The impact of obesity on US mortality levels: the importance of age and cohort factors in population estimates

Abstract

Objectives: To estimate the percentage of excess death for US Black and White men and women associated with high body mass, we examined the combined effects of age variation in the obesity-mortality relationship and cohort variation in age-specific obesity prevalence.

Methods: We examined 19 National Health Interview Survey waves linked to individual National Death Index mortality records, 1986-2006, for age and cohort patterns in the population-level association between obesity and US adult mortality.

Results: The estimated percentage of adult deaths between 1986 and 2006 associated with overweight and obesity was 5.0% and 15.6% for Black and White men, and 26.8% and 21.7% for Black and White women, respectively. We found a substantially stronger association than previous research between obesity and mortality risk at older ages, and an increasing percentage of mortality attributable to obesity across birth cohorts.

Conclusions: Previous research has likely underestimated obesity's impact on US mortality. Methods attentive to cohort variation in obesity prevalence and age variation in obesity's effect on mortality risk suggest that obesity significantly shapes US mortality levels, placing it at the forefront of concern for public health action.

FIGURE 1—

Age-specific obesity rates by cohort among (a) White women, (b) Black women, (c) White men, and (d) Black men: National Health Interview Survey Linked Mortality Files, 1986–2004. Note. Obesity defined as body mass index ≥ 30 kg/m². Black horizontal line indicates average obesity rate for each subpopulation. Estimated from sample aged ≥ 25 years at the time of the survey.

FIGURE 2—

Fitted mortality hazard ratios by body mass index level, race/ethnicity, and sex for (a) White women, (b) Black women, (c) White men, (d) and Black men: National Health Interview Survey Linked Mortality Files, 1986–2004. Note. Overweight defined as body mass index 25.0–29.9 kg/m², grade 1 obesity as 30–34.9 kg/m², and grade 2/3 obesity as ≥ 35 kg/m².

FIGURE 3—

Grade 1 obesity–attributable mortality by age, cohort, race/ethnicity, and sex for (a) White women, (b) Black women, (c) White men, (d) and Black men: National Health Interview Survey Linked Mortality Files, 1986–2004. Note. PAF = population attributable fraction. Grade 1 obesity defined as body mass index 30–34.9 kg/m².