EUROPEAN
Eur. J. Epidemiol. 0392-2990
Vol. 8, No. 5
JOURNAL
September 1992, p. 733-736
OF EPIDEMIOLOGY
H E R E D I T Y OF ASTHMA IN SAUDI POPULATION A. BENER .1, T.Q. AL-JAWADI**, M. SIMSEK*** and K.E. AL-NASSAR*** *Dept. o f Community Medicine - Faculty o f Medicine and Health Sciences United Arab Emirates University - P.O. B o x 1 7 6 6 6 - A l Ain - UNITED A R A B EMIRATES. **Dept. o f Paediatrics - College o f Medicine & K A A UH - King Abdulaziz University P.O. B o x 9025 - Jeddah 21413 - SA UDI A R A B I A . ***Department o f Biochemistry - Faculty o f Medicine - Kuwait University P.O. B o x 24923 - Safat-13110 - S T A T E OF K U W A I T .
Key words: Heredity - Asthma - Hay fever - Eczema - Parent - Child - Saudi population In a cross-sectional study, the prevalence of asthma, hay fever and eczema was studied in 1150 schoolchildren attending school in Jeddah Western region of Saudi Arabia. The family histories of asthma, hay fever and eczema were examined in first degree relatives. The age range of children studied was 7-12 years, with a mean of 9.3 years (470/0 boys and 530/0 girls;). A self-administered questionnaire was completed by the parents of the child to collect information concerning bronchial asthma, hay fever, and eczema in the target child and family history of respiratory allergy. A detailed family history and personal histories of asthma were available for 1035 Saudi children aged 7-12 years old. The rate of asthma and hay fever were significantly higher among siblings and offspring (cases) compared to their parents (p < 0.001). The results showed a high positive correlation between the relatives of affected children with respect to asthma and hay fever. These findings support the hypothesis that asthma and hay fever may be inherited in the Saudi population, but the mode of inheritance has yet to be determined.
INTRODUCTION
Heredity has long been considered to influence allergic disorders, particularly bronchial asthma. A genetic component in the etiology of certain allergic diseases has been generally accepted (5). Drinkwater (4) suggested that asthma is inherited as a single Mendelian dominant character. On the contrary, Adkinson (1) thought the disease to be a simple recessive trait. Later, Schnyder (17) concluded that the disease was inherited by a single autosomal dominant gene with reduced penetrance. But Leigh and Marley (12) considered that a multifactorial type of inheritance was more probable. The studies showed that hereditary asthma can best be explained by multiple gene inheritance (18). This type of inheritance, however, cannot be clearly 1 Corresponding author.
distinguished from single dominant gene inheritance in common disorders (3). The strong similarities between asthmatic and wheezy bronchitic children in their family histories of asthma and wheezy bronchitis suggest that these two forms of illness share a common genetic defect (19, 20). Most family studies provide a considerable genetic component, with positive family histories in 48-74 per cent of the cases (1, 21). The overall prevalence of asthma in first degree relatives of asthmatics was significantly higher than in the relatives of normal controls (20, 21, 6). Genetic mechanisms have been proposed to explain the presence of asthma in families (11). The prevalence of asthma was found to be even higher among twins examined (8, 22). Longo et al. (12) suggest that bronchial hyperactivity is an autosomal dominant trait with incomplete penetrance and is present in about 10% of the normal healthy population. Bronchial reactivity is inherent in all asthmatic (7).
733
Bener A. et al.
Eur. J. Epidemiol.
In Saudi Arabia, a few large, population-based studies have been conducted to define the important epidemiologic characteristics of allergic diseases amongst school age children. The aim of the present study was to investigate the hereditary of bronchial asthma, hay fever, and eczema among the Saudi population.
pair agreement. Agreement for the trait in question was valued one for each member of the pair, non-agreement was valued zero. In this study correlations were calculated for father-child, and for sib pairs of both like and unlike sex. RESULTS
MATERIALS AND METHODS
This cross-sectional, population-based study of bronchial asthma among schoolchildren aged 7-12 years was conducted in the city of Jeddah, western region of the Kingdom of Saudi Arabia. The field survey was conducted during the period January, 1986 February, 1989. Jeddah, with a population of 1.5 million, is located in the humid western coast of the country. One thousand one hundred and fifty school students aged 7-12 years were randomly selected in Jeddah city. A standardized questionnaire along with a letter of explanation was distributed among the selected students. The questionnaire was completed by the student's parents with the help of a nurse, senior medical student, allergist consultant and co-investigator. Information obtained from the respondents included: area of residence and social class of family; fathers occupation, mother's occupation; age, sex, history of asthma, hay fever and eczema in the target child; family history of respiratory allergy and parental smoking habits and parents daily cigarette consumption at home. Data were analyzed on the IBM computer of the College of Medicine at King Sand University. The SAS statistical package program was used to calculate the Chisquare values to assess the statistical significance of contingency table, SAS User Guide (15). The correlation was used to examine the relationships between asthmatic children and their parents. In the correlation method, the traits were classified into major categories of asthma, hay fever and eczema. Each parent-child pair in which either member showed the trait in question was examined for -
In Jeddah, a total of 1150 randomly selected students aged 7-12 years were provided with questionnaires to be completed by their parents. The parents of 1035 children (900/0) agreed to participate in the study. The age range of the children studied was 7-12 years, with a mean of 9.3 years; 470/0 were boys and 530/owere girls. The diagnosis of asthma and other allergic diseases from a questionnaire is often less exact than a physician's diagnosis. This data, however, includes many individuals that have been symptom-flee for many years since allergic symptoms become less frequent in older age groups. A physician's diagnosis would have to be based on the individual's own information about symptoms earlier in life rather than actual findings, and therefore would be similar to a questionnair diagnosis. One attempt has been made at estimating the reliability of the answers given by individuals. The validity of the questionnaire diagnosis was tested in 50 cases who were examined by an allergist at the King Abdulaziz University Hospital after they had returned the questionnaire. The consistency was high; only 90/0 had given inconsistent answers for bronchial asthma, only 13% had given inconsistent answers for hay fever and only 11.5% had given inconsistent answers for eczema. The distribution and comparison of asthma, hay fever and eczema among first degree relatives are shown in Table 1. The family history of asthma differed between asthmatic relatives. There were significantly more asthmatic siblings (15.3%) and offspring (16.2%) than asthmatic fathers (10.53%) and mothers (10.9%) (p < 0.001). The rate of asthma did not differ significantly between the siblings and offspring (p > 0.10). Similarly the prevalence rate of
TABLE 1. - The prevalence rate of asthma, hay fever and eczema among first degree relatives. RELATIVES Trait
Father
Mother
Siblings
Offspring (cases)
Significant differences*
Asthma
85 (10.5)
88 (10.9)
124 (15.3)
131 (16.2)
p < 0.001
Hay fever
51
(6.3)
35
(4.3)
105 (13.0)
202 (25.0)
p < 0.01
Eczema
36
(4.5)
48
(5.9)
37
(4.6)
62
(7.7)
p < 0.025
* = Chi-square test has been used for comparison of significant differences of father, mother, siblings and offspring.
