Post on 30-Dec-2015
description
“A meta-analysis of the effectiveness of health
belief model variables in predicting behavior”
Carpenter, 2010
Natalie LintonOregon State UniversityOctober 9, 2014
What is the Health Beliefs Model (HBM)?
Developed by the U.S. Public Health Service in the 1950s
Based in value-expectancy theory
http://xkcd.com/51/
measles
What is a meta-analysis?
Statistical methods for contrasting and combining results from different studies
Meta-analyses can identify: patterns sources of
disagreement
Previous HBM meta-analyses:
Janz & Becker 1984 barriers, benefits, susceptibility did not estimate mean effect sizes
Harrison et. al. 1992 retrospective studies = larger
effect sizes than prospective did not correct effect size
estimates
Zimmerman & Vernberg 1994 HBM prediction weak compared to
Social Cognitive Theory and TRA did not examine the effects of
each variable on behavior
Why did Carpenter conduct a meta-analysis of the HBM?
Determine whether measures of HBM concepts could longitudinally predict behavior
Which elements are strong predictors?
What are the moderators?
Moderators found: Time between variable measurement
(Time 1) and outcome behavior measurement (Time 2)
Type of outcome behavior:Prevention or treatmentDrug-taking or not drug-related
Methodology
18 studies (2,702 subjects); published 1982-2007
Looked at only the first 4 concepts of HBM:Susceptibility (18), severity (17), barriers (17), benefits
(15)Studies had to include at least 2 of the 4
Studies had to be longitudinalTime 1: measure HBM variablesTime 2: measure health-related behavior outcome
Outcome dichotomized as treatment (8 studies) or prevention behavior (10 studies)
Outcome also dichotomized as drug-taking behavior (5 studies) or other behavior (13 studies)
Perceived susceptibility
Usually not correlated with health behavior (weakest predictor)
Estimates mostly homogenous
Subset of drug-taking studies only set for which susceptibility was positively correlated with behavior
Moderator: length of timeLonger periods of time between Time 1 and Time 2
associated with weaker effectsr = -0.50
Perceived severity“There is something about about considering
complying with a prescription to take drugs that causes people to consider the severity of the consequences for not taking the drugs more so than for other health behaviors”
Moderator: length of timeSeverity ratings more likely to be positively
correlated to behavior if the behavior is measured shortly after Time 1
r = -0.37
Perceived benefits and barriers
Strongest predictors of behaviorsStronger when dealing with
preventive behavior
Findings mostly consistent with previous literature
Moderator for perceived benefits: length of timeLonger periods of time
between Time 1 and Time 2 associated with weaker effects r = -0.59
http://xkcd.com/388/
Limitations
Small number of studies
Not enough articles providing effect sizes
Variety and varying quality of measures used
16 (of 18) articles relied on convenience samples
Did not test more complex models that are possible and would be better to test (studies would have needed to report full correlation matrices)
DECISIONS/INTENTIONS
SOCIAL SITUATION
BIOLOGY/PERSONALITY
ATTITUDESTOWARD THE
BEHAVIOR
SOCIALNORMATIVE
BELIEFS
Trial Behavior
EXPERIENCES: Expectancies -- Social Reinforcements -- Psychological/Physiological
SELF-EFFICACYBEHAVIORAL
CONTROL
Nurture/CulturalBiological/NatureIntrapersonal Stream Social/Normative Stream Cultural/Attitudinal Stream
Values/Evaluations
Knowledge/Expectancies
PerceivedNorms
Information/Opportunities
InterpersonalBonding
SocialCompetence
Interactions w/Social Instit’s
Others’Beh & Atts
Motivationto Comply
Skills:Social+General
Sense ofSelf/Control
SelfDetermination
1 2 3
7 8 9 10 11 12
13 14 15 16 17 18
l
4 5 6
19 20 21
22
23
DistalInfluences
ProximalPredictors
Levels ofCausation
UltimateCauses
Social/Personal Nexus
Expectancies & Evaluations
Affect andCognitions
Decisions
Experiences
a
b c d e
f
g h i
jk m n
o
p q r
s
t u v w
x
Related BehaviorsJ
K
CF
IB E HA D G
CULTURALENVIRONMENT
Discussion
Why do you think Carpenter found perceived susceptibility to have almost no relationship to health behavior?
Why do you think time between measures worked as a moderator for susceptibility, severity, and benefits?
Why was time between measurements not a moderator for barriers?
References Christopher J. Carpenter (2010): A Meta-Analysis of the
Effectiveness of Health Belief Model Variables in Predicting Behavior, Health Communication, 25:8, 661-669.
DiClemente, R.J., Salazar, L.F., & Crosby, R.A. (2013). Health Behavior Theory for Public Health: Principles, Foundations and Applications. Jones and Bartlett, Boston, MA.
TTI slides provided to H 571 class at Oregon State University.