Background
Methods
Subjects
Social and demographic variables
Therapeutic regimen
Pulmonary function
Actual function
Best function
Measurement
Ethical approval
Statistical analysis
Results
General
Male | Female | ||
---|---|---|---|
n | 457 | 455 | |
Age (years)(sd) | 50.4(15.4) | 49.3(16.3) | |
Duration of asthma (years)(sd) | 17.0(16.2) | 18.6(15.4) | |
Atopic n(%) | 258(56.5) | 227(49.9) | |
Asthma n(%) | childhood | 124(27.1) | 131(28.8) |
gap | 53(11.6) | 42(9.2) | |
adult | 280(61.3) | 282(63.3) | |
Social Class n(%) | 1–2 | 131(28.8) | 139(30.5) |
3 | 168(36.9) | 180(39.6) | |
4–5 | 156(34.3) | 136(29.9) | |
Smoking Habit n(%) | never | 147(32.2) | 247(54.3) |
ever | 239(52.3) | 161(35.4) | |
current | 71(15.5) | 47(10.3) | |
Pulmonary Function(sd) | Actual FEV1 l. | 2.50(1.09) | 1.97(0.79) |
Best FEV1 l. | 2.60(1.08) | 2.08(0.82) | |
Best FVC l. | 4.17(1.25) | 3.05(0.84) | |
Best PEF l/min | 465.7(113.7) | 382.0(85.1) | |
Actual/Best PEF % | 84.4(13.7) | 83.2(15.9) |
Change in function
Annual Decline | n | Actual FEV1 l. | Best FEV1 l. | Best FVC l. | ||
---|---|---|---|---|---|---|
Males |
Over 5 Years
|
All Subjects
| 776 | 41.0 (34.7–47.3) | 42.9 (37.5–48.3) | 63.1 (55.7–71.2) |
Never smokers
| 256 | 34.2 (22.2–46.2) | 33.4 (22.7–44.1) | 49.2 (35.6–62.8) | ||
Over 15 Years
| 85 | 46.7 (38.7–54.7) | - | 64.7 (54.6–74.8) | ||
Females |
Over 5 Years
|
All Subjects
| 848 | 28.9 (23.2–34.6) | 34.4 (29.8–39.0) | 45.8 (40.0–51.6) |
Never smokers
| 375 | 28.7 (22.4–38.8) | 30.6 (22.2–35.2) | 45.2 (36.4–54.0) | ||
Over 15 Years
| 115 | 24.7 (14.8–31.2) | - | 44.6 (37.9–51.3) |
Associations with entry variables
All subjects: 5-year intervals
Univariate analysis
Actual FEV1 | Best FEV1 | Best FVC | |||||
---|---|---|---|---|---|---|---|
Estimate | 95% CI | Estimate | 95% CI | Estimate | 95% CI | ||
Gender (male v female) | 7.7 | 0.8+,16.1 | 6.2 | 2.5+,14.9 |
12.2
|
2.5,21.9
| |
Age at entry (per decade) (difference from age 50) | Linear | 5.6+
| 11.4+,0.2 |
10.1
+
|
15.9
+,4.8
+
| 2.1+
| 8.7+,4.5 |
quadratic |
4.3
+
|
6.0
+,2.5
+
|
5.0
+
|
6.8
+,3.3
+
|
4.5
+
|
6.5
+,2.6
+
| |
cubic |
1.3
|
0.3,2.3
|
2.0
|
1.0,2.9
|
1.4
|
0.3,2.6
| |
Duration of asthma at entry (per decade) (difference from duration 20 yrs) | Linear | 3.1+
| 7.4+,1.1 | 0.5 | 3.8+,4.8 | 0.1 | 4.8+,5.0 |
quadratic |
3.6
|
0.6,6.6
| 2.7 | 0.5+,5.8 |
5.6
|
2.2,9.0
| |
cubic |
0.9
+
|
1.6
+,0.1
+
|
0.9
+
|
1.7
+,0.1
+
|
1.4
+
|
2.3
+,0.6
+
| |
Atopic | 5.7+
| 14.2+,2.8 | 0.2 | 8.5+,8.9 | 3.0+
| 12.7+,6.7 | |
Childhood asthma (versus no childhood asthma) | Gap | 3.4+
| 16.7+,9.9 | 1.4 | 12.2+,15.0 | 4.0+
| 19.4+,11.3 |
Yes |
20.8
+
|
30.6
+,10.9
+
|
10.6
+
|
20.9
+,0.4
+
|
22.0
+
|
33.3
+,10.6
+
| |
Social Class (versus classes 1 and 2) | Three | 6.3+
| 16.5+,3.8 |
11.2
+
|
21.7
+,0.8
+
| 9.2+
| 20.8+,2.3 |
Four and Five | 10.2+
| 21.0+,0.7 |
14.5
+
|
25.6
+,8.3
+
| 8.6+
| 21.0+,3.9 | |
Amount smoked (per 10 pack years) | 1.5 | 0.6+,3.7 | 0.2 | 2.1+,2.4 |
2.9
|
0.4,5.4
| |
Best PEF(per 10% deficit) |
3.3
+
|
5.3
+,1.2
