Table 1

Health condition (physician-diagnosed) by sampling frame among 2,061 subjects identified by random digit dialling

National n (%)“Hot spots” n (%)“Condition” n (%)Total n (%)
Subjects n9799761062061
Any chronic airway disease190 (19)210 (22)106 (100)506 (25)
COPD135 (14)163 (17)79 (75)377 (18)
Emphysema54 (6)57 (6)33 (31)144 (7)
Chronic bronchitis105 (11)130 (13)53 (50)288 (14)
COPD with concomitant asthma53 (5)54 (6)33 (31)140 (7)
Asthma without COPD55 (6)47 (5)27 (25)129 (6)
No chronic airway disease789 (81)766 (78)1555 (75)
  • Specific health conditions are not mutually exclusive, except as indicated for asthma

  • The national sample was derived by random digit dialling within continental USA

  • The “hot spots” sample was derived by random digit dialling within higher incidence areas for chronic obstructive pulmonary disease (COPD) based on US mortality data

  • The “condition” sample was derived from further random digit dialling in the hot spot areas, limiting eligibility to subjects reporting at least one of the target conditions (see Sampling frames and recruitment section)