1 modeling change in health status: patterns over time susan j. henly, phd, rn methods director...
TRANSCRIPT
![Page 1: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/1.jpg)
1
Modeling Change in Health Status: Patterns over Time
Susan J. Henly, PhD, RNMethods DirectorMinnesota Center for Health Trajectory Research
Seminar: September 24, 2008
![Page 2: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/2.jpg)
2
Post-Op Day
876543210
Pa
in:
Se
lf-R
ep
ort
12
10
8
6
4
2
0
-2
Pain at bedtime over the 1st post-op week
Busch, S.E. (2002). Sleep patterns following an out-patient surgical procedure. Unpublished MS thesis. Busch, S.E. (2002). Sleep patterns following an out-patient surgical procedure. Unpublished MS thesis. University of Minnesota, Minneapolis. University of Minnesota, Minneapolis.
![Page 3: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/3.jpg)
Why study change in health status?
Within persons, health status varies over time
Accurate description of health status over time is essential to understanding health behaviors and illness responses
Intervention assumes that health status is malleable-- intra-individual change can be predicted and “controlled” (influenced by nursing actions)
Inter-individual differences in intra-individual change can be explained
![Page 4: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/4.jpg)
Some ideas about change
To be or cause to be different
To alter the course of
Naturalistic change
Experimentally induced change
![Page 5: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/5.jpg)
Operationalizing change
Increment: difference on 2 occasions
Rate: speed, velocity, pace
Pattern: form, shape, model
![Page 6: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/6.jpg)
Changing ideas about studying change
![Page 7: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/7.jpg)
Health as a function of time
![Page 8: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/8.jpg)
Purpose
Describe mathematical functions that can be used to model change in health status
Characterize intra-individual change using personalized functions
Recognize that variation in parameters of personalized functions represents inter-individual differences in change
Comment on formulation of hypotheses to explain inter-individual differences in change using parameters of personalized functions
![Page 9: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/9.jpg)
About functions
A function is a rule that maps every point in a defined domain t with one and only one value in its range H
Function rules are defined by their parameters
Functions can be described using equations
Functions can be displayed in tables
Functions can be depicted by their graphs
![Page 10: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/10.jpg)
The general function
Time ► Function ► Health
Hi = fi (t)
For each person, at each point in time, for any given indicator of health status,there is one and only one value for health status.
![Page 11: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/11.jpg)
Time is the primary “predictor” variable
Health status is “outcome”
Health as a function of time shows patterns of change
Each person follows their own pattern: everyone has their own set of parameters
Hi (t): key features
![Page 12: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/12.jpg)
Functions describing change of many kinds
Function Rule Parameters
Constant H (t) = κ κ
Linear H (t) = π0 + π1t π0 , π1
Quadratic H (t) = π0 + π1t + π2t2 π0 , π1 , π2
Polynomial H (t) = πntn + πn-1tn-1+ … + π1t + π0 π0 to πn
Exponential H (t) = α + (ξ – α) exp (ρt) α, ξ, ρ
Sine H (t) = α sin (ωt + θ) + δ α, ω , θ, δ
Piece-wise H (t) = H1 (t), t < tt,
H (t) = H2 (t), t ≥ tt,
Parameters of
H1 and H2
![Page 13: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/13.jpg)
13
Change functions
-2
-1
0
1
2
3
4
5
6
7
8
9
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
Time
Hea
lth
Constant
Linear
Quadratic
Polynomial
Exponential
Sine
Piece-wise
![Page 14: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/14.jpg)
Constant functions: Hi (t) = κi
i κi t Hi (t)
1 -.5 -3 -.5
0 -.5
4 -.5
2 5 -2 5
0 5
6 5
3 8 -4 8
-1 8
0 8
For person i, κi gives the function value at every time t
![Page 15: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/15.jpg)
15
Constant functions Hi (t) = κi
-2
-1
0
1
2
3
4
5
6
7
8
9
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
Time
He
alth
![Page 16: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/16.jpg)
16
Linear functions: Hi (t) = π0i + π1i t
i π0i π1i t Hi (t)
1 1.21 .18 -5 0.36
0 1.21
8 2.58
2 1.48 .45 0 1.48
1 1.93
8 5.13
3 4.01 .27 -2 3.48
1 4.28
2 4.55
For person i, π0i gives the function value at t0 (intercept) and π1i gives the rate of change over time (slope). Note that selection of t0 is critical to scientific interpretation of the parameters.
![Page 17: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/17.jpg)
17
Linear functionsHi (t) = π0i + π1it
-2
-1
0
1
2
3
4
5
6
7
8
9
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
Time
He
alth
![Page 18: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/18.jpg)
Quadratic and higher order polynomial functions
General polynomial form is:
H (t) = πntn + πn-1tn-1+ … + π1t + π0
Quadratic:
H (t) = π2t2 + π1t + π0
Cubic:
H (t) = π3t3 + π2t2+ π1t + π0
And so on with higher order functions of time
Polynomial Equation Grapherhttp://www.math.umn.edu/~garrett/qy/Quintic.html
![Page 19: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/19.jpg)
Exponential functions
![Page 20: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/20.jpg)
Exploring sine functions for periodic change
Variations on the Sine Function
The website is:
http://www.analyzemath.com/trigonometry/sine.htm
![Page 21: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/21.jpg)
21
For person i, κi gives the baseline value, π0i gives the function value at the transition point, which is also the intercept in the example and π1i gives the rate of change over time (slope) after the transition. In this example, the time of transition is known. Sometimes, the transition point is itself a parameter to be estimated.
