Relationships among circadian rhythm measures

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
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Age0 
      n missing  unique    Info    Mean     .05     .10     .25     .50     .75     .90     .95 
     80       0      30       1   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 
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Sex 
      n missing  unique 
     80       0       2 

Women (49, 61%), Men (31, 39%) 
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Race 
      n missing  unique 
     80       0       2 

White (31, 39%), AfrAm (49, 61%) 
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
PovStat : Poverty status 
      n missing  unique 
     80       0       2 

Above (41, 51%), Below (39, 49%) 
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                  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 of demographic indicators and circadian rhythm measures

Separately by sex, race, poverty status, & age

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?

Complete model

                       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.

Phasor magnitude (circadian entrainment) by sex, race, & poverty status

Complete model


Call:
lm(formula = CSphasorMag ~ (Sex + Race + PovStat)^3, data = w03Circadian)

Residuals:
Phasor magnitude (circadian entrainment) 
         Min           1Q       Median           3Q          Max 
-0.201500000 -0.062017857  0.005401786  0.060750000  0.166875000 

Coefficients:
                                   Estimate    Std. Error  t value   Pr(>|t|)
(Intercept)                    0.2863333333  0.0296079249  9.67083 1.1918e-14
SexMen                         0.0001666667  0.0468142398  0.00356  0.9971692
RaceAfrAm                      0.0347916667  0.0370099062  0.94006  0.3503281
PovStatBelow                   0.0836666667  0.0408117081  2.05007  0.0440004
SexMen:RaceAfrAm              -0.0907916667  0.0589376220 -1.54047  0.1278295
SexMen:PovStatBelow           -0.0733333333  0.0655399357 -1.11891  0.2668974
RaceAfrAm:PovStatBelow        -0.1387202381  0.0521751551 -2.65874  0.0096588
SexMen:RaceAfrAm:PovStatBelow  0.1173313492  0.0837718926  1.40061  0.1656272

Residual standard error: 0.08882377 on 72 degrees of freedom
Multiple R-squared:  0.227421,  Adjusted R-squared:  0.1523091 
F-statistic: 3.027764 on 7 and 72 DF,  p-value: 0.007576951

After backward elimination of nonsignificant interactions (2 steps)

Step 1:


Call:
lm(formula = CSphasorMag ~ (Sex + Race + PovStat)^2, data = w03Circadian)

Residuals:
Phasor magnitude (circadian entrainment) 
        Min          1Q      Median          3Q         Max 
-0.21469094 -0.05937123  0.01184871  0.06102953  0.17511934 

Coefficients:
                           Estimate   Std. Error  t value Pr(>|t|)
(Intercept)             0.300989937  0.027878843 10.79636  < 2e-16
SexMen                 -0.036474843  0.039077104 -0.93341 0.353687
RaceAfrAm               0.011890723  0.033420187  0.35579 0.723020
PovStatBelow            0.055819119  0.035875003  1.55593 0.124049
SexMen:RaceAfrAm       -0.032714873  0.042158820 -0.77599 0.440261
SexMen:PovStatBelow    -0.001515974  0.041087851 -0.03690 0.970669
RaceAfrAm:PovStatBelow -0.093206248  0.041087851 -2.26846 0.026259

Residual standard error: 0.08940694 on 73 degrees of freedom
Multiple R-squared:  0.2063715, Adjusted R-squared:  0.1411417 
F-statistic: 3.163763 on 6 and 73 DF,  p-value: 0.008168384

Step 2:


Call:
lm(formula = CSphasorMag ~ Sex + Race * PovStat, data = w03Circadian)

Residuals:
Phasor magnitude (circadian entrainment) 
        Min          1Q      Median          3Q         Max 
-0.22203274 -0.05978743  0.00839775  0.05640094  0.17970796 

Coefficients:
                           Estimate   Std. Error  t value   Pr(>|t|)
(Intercept)             0.309303719  0.024271323 12.74359 < 2.22e-16
SexMen                 -0.057259296  0.020328897 -2.81665  0.0061986
RaceAfrAm              -0.001011681  0.028719139 -0.03523  0.9719925
PovStatBelow            0.054731018  0.031835861  1.71916  0.0897098
RaceAfrAm:PovStatBelow -0.092791156  0.040699700 -2.27990  0.0254571

Residual standard error: 0.08856988 on 75 degrees of freedom
Multiple R-squared:  0.1998244, Adjusted R-squared:  0.1571484 
F-statistic: 4.682357 on 4 and 75 DF,  p-value: 0.001988525

Is this sex difference meaningful?

