Projecting the Effect of Changes in Smoking and Obesity on Future Life

Expectancy in the United States

Samuel H. PrestonUniversity of Pennsylvania

Retirement Research Consortium ConferenceWashington, D.C.August 2, 2012

In Collaboration with Andrew Stokes and Bochen Cao, University of Pennsylvania and Neil Mehta, Emory

University

Figure 1. Trends in Smoking and Obesity in the United States

Sources: Cigarette consumption data per adult per year are extracted from Tobacco Situation and Outlook Report Yearbook. U.S. Department of Agriculture, October 2007. Obesity data based on measured body mass index in NHANES from 1960 to 2010.

Contrasting the Dynamics of Smoking and Obesity in the United States

Prevalence

Duration of Habit

Associated Mortality

Risk

Smoking

Obesity

Table 1A. Transition Probabilities across Categories of Body Mass Index, US Adults Ages 25-84, 1998-2008

  BMI in 2008

BMI in 1998 Normal Over Obese 1 Obese 2

Normal 0.63 0.33 0.03 0.01

Overweight 0.09 0.51 0.31 0.09

Obese Class 1 0.02 0.21 0.42 0.35

Obese Class 2 0.00 0.06 0.24 0.70

Table 1B. Differences in Transition Probabilities (Standard Errors) between 1980-1990 and 1990-2000, US Adults Ages 25-84

BMI in later year

BMI in early year Normal Over Obese 1 Obese 2

Normal -0.057* (0.019)

0.044* (0.016)

0.011* (0.004)

0.002* (0.001)

Overweight -0.012 (0.011)

-0.040* (0.017)

0.030 (0.015)

0.022* (0.010)

Obese Class 1 -0.006 (0.004)

-0.061* (0.023)

-0.033 (0.019)

0.100* (0.035)

Obese Class 2 -0.002 (0.001)

-0.026* (0.013)

-0.089* (0.035)

0.117* (0.047)

* p<0.05

Table 1C. Differences in Transition Probabilities (Standard Errors) between 1990-2000 and 2000-2010, US Adults Ages 25-84

BMI in later year

BMI in early year Normal Over Obese 1 Obese 2

Normal 0.022 (0.020)

-0.011 (0.017)

-0.009* (0.005)

-0.001 (0.001)

Overweight -0.010 (0.013)

0.029 (0.022)

-0.014 (0.021)

-0.004 (0.014)

Obese Class 1 0.003 (0.004)

0.046 (0.024)

0.010 (0.022)

-0.059 (0.031)

Obese Class 2 0.001 (0.001)

0.015 (0.014)

0.041 (0.039)

-0.056 (0.053)

* p<0.05

Figure 2A. Actual and Projected Trends in Body Mass Index (Males)

Figure 2B. Actual and Projected Trends in Body Mass Index (Females)

Data and Methods for the Analysis of the Mortality Risks of Obesity

Data: Baseline data are obtained by pooling NHANES 3 (1988-1994) and NHANES continuous waves 1999-2004. Mortality data are obtained from the National Death Index. Sample size: 21,554 respondents and 2,976 deathsMethod: Discrete hazards model, controlling for sex, race/ethnicity, educational attainment and smoking

Baseline Model Parameters for Regression Equation Predicting Mortality as a Function of Current Obesity and Obesity at Age 25

Covariates Coefficients SE t P>t

Female -0.309 0.050 -6.13 0.000

Age 0.099 0.004 25.58 0.000

Age 25

Overweight (BMI 25-30) 0.131 0.063 2.06 0.043

Obese (BMI>30) 0.309 0.106 2.91 0.005

Baseline

Obese class 1 (BMI 30-35) 0.355 0.339 1.05 0.299

Obese class 2 (BMI>35) 0.897 0.282 3.18 0.002

Obese class 1 x Age -0.008 0.009 -0.87 0.385

Obese class 2 x Age -0.018 0.008 -2.08 0.040

Constant -9.994 0.186 -53.79 0.000

Figure 3A. Effect of Projected Trends in Body Mass Index on Age-Specific Death Rates (Males)

40 45 50 55 60 65 70 75 80 850.80

0.85

0.90

0.95

1.00

1.05

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1.15

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2040

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40 45 50 55 60 65 70 75 80 850.80

