## Loading required package: MASS
We (HANDLS) don't know anything about circadian rhythm measures. Let's start by examining descriptive statistics and interrelationships among the measures and with age.
zVsel(w03Circadian, Age0, Sex, Race, PovStat)
4 Variables 80 Observations
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Age0 : Initial age
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
80 0 30 46.05 33.00 35.00 39.00 46.00 52.00 59.10 62.05
lowest : 32 33 34 35 36, highest: 59 60 61 62 63
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Sex
n missing unique
80 0 2
Women (49, 61%), Men (31, 39%)
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Race
n missing unique
80 0 2
White (31, 39%), AfrAm (49, 61%)
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PovStat : Poverty status
n missing unique
80 0 2
Above (41, 51%), Below (39, 49%)
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N Mean SD Min Max
CRmeanNonzeroCS 80 0.18 0.07 0.05 0.35 Mean illuminance exposure (circadian system activation)
CRmeanLogLux 80 10.33 9.12 0.37 62.89 Mean log illuminance exposure (circadian system activation)
CSphasorMag 80 0.29 0.10 0.03 0.51 Phasor magnitude (circadian entrainment)
CSphasorAngleHrs 80 1.72 1.50 -2.11 5.40 Phasor angle (night-owl: positive; lark: negative)
CSinterdayStab 80 0.58 0.15 0.11 0.88 Interday stability (day-by-day regularity of the activity-rest pattern)
CSintradayVar 80 0.55 0.16 0.26 1.29 Intradaily variability (fragmentation of rhythm frequency)
CRmeanNonzeroCS CRmeanLogLux CSphasorMag CSphasorAngleHrs CSinterdayStab CSintradayVar Age0
CRmeanNonzeroCS 1.00 0.41*** 0.49*** -0.11 0.14 -0.20 -0.16
CRmeanLogLux 0.41*** 1.00 0.34** -0.07 0.16 -0.21 -0.13
CSphasorMag 0.49*** 0.34** 1.00 -0.05 0.76*** -0.62*** 0.01
CSphasorAngleHrs -0.11 -0.07 -0.05 1.00 -0.03 0.19 -0.18
CSinterdayStab 0.14 0.16 0.76*** -0.03 1.00 -0.51*** 0.15
CSintradayVar -0.20 -0.21 -0.62*** 0.19 -0.51*** 1.00 0.10
Age0 -0.16 -0.13 0.01 -0.18 0.15 0.10 1.00
n = 80
The circadian rhythm measures are moderately intercorrelated, most notably phasor magnitude is correlated with interday stability (r = 0.76) and intradaily variability (r = -0.62).
Relationships assessed by regression. Rsq (R2) represents proportion of variance in outcome (circadian measures) by covariates (sex, race, etc). Other table entries are regression coefficients interpreted as amount of outcome associated with one unit change in the covariate (e.g., difference in CRmeanNonzeroCS associated with sex). Covariate label indicates direction of comparison (e.g., SexMen for the differences in outcome, men – women).
CRmeanNonzeroCS CRmeanLogLux CSphasorMag CSphasorAngleHrs CSinterdayStab CSintradayVar
Rsq 0.014 0.000 0.087 ** 0.015 0.144 *** 0.039
SexMen 0.016 0.360 -0.058 ** 0.378 -0.115 *** 0.066
CRmeanNonzeroCS CRmeanLogLux CSphasorMag CSphasorAngleHrs CSinterdayStab CSintradayVar
Rsq 0.023 0.003 0.057 * 0.015 0.067 * 0.023
RaceAfrAm -0.021 0.956 -0.047 * 0.377 -0.079 * 0.050
CRmeanNonzeroCS CRmeanLogLux CSphasorMag CSphasorAngleHrs CSinterdayStab CSintradayVar
Rsq 0.045 0.020 0.000 0.064 * 0.000 0.001
PovStatBelow -0.028 -2.532 0.000 0.754 * 0.002 -0.011
CRmeanNonzeroCS CRmeanLogLux CSphasorMag CSphasorAngleHrs CSinterdayStab CSintradayVar
Rsq 0.010 0.016 0.002 0.032 0.002 0.017
Age0medAbove -0.014 -2.334 -0.009 -0.544 0.013 0.043
There are sex differences on only CSphasorMag. We can leave it aside for now. Age is not correlated significantly with any of the circadian rhythm measures. Nor are there differences in any circadian rhythm measures by median age.
Are the circadian rhythm measures associated with race, poverty status, and their interaction?