    Sex CSphasorMag.n CSphasorMag.mean CSphasorMag.sd CSphasorMag.min CSphasorMag.max
1 Women            49     0.3089795918  0.08361381709           0.173           0.508
2   Men            31     0.2509677419  0.10579712783           0.029           0.420

plot of chunk CSphasorMag.SexDiff

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     0.2863333333  0.07494331191           0.173           0.373
2 Women White   Below            10     0.3700000000  0.08571529100           0.206           0.508
3 Women AfrAm   Above            16     0.3211250000  0.08687145676           0.194           0.488
4 Women AfrAm   Below            14     0.2660714286  0.05639075795           0.191           0.366
5   Men White   Above             6     0.2865000000  0.07717188607           0.204           0.385
6   Men White   Below             6     0.2968333333  0.11270388931           0.127           0.420
7   Men AfrAm   Above            10     0.2305000000  0.13884063606           0.029           0.374
8   Men AfrAm   Below             9     0.2194444444  0.06678531109           0.098           0.330

plot of chunk CSphasorMag.demogDiff

Associations of circadian rhythm measures with health-risk factors

Here are associations of circadian rhythm measures with select health measures adjusted for age, sex, race, & poverty status.

           N   Mean    SD   Min   Max                                            
BMI       77  31.93  7.66 15.40  51.0                                            
BPsitRdia 76  70.24 10.80 50.00  96.0                                            
BPsitRsys 76 121.41 16.24 90.00 164.0                                            
Chol      74 188.58 40.85 82.00 301.0 Total cholesterol                          
LDLcalc   73 112.70 36.27 30.00 196.0 LDL cholesterol                            
HDL       74  51.73 15.20 26.00  99.0 HDL cholesterol                            
Glucose   74 105.24 33.58 75.00 281.0 Fasting glucose                            
CRPLS     74   0.42  0.56  0.09   3.1 C-reaactive protein (low-sensitivity assay)


CRmeanNonzeroCS -- Mean illuminance exposure (circadian system activation)

                                 BMI     BPsitRdia     BPsitRsys         Chol      LDLcalc         HDL      Glucose      CRPLS    
Rsq                            0.131         0.260 *       0.198        0.069        0.072       0.298 **     0.276 **   0.335 ** 
CRmeanNonzeroCS              -20.741       -80.533       -48.278      725.652      504.520     351.814 *   -197.516     -6.990    
Age0                          -0.034        -0.361         0.153        2.284        1.457       1.020       -0.657     -0.022    
SexMen                        -1.838        -9.893       -16.747       16.900       21.959       3.665      -25.231     -0.341    
RaceAfrAm                     -7.098        10.394        14.288       22.136        0.772      20.435      -32.895      0.614    
PovStatBelow                   8.054        18.470 *      23.768 *    -22.292      -32.774       1.833       32.121     -0.055    
CRmeanNonzeroCS:Age0           1.005         2.214         1.876      -12.803       -9.952      -6.430        5.286      0.218    
CRmeanNonzeroCS:SexMen        -4.110        62.847        82.573     -141.904     -126.558     -70.193      182.099      0.695    
CRmeanNonzeroCS:RaceAfrAm     37.237       -17.185       -48.072     -129.458      -53.648     -58.195      220.727     -3.340    
CRmeanNonzeroCS:PovStatBelow -51.687       -81.029 *    -130.617 *     71.738      126.737      -4.864     -203.870      1.768    


CRmeanLogLux -- Mean log illuminance exposure (circadian system activation)

                             BMI     BPsitRdia     BPsitRsys        Chol     LDLcalc         HDL     Glucose      CRPLS    
Rsq                        0.181         0.193         0.125       0.068       0.101       0.292 **    0.134      0.180    
CRmeanLogLux               2.254 *       0.083         1.070       4.691       5.146       0.653       4.290      0.021    
Age0                       0.376        -0.098         0.440       0.614       0.518       0.107       0.211      0.014    
SexMen                    -4.064         0.834        -2.130      -7.528       4.779     -13.379 *    13.801     -0.096    
RaceAfrAm                  2.830        11.558 *      16.295 *    21.805       6.267      14.980 *    15.023      0.013    
PovStatBelow               2.951         6.431         4.512     -16.401     -28.616      -0.651      -4.516      0.028    
CRmeanLogLux:Age0         -0.037         0.009        -0.002      -0.068      -0.088      -0.019      -0.056     -0.000    
CRmeanLogLux:SexMen        0.174         0.198         0.208      -0.255      -0.731       0.343      -0.042     -0.007    
CRmeanLogLux:RaceAfrAm    -0.493        -0.424        -1.035      -2.392      -1.596      -0.367      -1.313     -0.013    
CRmeanLogLux:PovStatBelow -0.547 *      -0.292        -0.462       0.639       1.940       0.204      -0.946      0.025    