0.85

0.90

0.95

1.00

1.05

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1.25

1.30

2020

2030

2040

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Figure 3B. Effect of Projected Trends in Body Mass Index on Age-Specific Death Rates (Females)

Table 5B. Changes in Life Expectancy at Age 40 Resulting from Changes in Obesity

Year Males Females

2020 -0.241 -0.174

2030 -0.467 -0.391

2040 -0.733 -0.677

Figure 4. Trends in Smoking and Lung Cancer Mortality in the United States

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Daily cigarettes per adultLung Cancer Mortality

Ciga

rett

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ay

Mor

talit

y ra

te (p

er 1

,000

)

Sources: Cigarette consumption data: International Smoking Statistics (2011); Lung cancer mortality data: National Center for Health Statistics.

Figure 5. U.S. Male Lung Cancer Mortality by Cohorts

Figure 6. U.S. Male Lung Cancer Mortality by Period

Equation for Projecting the Mortality Effects of Smoking

𝑙𝑛𝑀 (𝑎 ,𝑐 )=𝐴+𝐵𝛼 𝑋𝛼+𝐵𝑠 𝑙𝑛𝑆(𝑎 ,𝑐)Where,

• is the death rate at age a in cohort c• is the mean cumulative number of years smoked prior to age

40 for cohort c at age a• is an indicator of age category a• is the coefficient of age category a• is the coefficient of

Figure 7. Mean Number of Years Spent as a Cigarette Smoker before Age 40 by Cohort

40 45 50 55 60 65 70 75 80 850.75

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

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2030

2040

Age

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Figure 9A: Effect of Projected Trends in Smoking on Age-Specific Death Rates (Males)

Figure 9B: Effect of Projected Trends in Smoking on Age-Specific Death Rates (Females)

40 45 50 55 60 65 70 75 80 850.75

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

2020

2030

2040

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Table 5A. Changes in Life Expectancy at Age 40 Resulting from Changes in Smoking

Year Males Females

2015 0.281 -0.012

2020 0.576 0.089

2025 0.865 0.245

2030 1.115 0.477

2035 1.387 0.858

2040 1.617 1.142

40 45 50 55 60 65 70 75 80 850.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

2020

2030

2040

Age

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Figure 10A. Effect of Projected Trends in Smoking and Body Mass Index on Age-Specific Death Rates (Males)

40 45 50 55 60 65 70 75 80 850.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

1.30

2020

2030

2040

Age

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Figure 10B. Effect of Projected Trends in Smoking and Body Mass Index on Age-Specific Death Rates (Females)

Table 5C. Changes in Life Expectancy at Age 40 Resulting from Changes in Smoking and Obesity

 Changes in

Smoking Alone 

Changes in Obesity Alone

 Changes in

Smoking and Obesity

Year Males Females Males Females Males Females

2015 0.281 -0.012

2020 0.576 0.089 -0.241 -0.174 0.338 -0.076

2025 0.865 0.245

2030 1.115 0.477 -0.467 -0.391 0.662 0.117

2035 1.387 0.858

2040 1.617 1.142   -0.733 -0.677   0.914 0.539

Projected Changes in Life Expectancy at Age 40, 2010-2040

  Males Females

SSA projected increase* 2.55 2.17

Gain from reduced smoking 1.62 1.14

Penalty from higher obesity -0.73 -0.68

*Source: Felicitie C.Bell and Michael L. Miller. 2005. Life Tables for the United States Social Security Area 1900-2100. Social Security Administration Actuarial Study No. 120. Washington, D.C.

Table 6. Sensitivity of Results to Changes in Procedures

Change in Procedure Effect on Life Expectancy at age 40 Relative to Main Projection

2020 2030 2040Male Female Male Female Male Female

Use of mortality rates with no control except age & sex 0.016 0.009 0.023 0.018 0.029 0.031

Use of mortality rates without inclusion of BMI at age 25

0.029 0.012 0.131 0.082 0.293 0.198

Use of uncorrected data on obesity at age 25 -0.024 -0.026 -0.005 -0.036 0.044 -0.002

Use of alternative series translating lung cancer into all-cause mortality

-0.069 0.000   -0.178 -0.159   -0.330 -0.474