Table 1 Candidate predictors and their characteristics

From: Prediction of COPD-specific health-related quality of life in primary care COPD patients: a prospective cohort study

Candidate predictors

Coding

p5, p50, p95

No. of missings out of 409 (%)

Sex a

1=male, 2=female

57

0 (0)

Age

Continuous (years)

52, 67, 83

0 (0)

Body mass index

Continuous (kg/m2)

19, 25, 35

0 (0)

Living situation a

1=single, 2=partner/children

36

2 (0.5)

Smoking status b

1=smoker, 2=former smoker, 3=never smoker

41, 54, 5

1 (0.2)

Cough a

0=no, 1=yes

49

0 (0)

Phlegm a

0=no, 1=yes

48

3 (0.7)

Exacerbations

 At home

Count

0, 0, 1

0 (0)

 In hospital

Count

0, 0, 0

0 (0)

Medication a

 Anxiolytics

0=no, 1=yes

14

0 (0)

 Antidepressants

0=no, 1=yes

11

0 (0)

 Cardiovascular

0=no, 1=yes

65

0 (0)

 Pulmonary

0=no, 1=yes

82

0 (0)

Long-acting beta-agonists b

0=no, 1=yes

59

0 (0)

Inhaled corticosteroids b

0=no, 1=yes

60

0 (0)

Vaccination a

 Influenza

0=no, 1=yes

78

1 (0.2)

 Pneumococcal

0=no, 1=yes

7

1 (0.2)

 Physical activity a

0=no, 1=yes

24

0 (0)

Comorbidity: a

 Cardiovascular

0=no, 1=yes

20

0 (0)

 Neurological

0=no, 1=yes

9

0 (0)

 Renal

0=no, 1=yes

19

0 (0)

 Diabetes mellitus

0=no, 1=yes

15

0 (0)

 Musculoskeletal

0=no, 1=yes

29

0 (0)

 Psychiatric

0=no, 1=yes

19

0 (0)

Lung function (FEV1% of predicted)

Continuous (%)

25, 59, 78

0 (0)

Feeling thermometer

Continuous (0–100)

45, 70, 95

1 (0.2)

HRQL: 4 CRQ domains

Continuous (1–7)

  

 Dyspnoea

 

2.2, 4.8, 7.0

0 (0)

 Fatigue

 

2.0, 4.5, 6.5

0 (0)

 Emotional function

 

2.7, 5.4, 6.7

0 (0)

 Mastery

 

3.3, 5.8, 7.0

0 (0)

Depression score (HADS)

Continuous (0–21)

1, 5, 11

0 (0)

Physical activity score (LAPAQ)

Continuous (0–7)

1, 4, 6

0 (0)

Self-efficacy, 3 questions

Continuous (1–5)

  

SEI 1 (illness-related)

 

2, 4, 5

1 (0.2)

SEI 2 (dyspnoea-related)

 

1, 4, 5

2 (0.5)

SEI 3 (medication-related)

 

1, 5, 5

30 (7.3)

Handgrip test, best of 6 attempts

Continuous (kg)

18, 34, 56

0 (0)

Sit to stand test

Count (repetitions/min)

0, 17, 37

0 (0)

  1. Abbreviations: CRQ, chronic respiratory questionnaire; FEV1, forced expiratory volume in 1 s, HADS, Hospital Anxiety and Depression Scale; HRQL, health-related quality of life; LAPAQ, LASA (Longitudinal Ageing Study Amsterdam) Physical Activity Questionnaire; p5, 5th centile; p50, median; p95, 95th centile.
  2. aFor binary variables, the number in the third column is the percentage of patients with code 1, for example, 57% is male and 49% has a cough.
  3. bFor this categorical variable, the numbers in the third column are the percentages of patients with code 1, 2 and 3, respectively, for example, 41% is a smoker.
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