Body Mass Index, Weight Change and Death in an Older Hypertensive Population: The SHEP Study

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Body Mass Index, Weight Change and Death in an
Older Hypertensive Population The SHEP Study

• Grant W Somes
• Stephen B Kritchevsky
• Marco Pahor
• Ronald I Shorr
• William B Applegate
• University of Tennessee Health Science Center,
  Memphis, TN

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Background Static Measures of Weight and
Mortality

• In older populations, most studies show that low
  BMI is associated with increased mortality risk
• Fewer studies have shown that high BMI is
  associated with increased mortality risk
• The relationship with low BMI is attenuated in
  those with long-term weight stability,
  non-smokers, and those without weight related
  health conditions (Diehr et al., 1999 Calle et
  al., 1999).

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Background Dynamic Measures of Weight and
Mortality

• On a population-level, there is a general
  tendency for adults to lose weight after age 60.
  The dynamics of this change may be intimately
  related to health status.
• In clinical settings, acute weight loss
  (5/year) is associated with increased
  mortality.
• Most previous studies in older populations have
  had only two weights, one of which is recalled
  from over a decade previously.
• There is little data on older populations,
  looking at the importance of short-term weight
  change and mortality risk

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Study Questions In older adults...

• What is the relationship between baseline BMI and
  mortality?
• Outside of a clinical setting is weight change
  associated with mortality?
• What are the simultaneous effects of static and
  dynamic measures of weight on mortality?

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Systolic Hypertension in the Elderly Program
(SHEP)

• Randomized clinical trial of 4736 (isolated
  systolic) hypertensives, age 60 and older,
  comparing drug treatment with placebo.
• Primary endpoint was stroke (fatal or non-fatal).
• Vital status known for nearly 100 of enrolled
  subjects. (n455 deaths)
• Average duration of follow-up of 4.5 years.

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Present Study

• Inclusion Criteria
• 3 weight values
• 1 year follow-up beyond 3rd weight value
• Exclusion Criteria
• Missing data related to BMI calculation at
  baseline (randomization visit).
• Missing data related to covariates (eg. Gender,
  smoking, diabetes, prevalent CHD etc)
• 4485/4736 subjects were included
• 351 (7.83) deaths

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Methods

• BMI represents the BMI recorded at randomization
  visit (kg/m2).
• Weight measured quarterly, and at other SHEP
  visits.
• Weight change is the average annualized weight
  change based on the regression of weight on time
  from baseline until one year before last
  measurement (death, loss to follow-up, or end of
  study).
• Other baseline variables are gender, age (divided
  at 70), current smoking status, and risks
  (previous heart attack, stroke or diabetes)

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Analytic Strategy

• The primary outcome was all cause mortality.
• BMI and Weight Change were divided into quintiles
• Logistic regression was used to related mortality
  risk to weight change and baseline BMI compared
  to participants at lowest risk (23.6 to 28.0 BMI
  and -0.7 to 0.5 kg/year Weight Change)
• Covariates
• Age
• Gender
• Baseline smoking status
• Risk
• Prevalent CVD
• Diabetes

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Distribution of Risk Factors and Mortality in
SHEP (n 4485 )
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Distribution of time to event in SHEP
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Baseline BMI and Mortality
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Weight Change and Mortality
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BMI, Weight Change and Death1 year (n 351)
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BMI, Weight Change and Death 2 years (n281)
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Weight Change and Death, Baseline BMI 31.1
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Weight Change and Death, Baseline BMI 17
Weight Change in BMI Groups
BMI 31.1
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Weight Change and Mortalityby smoking status
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Weight Change and Mortalityby risk group
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Weight Change and Cancer (n135) or CVD (n148)
mortality
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Baseline BMI and Cancer (n135) or CVD (n148)
mortality
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Multivariate Model
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Discussion

• Weight loss of more than 0.7 kg/year was
  associated with high mortality risk--even in
  persons with high BMI.
• Weight gain of more than 0.5 kg/year was
  associated with high mortality risk--even in
  persons with low BMI.
• Findings consistent with 1-year and 2-year lag.
  Therefore observed relationship between weight
  change and mortality less likely to be ascribed
  to terminal illness.
• Our findings consistent across major causes of
  death.

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Conclusions

• Limitations
• Setting Clinical trial in Isolated Systolic
  Hypertension
• Involuntary v. voluntary weight change
• Dynamic weight measures are a more important
  predictor of mortality than static weight
  measures.
• Weight stability regardless of BMI is associated
  low mortality in older adults.