CSphasorMag -- Phasor magnitude (circadian entrainment)

                             BMI     BPsitRdia     BPsitRsys        Chol     LDLcalc         HDL     Glucose      CRPLS    
Rsq                        0.099         0.265 *       0.194       0.088       0.101       0.309 **    0.208      0.174    
CSphasorMag              -29.105       -38.710        -7.239     559.009     573.533 *   211.093 *   200.717     -4.510    
Age0                      -0.080        -0.252         0.309       3.125       2.927       1.004       0.322     -0.009    
SexMen                     4.946       -16.052 *     -19.561       9.469      10.532     -14.174      13.773     -0.167    
RaceAfrAm                -10.480        15.794        25.834      13.863       1.700      28.172 *     1.172     -0.205    
PovStatBelow              -7.540        17.546 *      26.522 *    -7.400     -17.039      18.166       1.639     -0.212    
CSphasorMag:Age0           0.436         0.955         0.623     -11.017     -11.455 *    -3.727      -2.049      0.082    
CSphasorMag:SexMen       -19.167        64.739 *      57.525     -79.099     -49.896       7.180      23.859      0.098    
CSphasorMag:RaceAfrAm     37.611       -31.392       -76.944     -52.073     -30.692     -63.251      24.227      0.446    
CSphasorMag:PovStatBelow  20.549       -50.451       -95.610 *    -6.245      25.322     -59.415     -54.032      1.689    


CSphasorAngleHrs -- Phasor angle (night-owl: positive; lark: negative)

                                 BMI     BPsitRdia     BPsitRsys        Chol     LDLcalc         HDL     Glucose      CRPLS    
Rsq                            0.077         0.259 *       0.178       0.078       0.073       0.304 **    0.243 *    0.265 *  
CSphasorAngleHrs               0.509       -13.050 *     -15.886      -2.565       2.583      -3.193      -9.157     -0.065    
Age0                           0.050        -0.344         0.081       0.142      -0.077      -0.081      -0.424      0.012    
SexMen                        -0.727         1.132        -5.262     -30.066     -17.515     -11.534 *    -9.792     -0.231    
RaceAfrAm                      0.190        -1.151        -3.379       8.292       3.002       9.434      -2.197     -0.206    
PovStatBelow                  -2.803         2.302         3.110     -11.238      -8.813      -6.429      -6.280      0.714 ***
CSphasorAngleHrs:Age0          0.022         0.207         0.249      -0.069      -0.119      -0.015       0.165      0.001    
CSphasorAngleHrs:SexMen       -0.849         0.868         3.154      12.461       9.232       1.002      13.352 *    0.053    
CSphasorAngleHrs:RaceAfrAm    -0.485         5.277 **      6.309 *    -4.941      -6.921       1.424       4.305      0.060    
CSphasorAngleHrs:PovStatBelow -0.095         0.129        -2.182       2.241       0.430       5.307 *    -6.602     -0.249 ** 


CSinterdayStab -- Interday stability (day-by-day regularity of the activity-rest pattern)

                                BMI     BPsitRdia     BPsitRsys        Chol     LDLcalc         HDL     Glucose      CRPLS    
Rsq                           0.112         0.238 *       0.129       0.060       0.101       0.249 *     0.170      0.174    
CSinterdayStab               16.586       -59.073       -88.510     236.750     326.477      -9.795      64.683     -0.102    
Age0                          0.208        -0.384        -0.175       2.816       3.107       0.114       0.046      0.017    
SexMen                       10.499       -19.977       -13.928      13.185      18.310     -19.207      27.339     -0.103    
RaceAfrAm                   -11.697         2.735         3.560       6.202      12.887      12.736     -24.526     -0.260    
PovStatBelow                -10.300        12.932         5.077      -4.851      25.837       6.784     -28.121     -0.626    
CSinterdayStab:Age0          -0.353         0.717         1.231      -4.680      -5.758      -0.139      -0.875     -0.007    
CSinterdayStab:SexMen       -18.392        38.561 *      20.122     -46.188     -47.024      13.048      -6.081      0.009    
CSinterdayStab:RaceAfrAm     20.434         7.910         3.210     -14.720     -43.281      -3.602      58.385      0.342    
CSinterdayStab:PovStatBelow  14.083       -14.782        -6.992      -7.662     -64.295      -7.603      25.719      1.541    


CSintradayVar -- Intradaily variability (fragmentation of rhythm frequency)