+
|
2.8
+
|
4.8
+,0.7
+
| 0.4+
| 2.7+,2.0 | |
Actual/Best PEF(10% deficit) |
12.7
+
|
15.6
+,9.8
+
| 2.8+
| 6.2+,0.6 | 0.6+
| 4.1+,2.8 |
Multivariate analysis
Age Excluded | Age Included | ||||
---|---|---|---|---|---|
Coefficient | p | Coefficient | p | ||
Gender (male v female) | 5.5 (4.8) | 0.25 | 5.7 (4.7) | 0.23 | |
Asthma since childhood |
13.5
+
(5.1)
|
0.008
| 4.9+ (5.8) | 0.40 | |
Social Classes 1 & 2 (v. classes 4 & 5) | 4.8 (5.4) | 0.65 | 1.8 (5.4) | 0.88 | |
Social Class 3 (v. classes 4 & 5) | 1.1 (5.1) | 0.6+ (5.0) | |||
Amount smoked (per 10 pack years) | 1.8 (1.2) | 0.13 | 1.0 (1.2) | 0.39 | |
Best PEF(per 10% deficit) | 1.2+ (1.2) | 0.33 | 0.9+ (1.2) | 0.41 | |
Actual/Best PEF(10% deficit) |
12.0
+
(1.6)
|
<0.0001
|
13.2
+
(1.6)
|
<0.0001
| |
Age at entry (per decade) (difference from age 50) | Linear | 3.5+ (3.1) | |||
quadratic | 4.9+ (0.9) | ||||
cubic |
1.2 (0.6)
|
0.02
| |||
Duration of asthma at entry (per decade) (difference from duration 20 yrs) | Linear | 1.3 (2.8) | 2.0+ (2.4) | ||
quadratic | 3.2 (1.5) | 0.9 (0.5) | |||
cubic |
0.85
+
(0.38)
|
0.03
| 2.5+ (0.39) | 0.52 |
Age Excluded | Age Included | ||||
---|---|---|---|---|---|
Coefficient (sd) | p | Coefficient (sd) | p | ||
Gender (male v female) |
11.3 (5.1)
|
0.03
|
11.9 (5.4)
|
0.02
| |
Asthma since childhood | 5.1+ (5.3) | 0.34 | 1.1+ (6.0) | 0.86 | |
Social Classes 1 & 2 (v. classes 4 & 5) |
13. (5.7)
|
0.05
| 10.7 (5.6) | 0.11 | |
Social Class 3 (v. classes 4 & 5) |
2.9 (5.3)
| 1.4 (5.2) | |||
Amount smoked (per 10 pack years) | 0.7 (1.3) | 0.60 | 0.5 (1.3) | 0.71 | |
Best PEF(per 10% deficit) |
3.4
+
(1.3)
|
0.008
|
3.1
+
(1,2)
|
0.01
| |
Actual/Best PEF(10% deficit) | 0.7+ (1.8) | 0.71 | 1.4+ (1.8) | 0.44 | |
Age at entry (per decade) (difference from age 50) | Linear | 8.4+(3.2) | |||
quadratic | 5.1+ (0.9) | ||||
cubic |
1.8 (0.5)
|
0.0003
| |||
Duration of asthma at entry (per decade) (difference from duration 20 yrs) | Linear | 3.1 (2.4) | 0.2 (2.4) | ||
quadratic | 2.5 (1.6) | 0.4 (1.6) | |||
cubic |
0.91
+
(0.39)
|
0.02
| 0.29+ (0.40) | 0.46 |
Age Excluded | Age Included | ||||
---|---|---|---|---|---|
Coefficient (sd) | p | Coefficient (sd) | p | ||
Gender (male v female) |
10.8 (5.6)
|
0.05
|
11.4 (5.6)
|
0.04
| |
Asthma since childhood |
16.0
+
(6.0)
|
0.007
| 4.7+ (6.9) | 0.49 | |
Social Classes 1 & 2 (v. classes 4 & 5) | 10.7 (6.4) | 0.13 | 7.5 (6.4) | 0.29 | |
Social Class 3 (v. classes 4 & 5) | 0.2+ (6.0) | 1.4+ (5.9) | |||
Amount smoked (per 10 pack years) | 1.9 (1.4) | 0.18 | 0.9 (1.4) | 0.52 | |
Best PEF(per 10% deficit) | 0.6+ (1,.4) | 0.65 | 0.6+ (1.9) | 0.67 | |
Actual/Best PEF(10% deficit) | 1.3 (1.8) | 0.47 | 0.1 (1.9) | 0.94 | |
Age at entry (per decade) (difference from age 50) | Linear | 2.1+ (3.7) | |||
quadratic | 4.0+ (1.0) | ||||
cubic |
1.4 (0.6)
|
0.02
| |||
Duration of asthma at entry (per decade) (difference from duration 20 yrs) | Linear | 4.0 (2.8) | 0.8 (2.8) | ||
quadratic | 5.2 (1.7) | 3.2 (1.8) | |||
cubic |
1.46
+
(0.44)
|
0.001
|
0.97
+
(0.46)
|
0.03
|