Body Mass Index, Diabetes, Hypertension, and Short-Term Mortality: A Population-Based Observational Study, 2000-2006
ABSTRACT Published studies about the association of obesity with mortality have used body mass index (BMI) data collected more than 10 years ago, potentially limiting their current applicability, particularly given evidence of a secular decline in obesity-related mortality. The objective of this study was to examine the association between BMI and mortality in a representative, contemporary United States sample.
This was a population-based observational study of data from 50,994 adults aged 18 to 90 years who responded to the 2000 to 2005 Medical Expenditures Panel Surveys. Cox regression analyses were employed to model survival during up to 6 years of follow-up (ascertained via National Death Index linkage) by self-reported BMI category (underweight, <20 kg/m(2); normal weight, 20-<25 [reference]; overweight, 25-<30; obese, 30-<35; severely obese, ≥35), without and with adjustment for diabetes and hypertension. Survival by BMI category also was modeled for diabetic and hypertensive individuals. All models were adjusted for sociodemographics, smoking, and Medical Expenditures Panel Surveys response year.
In analyses not adjusted for diabetes or hypertension, only severe obesity was associated with mortality (adjusted hazard ratio, 1.26; 95% confidence interval, 1.00-1.59). After adjusting for diabetes and hypertension, severe obesity was no longer associated with mortality, and milder obesity (BMI 30-<35) was associated with decreased mortality (adjusted hazard ratio, 0.81; 95% confidence interval, 0.68-0.97). There was a significant interaction between diabetes (but not hypertension) and BMI (F [4, 235] = 2.71; P = .03), such that the mortality risk of diabetes was lower among mildly and severely obese persons than among those in lower BMI categories.
Obesity-associated mortality risk was lower than estimated in studies employing older BMI data. Only severe obesity (but not milder obesity or overweight) was associated with increased mortality, an association accounted for by coexisting diabetes and hypertension. Mortality in diabetes was lower among obese versus normal weight individuals.
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ABSTRACT: We present three considerations in analysing the association between weight and mortality, as well as other relations that might be non-linear in nature. First, authors must graphically plot their independent and dependent variables in a continuous manner. Second, authors should assess the shape of that relation, and note its shape. If it is non-linear, and specifically, J-shaped or U-shaped, careful consideration should be given to using the 'best' statistical model, of which multivariate fractional polynomial regression is a reasonable choice. Authors should also refrain from truncating their data to avoid dealing with non-linear relations.Journal of epidemiology and community health 03/2014; 68(7). DOI:10.1136/jech-2013-203439 · 3.29 Impact Factor
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ABSTRACT: While many studies have examined differences between body mass index (BMI) categories in terms of mortality risk and health-related quality of life (HRQL), little is known about the effect of body weight on health expectancy. We examined life expectancy (LE), health-adjusted life expectancy (HALE), and proportion of LE spent in nonoptimal (or poor) health by BMI category for the Canadian adult population (age >= 20). Respondents to the National Population Health Survey (NPHS) were followed for mortality outcomes from 1994 to 2009. Our study population at baseline (n=12,478) was 20 to 100 years old with an average age of 47. LE was produced by building abridged life tables by sex and BMI category using data from the NPHS and the Canadian Chronic Disease Surveillance System. HALE was estimated using the Health Utilities Index from the Canadian Community Health Survey as a measure of HRQL. The contribution of HRQL to loss of healthy life years for each BMI category was also assessed using two methods: by calculating differences between LE and HALE proportional to LE and by using a decomposition technique to separate out mortality and HRQL contributions to loss of HALE. At age 20, for both sexes, LE is significantly lower in the underweight and obesity class 2+ categories, but significantly higher in the overweight category when compared to normal weight (obesity class 1 was nonsignificant). HALE at age 20 follows these same associations and is significantly lower for class 1 obesity in women. Proportion of life spent in nonoptimal health and decomposition of HALE demonstrate progressively higher losses of healthy life associated with lowered HRQL for BMI categories in excess of normal weight. Although being in the overweight category for adults may be associated with a gain in life expectancy as compared to normal weight adults, overweight individuals also experience a higher proportion of these years of life in poorer health. Due to the descriptive nature of this study, further research is needed to explore the causal mechanisms which explain these results, including the important differences we observed between sexes and within obesity subcategories.Population Health Metrics 11/2013; 11(1):21. DOI:10.1186/1478-7954-11-21 · 2.11 Impact Factor
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ABSTRACT: Class I obesity conveys an increased risk of comorbidities, impairs physical and mental health-related quality of life, and it is associated to an increased psychosocial burden, particularly in women. The need for effective and safe therapies for class I obesity is great and not yet met by nonsurgical approaches. Eligibility to bariatric surgery has been largely based on body mass index (BMI) cut points and limited to patients with more severe obesity levels. However, obese patients belonging to the same BMI class may have very different levels of health, risk, and impact of obesity on quality of life. Individual patients in class I obesity may have a comorbidity burden similar to, or greater than, patients with more severe obesity. Therefore, the denial of bariatric surgery to a patient with class I obesity suffering from a significant obesity-related health burden and not achieving weight control with nonsurgical therapy simply on the basis of the BMI level does not appear to be clinically justified. A clinical decision should be based on a more comprehensive evaluation of the patient's current global health and on a more reliable prediction of future morbidity and mortality. After a careful review of available data about safety and efficacy of bariatric surgery in patients with class I obesity, this panel reached a consensus on ten clinical recommendations.Obesity Surgery 03/2014; DOI:10.1007/s11695-014-1214-1 · 3.74 Impact Factor