                              BMI     BPsitRdia     BPsitRsys         Chol      LDLcalc         HDL     Glucose      CRPLS    
Rsq                         0.067         0.221 *       0.211        0.125        0.136       0.262 *     0.157      0.166    
CSintradayVar              23.931         2.562       -20.588     -318.798     -391.233 *   -58.672      54.616      0.694    
Age0                        0.239         0.085         0.696       -2.672       -3.851      -0.501       1.550      0.026    
SexMen                     -4.813        11.754       -16.337      -38.328      -18.103     -18.855      -9.269     -0.390    
RaceAfrAm                   3.412        -0.744       -16.484      -29.731      -41.361      11.564       9.564     -0.165    
PovStatBelow                0.038       -13.669       -31.086 *    -87.879 *    -63.136     -12.083     -55.860      0.698    
CSintradayVar:Age0         -0.343        -0.239        -0.582        4.555        6.245       0.800      -3.137     -0.020    
CSintradayVar:SexMen        5.243       -16.023        29.049       50.926       27.413      17.197      50.189      0.406    
CSintradayVar:RaceAfrAm    -7.377        14.405        40.404       49.073       58.142      -0.788      -6.568      0.121    
CSintradayVar:PovStatBelow -4.043        31.006        58.573 *    144.530 *     95.050      25.955      78.979     -0.773    

Ludwig Sleep Questionnaire

We also collected data on sleep with the Ludwig Sleep Questionnaire.

Here are descriptive statistics:

LMworkRegSch:    Regular work schedule
LMworkDays:      # days/week worked
LMworkAsleep:    Work day: minutes to sleep
LMworkAlarm:     Work day: use alarm clock
LMworkGetup:     Work day: minutes until get up
LMfreeAsleep:    Free day: minutes to sleep
LMfreeAlarm:     Free day: use alarm clock
LMfreeGetup:     Free day: minutes until get up
Sleepdurwork:    Work day: Time trying to sleep
Sleepdurfree:    Free day: Time trying to sleep
LMworkDaylight:  Work day: minutes spent outdoors in daylight
LMfreeDaylight:  Free day: minutes spent outdoors in daylight
 LMworkRegSch   LMworkDays        LMworkAsleep   LMworkAlarm  LMworkGetup        LMfreeAsleep      LMfreeAlarm  LMfreeGetup     Sleepdurwork        Sleepdurfree       LMworkDaylight    
 No :43       Min.   :3.000000   Min.   : 0.00   No  :14     Min.   : 0.00000   Min.   : 3.00000   No :66      Min.   : 2.00   Min.   : 2.500000   Min.   : 2.833333   Min.   : 10.0000  
 Yes:37       1st Qu.:4.000000   1st Qu.:10.00   Yes :24     1st Qu.: 5.00000   1st Qu.:10.00000   Yes:14      1st Qu.: 5.00   1st Qu.: 6.000000   1st Qu.: 5.750000   1st Qu.: 82.5000  
              Median :5.000000   Median :20.00   NA's:42     Median :10.00000   Median :20.00000               Median :10.00   Median : 7.000000   Median : 7.000000   Median :180.0000  
              Mean   :4.675676   Mean   :24.75               Mean   :12.91429   Mean   :27.02564               Mean   :23.08   Mean   : 6.912393   Mean   : 8.339827   Mean   :226.9444  
              3rd Qu.:5.000000   3rd Qu.:30.00               3rd Qu.:20.00000   3rd Qu.:30.00000               3rd Qu.:30.00   3rd Qu.: 7.750000   3rd Qu.: 9.000000   3rd Qu.:315.0000  
              Max.   :7.000000   Max.   :60.00               Max.   :30.00000   Max.   :90.00000               Max.   :99.00   Max.   :15.750000   Max.   :24.000000   Max.   :780.0000  
              NA's   :43         NA's   :40                  NA's   :45         NA's   :2                      NA's   :5       NA's   :41          NA's   :3           NA's   :44        
 LMfreeDaylight    
 Min.   : 10.0000  
 1st Qu.:120.0000  
 Median :240.0000  
 Mean   :229.7973  
 3rd Qu.:300.0000  
 Max.   :600.0000  
 NA's   :6         
   LMworkBed         LMworkReady        LMworkAwake         LMfreeBed         LMfreeReady        LMfreeAwake      
 Min.   :00:00:00   Min.   :00:00:00   Min.   :00:00:12   Min.   :00:00:00   Min.   :00:00:00   Min.   :00:00:00  
 1st Qu.:01:30:00   1st Qu.:01:05:00   1st Qu.:05:00:00   1st Qu.:01:00:00   1st Qu.:00:37:30   1st Qu.:05:00:00  
 Median :20:30:00   Median :17:37:30   Median :06:00:00   Median :21:00:00   Median :11:52:30   Median :06:30:00  
 Mean   :14:13:11   Mean   :12:34:23   Mean   :06:42:45   Mean   :14:31:53   Mean   :11:44:02   Mean   :06:29:56  
 3rd Qu.:22:30:00   3rd Qu.:22:15:00   3rd Qu.:07:18:45   3rd Qu.:22:30:00   3rd Qu.:22:30:00   3rd Qu.:08:00:00  
 Max.   :23:30:00   Max.   :23:45:00   Max.   :20:30:00   Max.   :23:30:00   Max.   :23:35:00   Max.   :12:00:00  
 NA's   :39         NA's   :40         NA's   :40                            NA's   :2          NA's   :1         

