Results
One hundred thirty-three adolescents with asthma remission, who had both natural parents, were enrolled in this study. Of the parents, three pairs of parents themselves declined to participate in the study, and one member of four pairs could not perform the test due to a poor technique of forced expiratory maneuver or due to a lower FEV1 level. Complete data were therefore available for 126 adolescents and their parents (Table 1).
The clinical characteristics of the BHR-positive and BHR-negative adolescents were compared in Table 2. No differences were observed between BHR-positive and BHR-negative adolescents, with respect to age, sex, age of asthma onset, history of prophylactic medications, duration of asthma remission, atopic status as assessed by total serum IgE and the pattern of positive skin responses, environmental factors, or the FEV1.
Comparison of BR in Parents Categorized by the Presence or Absence of Persisting BHR in Adolescents
Figure 1 compares the BR index and the frequency of BHR between the parents of BHR-positive adolescents and the parents of BHR-negative adolescents. The parents (n = 138) of the BHR-positive adolescents had a BR index of 1.150 ± 0.103 (fathers, 1.144 ± 0.100; mothers, 1.156 ± 0.106). This was statistically different (p = 0.029) from the value (1.124 ± 0.088) [fathers, 1.117 ± 0.091; mothers, 1.131 ± 0.086] obtained from the parents (n = 114) of the BHR-negative adolescents. The frequency of BHR in the parents of the BHR-positive adolescents was 28.3% (39 of 138 parents) [18 of 69 fathers; 21 of 69 mothers], compared to 16.7% (19 of 114 parents) [9 of 57 fathers; 10 of 57 mothers] in the parents of the BHR-negative adolescents (p = 0.030).
Table 1—Characteristics of Adolescents and Their Parents Completing the Study *
| Parents | |||
| Characteristics | Adolescents | 1
Fathers |
1
Mothers |
| Cases | 126 | 126 | 126 |
| Age, yr | 14.9 ± 1.1 | 44.7 ± 4.2 | 42.0 ± 4.1 |
| Male/female sex | 88/38 | ||
| BHRt | 69 | 27 | 31 |
| BR index | 1.222 ± 0.087 | 1.132 ± 0.096 | 1.145 ± 0.098 |
| Current smokers in | 69 | 3 | |
| household | |||
| Doctor-diagnosed | 10 | 12 | |
| asthma | |||
*Data are presented as No. or mean ± 1 SD.
TPC20 < 18 mg/mL.
Comparison of BR in Adolescents Categorized by the Presence or Absence of BHR in Parents
Figure 2 shows the PC20 and the BR index of adolescents categorized on the basis of whether or not their parents have BHR. Two adolescents had both BHR-positive parents, 54 had one BHR-posi-tive parent, and 70 had both BHR-negative parents. Thirteen of 56 adolescents with at least one BHR-positive parent and 33 of 70 adolescents with BHR-negative parents had immeasurable PC20 (> 25 mg/ mL).