Piece-wise functions (ex)H1i (t) = κi, t < 0H2i (t) = π0i + π1it, t ≥ 0
i κi π0i π1i t Hi (t)
1 3.91 3.91 .30 -1 3.91
2 4.52
4 5.14
2 5.02 5.02 .37 -2 5.02
0 5.02
5 6.88
3 3.54 3.54 .31 0 3.54
3 4.47
7 5.70
![Page 22: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/22.jpg)
22
Piece-wise functions (ex)H1i (t) = κi, t < 0H2i (t) = π0i + π1it, t ≥ 0
-2
-1
0
1
2
3
4
5
6
7
8
9
10
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
Time
Hea
lth
![Page 23: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/23.jpg)
Statistical models for individual change
Longitudinal data on 3 or more occasions
Sensible metric for time
Theory about change
Graphs of individual cases to identify form of change
Personal parameters estimated to produce smoothed curves for each persons change pattern
Random coefficients in a mixed effects model
![Page 24: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/24.jpg)
24
Linear change: variation around the least squares fit line for 3 example persons
-2
-1
0
1
2
3
4
5
6
7
8
9
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
Time
Hea
lth
![Page 25: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/25.jpg)
25
Piece-wise change: variation around the least squares fit line for 3 example persons
-2
-1
0
1
2
3
4
5
6
7
8
9
10
-6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
Time
Hea
lth
![Page 26: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/26.jpg)
Theory about change
Longitudinal ( ≥ 3 occasions of observation)
Measurement sensitive to individual change
Statistical models linking intra- and inter-individual change (mixed effects models)
Describing and explaining patterns of change
![Page 27: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/27.jpg)
27
Heart soft-touch project
![Page 28: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/28.jpg)
Heart soft-touch outcomes: pain/tension mean comparisons
POD SC AIT t p
1 Mean 3.5 2.4 -2.52 .01
SD 2.6 1.9
2 Mean 2.1 1.3 -2.10 .04
SD 2.0 1.3
![Page 29: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/29.jpg)
29
Heart soft-touch outcomes: ITV vs SC
Measurement Time
4.03.53.02.52.01.51.0.50.0-.5-1.0
Pa
in/T
en
sio
n (
Me
an
)
11
10
9
8
7
6
5
4
3
2
1
0
-1
Condition
SC
ITP
![Page 30: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/30.jpg)
30
Heart soft-touch outcomes
SC vs AIT Standard Care Integrative Therapies
Measurement Time
4.03.53.02.52.01.51.0.50.0-.5-1.0
Pa
in/T
en
sio
n (
Me
an
)
11
10
9
8
7
6
5
4
3
2
1
0
-1
Condition
SC
ITP
Time of Observation
4.03.53.02.52.01.51.0.50.0-.5-1.0
Pai
n/Te
nsio
n
11
10
9
8
7
6
5
4
3
2
1
0
-1
Time of Observation
4.03.53.02.52.01.51.0.50.0-.5-1.0
Pa
in/T
en
sio
n
11
10
9
8
7
6
5
4
3
2
1
0
-1
![Page 31: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/31.jpg)
31
Heart soft-touch outcomes
ITP vs SC SC
Measurement Time
4.03.53.02.52.01.51.0.50.0-.5-1.0
Pa
in/T
en
sio
n (
Me
an
)
11
10
9
8
7
6
5
4
3
2
1
0
-1
Condition
SC
ITP
Time of Observation
4.03.53.02.52.01.51.0.50.0-.5-1.0
Pai
n/Te
nsio
n
11
10
9
8
7
6
5
4
3
2
1
0
-1
Time of Observation
4.03.53.02.52.01.51.0.50.0-.5-1.0
Pa
in/T
en
sio
n
11
10
9
8
7
6
5
4
3
2
1
0
-1
ITP
![Page 32: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/32.jpg)
Nursing practice: people and change
Baby is off to a healthy start.
Patient is going downhill fast.
She recovered quickly after the nurse lifted her spirits.
He had a rocky post-op course.
When he exercised regularly, his glucose levels decreased and stabilized.
She reacted to her husband’s death with an intense sense of depression, but soon returned to her usual sunny self.
![Page 33: 1 Modeling Change in Health Status: Patterns over Time Susan J. Henly, PhD, RN Methods Director Minnesota Center for Health Trajectory Research Seminar:](https://reader035.vdocuments.site/reader035/viewer/2022062719/56649ee45503460f94bf3c0e/html5/thumbnails/33.jpg)
33
Person
Environment
NursingHealth
TIME
Time for change in the nursing metaparadigm