Chronic life stress, cardiovascular reactivity,

1
Chronic life stress, cardiovascular reactivity,
subclinical cardiovascular disease in adolescents

• Carissa A. Low, Kristen Salomon, Karen A.
  Matthews
• WPIC Research Day
• June 2009

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Cardiovascular health of adolescents

• Atherosclerosis begins in childhood
• Noninvasive imaging techniques permit examination
  of subclinical atherosclerosis in healthy
  adolescents

3
Chronic stress andcardiovascular disease (CVD)

• Chronic psychological stress is a risk factor for
  CVD in some but not all studies
• Studies that assess stress only once may not
  adequately capture chronic stress

4
Acute stress reactivity and CVD

• Cardiovascular reactivity to acute stress
  implicated as a mechanism linking psychological
  stress to CVD
• Most studies include a single assessment of
  cardiovascular reactivity, and changes in
  reactivity rarely examined

5
Whats missing

• Studies that include repeated assessments of
  chronic stress or cardiovascular reactivity, to
  examine the effects of increasing stress or
  reactivity on CVD
• Studies that examine the relationships between
  chronic stress, acute reactivity, and clinically
  significant markers of CVD in adolescents, a
  stage of profound developmental change

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Goal of current study

• To examine the association between increasing
  chronic life stress, increasing cardiovascular
  reactivity to laboratory stressors, and a marker
  of subclinical atherosclerosis in a sample of
  healthy adolescents

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Hypotheses

• Increasing chronic life stress will be associated
  with increasing cardiovascular reactivity
• Increasing chronic life stress will be associated
  with IMT
• Increasing cardiovascular reactivity will be
  associated with IMT

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Sample

• 158 healthy adolescents age 14-16 at study entry
• Recruited from two racially and socioeconomically
  diverse high schools
• 50 Black and 50 White
• 51 Female

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Study Design

• Time 1 (14 16 years old)
• Acute heart rate and blood pressure reactivity to
  mental arithmetic and mirror tracing
• Chronic life stress
• Time 2 ( 3.3 years later)
• Acute heart rate and blood pressure reactivity to
  mental arithmetic and mirror tracing
• Chronic life stress
• Subclinical atherosclerosis

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Measures

• Blood pressure and heart rate reactivity
• Change score Mean BP/HR during task mean
  BP/HR during initial rest (averaged across the
  two tasks)
• Life Events Questionnaire Adolescents
• Number of chronic, negative, independent events
  that happened in the past year

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LEQ Adolescents

• There were many arguments between adults living
  in the house.
• There were many family arguments with relatives.
• A family member developed severe emotional
  problems.
• A parent had problems at work.
• The family financial situation was difficult.

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Measures

• Blood pressure and heart rate reactivity
• Change score Mean BP/HR during task mean
  BP/HR during initial rest (averaged across the
  two tasks)
• Life Events Questionnaire Adolescents
• Number of chronic, negative, independent events
  that happened in the past year
• Subclinical atherosclerosis
• B-mode ultrasound to measure carotid intima-media
  thickness (IMT)

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Carotid Atherosclerosis

• IMT average thickness from the near and
  far walls of the common carotid artery and far
  walls of the bulb and internal carotid artery

Image source www.sti.nasa.gov
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Analytic plan

• Hierarchical linear regression
• Step 1 Covariates
• Age
• Sex
• Race
• BMI
• Time to follow-up
• Smoking status
• Baseline BP/HR where appropriate
• Step 2 Increasing stress / reactivity
• Time 2 Time 1

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Descriptive statistics
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Hypothesis 1 Stress reactivity

• Increasing chronic stress from Time 1 to Time 2
  was associated with increasing DBP reactivity
  (ß.20, p lt .01, ?R2 .04)

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Hypothesis 2 Stress IMT

• Increasing chronic stress was not associated with
  IMT (ß -.02, p gt .05)

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Hypothesis 3 Reactivity, IMT

• Increasing DBP reactivity from Time 1 to Time 2
  was associated with greater IMT (ß.26, p lt .05,
  ?R2 .03)

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Additional analyses

• Concurrent life stress
• T2 stress correlated with T2 DBP reactivity, but
  neither associated with IMT
• Cumulative life stress (Time 1 Time 2)
• No effect of cumulative life stress on reactivity
  or IMT
• Potential confounds
• Results unchanged when trait anxiety, depressive
  symptoms, social support, socioeconomic status
  were controlled

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Conclusions

• Exposure to increasing chronic stress during
  adolescence is accompanied by increases in
  cardiovascular stress reactivity.
• Increased diastolic blood pressure reactivity to
  acute stress is associated with greater IMT in
  healthy adolescents, even after adjustment for
  other risk factors.
• Chronic stress during adolescence was not
  associated with IMT.

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• Limitations
• Single assessment of IMT
• Healthy sample with restricted range for IMT
• Strengths
• Repeated assessments of chronic life stress
  cardiovascular reactivity
• Diverse adolescent sample
• Validated marker of vascular thickness

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Implications

• Adolescents exposed to chronic, worsening stress
  or those who are physiologically reactive to
  acute stress may be at risk for future CVD and
  represent an important target for early
  prevention efforts.
• Need to consider pattern of stress exposure and
  acute cardiovascular reactivity over time.

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Acknowledgements

• NIH grants (HL07560, HL25767, HL076852) to Karen
  Matthews
• John D. Catherine T. MacArthur Foundation
  Research Network on Socioeconomic Status
• NIH training grant (MH018269) to Paul Pilkonis