CRmeanNonzeroCS CRmeanLogLux CSphasorMag CSphasorAngleHrs CSinterdayStab CSintradayVar
Rsq 0.114 * 0.038 0.115 * 0.083 0.095 0.025
RaceAfrAm 0.006 3.199 -0.000 0.322 -0.029 0.038
PovStatBelow 0.005 0.404 0.056 0.661 0.061 -0.024
RaceAfrAm:PovStatBelow -0.056 -4.738 -0.095 * 0.182 -0.101 0.024
There are no significant main effects for race or poverty status, but there is a significant race × poverty status interaction on CSphasorMag.
Call:
lm(formula = CSphasorMag ~ (Sex + Race + PovStat)^3, data = w03Circadian)
Residuals:
Phasor magnitude (circadian entrainment)
Min 1Q Median 3Q Max
-0.2015 -0.0620 0.0054 0.0607 0.1669
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 0.286333 0.029608 9.67 1.2e-14
SexMen 0.000167 0.046814 0.00 0.9972
RaceAfrAm 0.034792 0.037010 0.94 0.3503
PovStatBelow 0.083667 0.040812 2.05 0.0440
SexMen:RaceAfrAm -0.090792 0.058938 -1.54 0.1278
SexMen:PovStatBelow -0.073333 0.065540 -1.12 0.2669
RaceAfrAm:PovStatBelow -0.138720 0.052175 -2.66 0.0097
SexMen:RaceAfrAm:PovStatBelow 0.117331 0.083772 1.40 0.1656
Residual standard error: 0.0888 on 72 degrees of freedom
Multiple R-squared: 0.227, Adjusted R-squared: 0.152
F-statistic: 3.03 on 7 and 72 DF, p-value: 0.00758
Step 1:
Call:
lm(formula = CSphasorMag ~ (Sex + Race + PovStat)^2, data = w03Circadian)
Residuals:
Phasor magnitude (circadian entrainment)
Min 1Q Median 3Q Max
-0.2147 -0.0594 0.0118 0.0610 0.1751
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 0.30099 0.02788 10.80 <2e-16
SexMen -0.03647 0.03908 -0.93 0.354
RaceAfrAm 0.01189 0.03342 0.36 0.723
PovStatBelow 0.05582 0.03588 1.56 0.124
SexMen:RaceAfrAm -0.03271 0.04216 -0.78 0.440
SexMen:PovStatBelow -0.00152 0.04109 -0.04 0.971
RaceAfrAm:PovStatBelow -0.09321 0.04109 -2.27 0.026
Residual standard error: 0.0894 on 73 degrees of freedom
Multiple R-squared: 0.206, Adjusted R-squared: 0.141
F-statistic: 3.16 on 6 and 73 DF, p-value: 0.00817
Step 2:
Call:
lm(formula = CSphasorMag ~ Sex + Race * PovStat, data = w03Circadian)
Residuals:
Phasor magnitude (circadian entrainment)
Min 1Q Median 3Q Max
-0.2220 -0.0598 0.0084 0.0564 0.1797
Coefficients:
Estimate Std. Error t value Pr(>|t|)
(Intercept) 0.30930 0.02427 12.74 <2e-16
SexMen -0.05726 0.02033 -2.82 0.0062
RaceAfrAm -0.00101 0.02872 -0.04 0.9720
PovStatBelow 0.05473 0.03184 1.72 0.0897
RaceAfrAm:PovStatBelow -0.09279 0.04070 -2.28 0.0255
Residual standard error: 0.0886 on 75 degrees of freedom
Multiple R-squared: 0.2, Adjusted R-squared: 0.157
F-statistic: 4.68 on 4 and 75 DF, p-value: 0.00199
Is this sex difference meaningful?
Sex CSphasorMag.n CSphasorMag.mean CSphasorMag.sd CSphasorMag.min CSphasorMag.max
1 Women 49 0.309 0.08361 0.173 0.508
2 Men 31 0.251 0.10580 0.029 0.420
Graphically, the race × poverty status difference is apparent in only women, though for men there's an apparent main effect for race. We should probably take care in over-interpreting these differences because the sample sizes are rather small in each demographic group.
Sex Race PovStat CSphasorMag.n CSphasorMag.mean CSphasorMag.sd CSphasorMag.min CSphasorMag.max
1 Women White Above 9 0.2863 0.07494 0.173 0.373
2 Women White Below 10 0.3700 0.08572 0.206 0.508
3 Women AfrAm Above 16 0.3211 0.08687 0.194 0.488
4 Women AfrAm Below 14 0.2661 0.05639 0.191 0.366
5 Men White Above 6 0.2865 0.07717 0.204 0.385
6 Men White Below 6 0.2968 0.11270 0.127 0.420
7 Men AfrAm Above 10 0.2305 0.13884 0.029 0.374
8 Men AfrAm Below 9 0.2194 0.06679 0.098 0.330
Here are associations of circadian rhythm measures with select health measures adjusted for age, sex, race, & poverty status.
