 2005;293: 1868-74).
Compared with obese people in the first NHANES data from 1960-2, the obese group in 1999-2000 had a 21% lower prevalence of high cholesterol level (39% in 1960-2 v 18% in 1999-2000), an 18% lower prevalence of high blood pressure (42% v 24%), and a 12% lower rate of smoking (32% v 20%). The prevalence of high cholesterol had fallen more in people who were obese and overweight than in those who were normal weight or below (P<0.05). Changes in risk factors were accompanied by increases in lipid lowering and antihypertensive drug use, particularly in obese people.
Total diabetes prevalence was stable within different BMI groups over time, with a non-significant 1%-2% increase between 1976-80 and 1999-2000. However, this was accompanied by a 55% increase in total diabetes among the overall population (all BMI groups combined).
The researchers said, "In this unique series of nationally representative surveys of the US adult population, we documented a substantial decline in the prevalence of key risk factors over the last three to four decades, affecting obese, overweight, and lean segments of the population."(Susan Mayor)