Table 2

 Age distribution, occupational exposure to airborne agents and educational level of the four populations

Population A(n = 2358)Population B(n = 1184)Population C(n = 539)Population D(n = 331)
Values are number (%) unless otherwise indicated.
Population A: parent population; population B: those without the cardinal respiratory symptoms of breathlessness, cough and wheeze; population C: never-smokers without the cardinal respiratory symptoms of breathlessness, cough and wheeze; population D: never-smokers without any respiratory symptoms.
Men 1142 (48)595 (50)242 (45)154 (47)
Mean (SD) age (years)49.1 (14.4)48.1 (13.8)45.2 (13.2)46.3 (13.9)
Age 26–39350 (30)189 (32)100 (41)61 (40)
Age 40–49294 (26)160 (27)65 (27)36 (23)
Age 50–59203 (18)116 (19)36 (15)27 (18)
Age 60–69160 (14)77 (13)28 (12)19 (12)
Age 70–82135 (12)53 (9)13 (5)11 (7)
Occupational exposure
    Yes706 (63)326 (56)109 (46)64 (43)
Educational level
    Primary192 (17)74 (13)15 (6)11 (7)
    Secondary654 (58)332 (56)117 (49)74 (49)
    University283 (25)183 (31)107 (45)66 (44)
Women 1216 (52)589 (50)297 (55)177 (53)
Mean (SD) age (years)50.5 (15.1)48.1 (14.2)50.9 (15.4)52.5 (14.9)
Age 26–39335 (28)177 (30)77 (26)37 (21)
Age 40–49300 (25)163 (28)70 (24)43 (24)
Age 50–59234 (19)127 (22)66 (22)42 (24)
Age 60–69165 (13)61 (10)35 (12)24 (14)
Age 70–82182 (15)61 (10)49 (16)31 (17)
Occupational exposure:
    Yes374 (32)142 (25)66 (23)39 (23)
Educational level
    Primary229 (19)93 (16)46 (16)28 (16)
    Secondary705 (59)326 (56)156 (54)94 (54)
    University263 (22)162 (28)89 (30)51 (30)