N Mean SD Min Max
PhysBMI 77 31.93 7.66 15.4 51.0 PhysExam-BodyComp: BMI
PhysBPdiaSit 72 70.69 10.94 50.0 100.0 PhysExam BP diastolic (seated)
PhysBPsysSit 72 119.88 16.23 90.0 162.0 PhysExam BP systolic (seated)
Chol 74 188.58 40.85 82.0 301.0 Total cholesterol
LDLcalc 73 112.70 36.27 30.0 196.0 LDL cholesterol
HDL 74 51.73 15.20 26.0 99.0 HDL cholesterol
Glucose 74 105.24 33.58 75.0 281.0 Fasting glucose
CRPcard 54 0.54 0.61 0.1 3.1 C-reaactive protein (low-sensitivity assay)
CRmeanNonzeroCS -- Mean illuminance exposure (circadian system activation)
PhysBMI PhysBPdiaSit PhysBPsysSit Chol LDLcalc HDL Glucose CRPcard
Rsq 0.131 0.267 * 0.229 * 0.069 0.072 0.298 ** 0.276 ** 0.407 **
CRmeanNonzeroCS -20.741 -27.916 10.891 725.652 504.520 351.814 * -197.516 -6.689
Age0 -0.034 -0.276 0.417 2.284 1.457 1.020 -0.657 -0.018
SexMen -1.838 -7.796 -20.634 16.900 21.959 3.665 -25.231 -0.358
RaceAfrAm -7.098 14.829 13.095 22.136 0.772 20.435 -32.895 0.604
PovStatBelow 8.054 18.460 * 27.239 * -22.292 -32.774 1.833 32.121 -0.184
CRmeanNonzeroCS:Age0 1.005 1.485 0.527 -12.803 -9.952 -6.430 5.286 0.188
CRmeanNonzeroCS:SexMen -4.110 51.653 101.461 -141.904 -126.558 -70.193 182.099 1.201
CRmeanNonzeroCS:RaceAfrAm 37.237 -42.143 -40.547 -129.458 -53.648 -58.195 220.727 -2.992
CRmeanNonzeroCS:PovStatBelow -51.687 -83.029 * -140.314 * 71.738 126.737 -4.864 -203.870 3.364
CRmeanLogLux -- Mean log illuminance exposure (circadian system activation)
PhysBMI PhysBPdiaSit PhysBPsysSit Chol LDLcalc HDL Glucose CRPcard
Rsq 0.181 0.195 0.138 0.068 0.101 0.292 ** 0.134 0.271
CRmeanLogLux 2.254 * 0.390 1.000 4.691 5.146 0.653 4.290 -0.083
Age0 0.376 -0.077 0.478 0.614 0.518 0.107 0.211 -0.001
SexMen -4.064 1.589 -3.180 -7.528 4.779 -13.379 * 13.801 -0.256
RaceAfrAm 2.830 12.088 * 15.653 21.805 6.267 14.980 * 15.023 0.120
PovStatBelow 2.951 6.219 6.134 -16.401 -28.616 -0.651 -4.516 -0.079
CRmeanLogLux:Age0 -0.037 0.004 -0.002 -0.068 -0.088 -0.019 -0.056 0.002
CRmeanLogLux:SexMen 0.174 0.130 0.285 -0.255 -0.731 0.343 -0.042 0.022
CRmeanLogLux:RaceAfrAm -0.493 -0.484 -0.946 -2.392 -1.596 -0.367 -1.313 -0.014
CRmeanLogLux:PovStatBelow -0.547 * -0.269 -0.498 0.639 1.940 0.204 -0.946 0.054
CSphasorMag -- Phasor magnitude (circadian entrainment)
PhysBMI PhysBPdiaSit PhysBPsysSit Chol LDLcalc HDL Glucose CRPcard
Rsq 0.099 0.248 * 0.211 0.088 0.101 0.309 ** 0.208 0.287
CSphasorMag -29.105 -16.674 56.515 559.009 573.533 * 211.093 * 200.717 -9.319
Age0 -0.080 -0.139 0.766 3.125 2.927 1.004 0.322 -0.028
SexMen 4.946 -15.361 -27.293 * 9.469 10.532 -14.174 13.773 -0.507
RaceAfrAm -10.480 15.830 20.807 13.863 1.700 28.172 * 1.172 -0.170
PovStatBelow -7.540 17.844 30.847 * -7.400 -17.039 18.166 1.639 -0.395
CSphasorMag:Age0 0.436 0.447 -0.938 -11.017 -11.455 * -3.727 -2.049 0.167
CSphasorMag:SexMen -19.167 60.859 * 86.199 * -79.099 -49.896 7.180 23.859 2.133