Pittsburgh Sleep Quality Inventory

We administered the Pittsburgh Sleep Quality Inventory (PSQI) as part of the overall HANDLS protocol.

PSQI generates an overall sleep quality score (PSQglobal) and a cut-off indicating sleep quality problems (PSQproblem).

   PSQglobal         PSQproblem
 Min.   : 0.000000   No  :21   
 1st Qu.: 4.000000   Yes :27   
 Median : 6.000000   NA's:32   
 Mean   : 7.041667             
 3rd Qu.:10.000000             
 Max.   :16.000000             
 NA's   :32                    

plot of chunk descPSQI

Regrettably, we have missing data on the PSQI. Of the 80 participants for whom we have phaser data, we have only 48 who completed the PSQI.

Nevertheless, it may be useful to examine the relationship of sleep quality with phasor magnitude for which we expect at least a moderate correlation. Per below, it appears as though sleep quality assessed by the PSQI and phasor magnitude are unrelated in HANDLS.

            PSQglobal CSphasorMag
PSQglobal    1.00     -0.07      
CSphasorMag -0.07      1.00      

n
            PSQglobal CSphasorMag
PSQglobal          48          48
CSphasorMag        48          80

By visual inspection, there isn't much difference in phasor magnitude by sleep quality problems.

plot of chunk boxPSQI

In addition, neither PSQI overall sleep quality (PSQglobal) nor sleep quality problems (PSQproblem) are related to phasor magnitude after adjusting for sex, race, and poverty status.


Call:
glm(formula = CSphasorMag ~ Sex + Race * PovStat + PSQglobal, 
    data = w03Circadian)

Deviance Residuals: 
        Min           1Q       Median           3Q          Max  
-0.20741138  -0.04102181   0.01036750   0.06083752   0.14826409  

Coefficients:
                            Estimate    Std. Error  t value          Pr(>|t|)
(Intercept)             0.3446272686  0.0386673779  8.91261 0.000000000031036
SexMen                 -0.0623245271  0.0247884544 -2.51426          0.015847
RaceAfrAm              -0.0398965877  0.0326940477 -1.22030          0.229158
PovStatBelow            0.0249715567  0.0372860713  0.66973          0.506696
PSQglobal              -0.0008563959  0.0034095406 -0.25118          0.802903
RaceAfrAm:PovStatBelow -0.0366631144  0.0500785076 -0.73211          0.468166

(Dispersion parameter for gaussian family taken to be 0.006538276337)

    Null deviance: 0.34986831  on 47  degrees of freedom
Residual deviance: 0.27460761  on 42  degrees of freedom
  (32 observations deleted due to missingness)
AIC: -97.63533

Number of Fisher Scoring iterations: 2

Call:
glm(formula = CSphasorMag ~ Sex + Race * PovStat + PSQproblem, 
    data = w03Circadian)

Deviance Residuals: 
         Min            1Q        Median            3Q           Max  
-0.203137411  -0.044140898   0.009680942   0.060637207   0.152982971  

Coefficients:
                          Estimate  Std. Error  t value   Pr(>|t|)
(Intercept)             0.34415542  0.03188729 10.79287 1.0953e-13
SexMen                 -0.06187962  0.02449303 -2.52642    0.01538
RaceAfrAm              -0.03997323  0.03194843 -1.25118    0.21779
PovStatBelow            0.02432728  0.03727306  0.65268    0.51752
PSQproblemYes          -0.01016516  0.02449303 -0.41502    0.68024
RaceAfrAm:PovStatBelow -0.03521726  0.05003347 -0.70387    0.48540

(Dispersion parameter for gaussian family taken to be 0.00652135337)

    Null deviance: 0.34986831  on 47  degrees of freedom
Residual deviance: 0.27389684  on 42  degrees of freedom
  (32 observations deleted due to missingness)
AIC: -97.759729

Number of Fisher Scoring iterations: 2

Where shall we go from here?