Table 4 Ordinal logistic regression for association between socioeconomic status (SES) and headache impact (HIT-6). Addition of interaction “SES * physical activity” to Model 4. Weighted random sample

SES (ref. = high)

 Low SES

1.158**

.436

0.30, 2.01

 Medium SES

.382

.296

-0.20, 0.96

Other Sociodemographic variables

 Sex (ref. = men)

.578***

.157

0.27, 0.89

 Age

-.005

.006

-0.02, 0.01

 Marital status (ref. = married)

  Unmarried

.105

.260

-0.40, 0.61

  Divorced

-.056

.279

-0.60, 0.49

  Widowed

-.468

.365

-1.19, 0.25

 Living without partner (ref. = living with partner)

-.053

.238

-0.52, 0.41

 Children < 18 years (ref. = no)

.096

.191

-0.28, 0.47

 Living in a rural area (ref. = living in an urban area)

.150

.214

-0.27, 0.57

Headache-related variables

 Analgesic use (days a month)

.086***

.016

0.05, 0.12

 Headache duration (in years)

.001

.007

-0.01, 0.01

 Headache frequency (ref. = less than 4 days a month)

  4–14 days a month

1.213***

.210

0.80, 1.62

  > 14 days a month

.650

.443

-0.22, 1.52

 Migraine (ref. = no)

1.479***

.182

1.12, 1.83

Other health variables

 Physical inactivity (ref. = physical active persons)

.484

.331

-0.17, 1.13

 Obesity (BMI ≥ 30) (ref. = no obesity)

.184

.185

-0.18, 0.54

 Depressive symptoms (PHQ) (ref. = no depressive symptoms)

.626**

.234

0.17, 1.08

Interaction

 SES * Physical inactivity

  Low SES: physical inactivity (ref. = physical active persons)

-.794

.521

-1.81, 0.23

  Medium SES: physical inactivity (ref. = physical active persons)

-.241

.387

-1.00, 0.52

 Model fitting: χ² (df)

247.66 (20) ***

 Goodness of fit

  (Pearson) χ² (df)

2187.42 (2248)

 (Deviance) χ² (df)

1650.84 (2248)

 Pseudo-R² (Nagelkerke`s)

.338

 Test of proportional odds: χ² (df)

48.92 (40)