CSphasorMag:RaceAfrAm 37.611 -31.871 -56.533 -52.073 -30.692 -63.251 24.227 0.868
CSphasorMag:PovStatBelow 20.549 -50.901 -104.681 * -6.245 25.322 -59.415 -54.032 2.937
CSphasorAngleHrs -- Phasor angle (night-owl: positive; lark: negative)
PhysBMI PhysBPdiaSit PhysBPsysSit Chol LDLcalc HDL Glucose CRPcard
Rsq 0.077 0.308 ** 0.189 0.078 0.073 0.304 ** 0.243 * 0.335 *
CSphasorAngleHrs 0.509 -13.729 * -17.629 -2.565 2.583 -3.193 -9.157 -0.203
Age0 0.050 -0.388 0.021 0.142 -0.077 -0.081 -0.424 0.005
SexMen -0.727 0.034 -4.603 -30.066 -17.515 -11.534 * -9.792 -0.181
RaceAfrAm 0.190 -1.980 -3.209 8.292 3.002 9.434 -2.197 -0.207
PovStatBelow -2.803 2.395 3.888 -11.238 -8.813 -6.429 -6.280 0.938 ***
CSphasorAngleHrs:Age0 0.022 0.211 0.292 -0.069 -0.119 -0.015 0.165 0.004
CSphasorAngleHrs:SexMen -0.849 1.807 2.991 12.461 9.232 1.002 13.352 * 0.038
CSphasorAngleHrs:RaceAfrAm -0.485 6.079 ** 6.738 * -4.941 -6.921 1.424 4.305 0.072
CSphasorAngleHrs:PovStatBelow -0.095 -0.232 -2.554 2.241 0.430 5.307 * -6.602 -0.301 **
CSinterdayStab -- Interday stability (day-by-day regularity of the activity-rest pattern)
PhysBMI PhysBPdiaSit PhysBPsysSit Chol LDLcalc HDL Glucose CRPcard
Rsq 0.112 0.247 * 0.133 0.060 0.101 0.249 * 0.170 0.214
CSinterdayStab 16.586 -41.702 -74.722 236.750 326.477 -9.795 64.683 -2.118
Age0 0.208 -0.126 0.040 2.816 3.107 0.114 0.046 0.000
SexMen 10.499 -23.202 -19.655 13.185 18.310 -19.207 27.339 -0.862
RaceAfrAm -11.697 3.334 -0.003 6.202 12.887 12.736 -24.526 -0.177
PovStatBelow -10.300 11.594 5.094 -4.851 25.837 6.784 -28.121 -0.308
CSinterdayStab:Age0 -0.353 0.228 0.866 -4.680 -5.758 -0.139 -0.875 0.027
CSinterdayStab:SexMen -18.392 43.687 * 32.226 -46.188 -47.024 13.048 -6.081 1.505
CSinterdayStab:RaceAfrAm 20.434 7.275 11.530 -14.720 -43.281 -3.602 58.385 0.313
CSinterdayStab:PovStatBelow 14.083 -11.879 -4.435 -7.662 -64.295 -7.603 25.719 1.269
CSintradayVar -- Intradaily variability (fragmentation of rhythm frequency)
PhysBMI PhysBPdiaSit PhysBPsysSit Chol LDLcalc HDL Glucose CRPcard
Rsq 0.067 0.229 * 0.184 0.125 0.136 0.262 * 0.157 0.249
CSintradayVar 23.931 13.850 -26.343 -318.798 -391.233 * -58.672 54.616 2.997
Age0 0.239 0.189 0.616 -2.672 -3.851 -0.501 1.550 0.050
SexMen -4.813 6.398 -14.400 -38.328 -18.103 -18.855 -9.269 0.270
RaceAfrAm 3.412 -6.612 -12.796 -29.731 -41.361 11.564 9.564 0.023
PovStatBelow 0.038 -10.367 -28.033 -87.879 * -63.136 -12.083 -55.860 1.341 *
CSintradayVar:Age0 -0.343 -0.520 -0.416 4.555 6.245 0.800 -3.137 -0.056
CSintradayVar:SexMen 5.243 -6.225 27.080 50.926 27.413 17.197 50.189 -0.564
CSintradayVar:RaceAfrAm -7.377 25.548 35.379 49.073 58.142 -0.788 -6.568 -0.099
CSintradayVar:PovStatBelow -4.043 24.836 53.793 144.530 * 95.050 25.955 78.979 -1.645
We also collected data on the sleep with the Ludwig Sleep Questionnaire.
Here are descriptive statistics.
zVsel(w03Circadian, LMworkRegSch:LMfreeDaylight)
17 Variables 80 Observations
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LMworkRegSch : Regular work schedule
n missing unique
80 0 2
No (43, 54%), Yes (37, 46%)
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LMworkDays : # days/week worked
n missing unique Mean
37 43 5 4.676
3 4 5 6 7
Frequency 7 5 19 5 1
% 19 14 51 14 3
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LMworkBed : Work day: bed time
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
80 0 80 45.12 6.95 10.90 22.75 44.50 67.25 80.10 84.05
lowest : 3 4 5 6 7, highest: 84 85 86 87 88
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LMworkReady : Work day: time ready to sleep
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
80 0 80 45.12 6.95 10.90 22.75 44.50 67.25 80.10 84.05
lowest : 3 4 5 6 7, highest: 84 85 86 87 88
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LMworkAsleep : Work day: minutes to sleep
n missing unique Mean
40 40 8 24.75
0 5 10 15 20 30 45 60
Frequency 2 2 7 7 5 10 1 6
% 5 5 18 18 12 25 2 15
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LMworkAwake : Work day: awake time
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
80 0 80 45.12 6.95 10.90 22.75 44.50 67.25 80.10 84.05
lowest : 3 4 5 6 7, highest: 84 85 86 87 88
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LMworkAlarm : Work day: use alarm clock
n missing unique
38 42 2
No (14, 37%), Yes (24, 63%)
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LMworkGetup : Work day: minutes until get up
n missing unique Mean
35 45 8 12.91
0 2 3 5 10 15 20 30
Frequency 3 2 1 7 6 6 4 6
% 9 6 3 20 17 17 11 17
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LMfreeBed : Free day: bed time
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
80 0 80 45.12 6.95 10.90 22.75 44.50 67.25 80.10 84.05
lowest : 3 4 5 6 7, highest: 84 85 86 87 88
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LMfreeReady : Free day: time ready to sleep
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
80 0 80 45.12 6.95 10.90 22.75 44.50 67.25 80.10 84.05
lowest : 3 4 5 6 7, highest: 84 85 86 87 88
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LMfreeAsleep : Free day: minutes to sleep
n missing unique Mean
78 2 9 27.03
3 5 10 15 20 30 45 60 90
Frequency 1 10 11 14 5 21 1 13 2
% 1 13 14 18 6 27 1 17 3
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LMfreeAwake : Free day: awake time
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
80 0 80 45.12 6.95 10.90 22.75 44.50 67.25 80.10 84.05
lowest : 3 4 5 6 7, highest: 84 85 86 87 88
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LMfreeAlarm : Free day: use alarm clock
n missing unique
80 0 2
No (66, 82%), Yes (14, 18%)
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LMfreeGetup : Free day: minutes until get up
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
75 5 12 23.08 4.4 5.0 5.0 10.0 30.0 60.0 90.0
2 3 5 6 10 15 20 25 30 60 90 99
Frequency 1 3 23 1 13 5 2 1 13 8 4 1
% 1 4 31 1 17 7 3 1 17 11 5 1
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LMcomment
n missing unique
29 51 24
lowest : currently unemployed No currently working. Not currently at a full time job. not currently working
highest: Pt says she wakes up at 7.00am on off days because of her children. Does not work. During school days wake up to help children get ready for school then go back to sleep to wake up later at 10:00am. On none school day wake up around 10:00am Pt wakes up to get his children ready for school, then comes home and goes back to bed. Pt works evening shift from 12 noon to 12 am.
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LMworkDaylight : Work day: minutes spent outdoors in daylight
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
36 44 14 226.9 30.0 60.0 82.5 180.0 315.0 480.0 630.0
10 30 60 90 120 180 240 300 360 420 540 600 720 780
Frequency 1 2 6 2 6 3 5 2 4 1 1 1 1 1
% 3 6 17 6 17 8 14 6 11 3 3 3 3 3
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LMfreeDaylight : Free day: minutes spent outdoors in daylight
n missing unique Mean .05 .10 .25 .50 .75 .90 .95
74 6 16 229.8 54.75 78.00 120.00 240.00 300.00 360.00 421.50
10 30 45 60 120 150 180 210 240 300 330 360 390 480 540 600
Frequency 1 2 1 4 14 1 11 2 12 8 1 12 1 2 1 1
% 1 3 1 5 19 1 15 3 16 11 1 16 1 3 1 1
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