734
Vol. 8, 1992
Asthma in Saudi Arabia
TABLE 2. - Correlation between relatives with respect to asthma, hay fever and eczema traits. RELATIVES Father-Child
Mother-Child
Sib-Sib
Traits
r(S.E.)
No. of pairs
r(S.E.)
No. of pairs
r(S.E.)
No. of pairs
Asthma
0.708 (0.104)
22
0.730 (0.09)
28
0.690 (0.062)
67
Hay fever
0.675 (0.109)
25
0.674 (0.120)
16
0.635 (0.070)
53
Eczema
0.709 (0.167)
8
0.721 (0.150)
11
0.689 (0.089)
35
hay fever did not differ between fathers (6.35%) and mothers (4.3%). But the prevalence rate of hay fever between siblings (130/0) and offspring (25%) were statistically significant (p < 0.001). Furthermore, the prevalence rate of eczema was higher in offspring (7.7%) than in siblings (4.6%), or fathers (4.5%) and mothers (5.9%). The increased rate of asthma, hay fever and eczema among siblings and offspring with fathers or mothers effected support the hypothesis that this trait is hereditary. Table 2 gives the correlation coefficient between first degree relatives. A comparison of the correlations in Table 2 among relatives, including father-child, mother-child and sib-sib showed a high positive correlation for the traits of asthma, hay fever and eczema (p < 0.001). The results of the present study could be interpreted as giving support to the hypothesis that bronchial asthma has an inherited component in Saudi children. DISCUSSION
The overall prevalence of asthma, hay fever and eczema were significantly higher between siblings and offspring than one parent (p < 0.001). The increased rate of asthma, hay fever and eczema among siblings and offspring with fathers and mothers affected, supports the hypothesis that asthma is inherited. It is generally agreed that the greater degree of inheritance leads to a greater likelihood of the offspring becoming sensitive. Furthermore, when both parents are affected the disease in the children appears earlier (10). Recently, Horwood et al. (9) showed very significant associations between the development of asthma and a large number of environmental, social and familial factors, including breast-feeding, parental smoking habits, pets in the child's family, stress in the family and family social background. A more recent
study (16) suggested that the environment in an inland town provides one or more additional risk factors for bronchial asthma in a study of two populations of Australian school children. It appears that the children in each town or city may have a different genetic expression for bronchial asthma due to different environmental exposures. In the present study, we showed that a higher prevalence of asthma in the humid coastal area and the child's family history play a significant role in the development of asthma. A1-Frayh et al. (2) reported that the prevalence rates of bronchial asthma, hay fever and eczema were higher in children than their fathers or mothers. A survey of bronchial asthma prevalence and inheritance patterns was carried out in the municipality of San Antonio, La Habana, Cuba by Rodriguez et al. (14). Their survey supported the hypothesis that the occurrence of bronchial asthma is strongly influenced by inheritance. Their results tend to confirm that the inheritance of bronchial asthma is autosomal and does conform to simple dominant or recessive inheritance patterns. Thus, a family history of allergy not only establishes predisposition but also determines the age at which the allergy will appear. Finally, strong similarities between asthmatic and wheezy bronchitic children in their family histories of asthma and wheezy bronchitis suggest that these two forms of illness share a common genetic defect (19, 20). Overall, our findings suggest that the particular mode of inheritance appears to be multifactorial, perhaps involving different degrees of expression under different environmental conditions. We show that the child's family history and environmental exposure can play a significant role in the development of asthma. The gradual increase in the number of affected siblings with increase in the number of affected parents suggest that asthma in Saudi children may be inherited and the mode of inheritance has yet to be determined.
735
B e n e r A. et al.
Eur. J. Epiderniol.
10. Jaggi O.P. (1974): Asthma and other allergies - New Delhi: Orient Longman.
Acknowledgements
We would like to thank King Abdulaziz City for Science and Technology for financial assistance. This research was supported by funds provided by the KACST (project AR-745). Also, we are very grateful to Miss Pamela Roberts of Dept. of Paediatrics and Mr. M. A1-Saddique of Dept. of Community Medicine Faculty of Medicine, UAE University for their excellent typing and assistance. REFERENCES
1. Adkinson J. (1920): The behaviour of bronchial asthma as an inherited character - Genetics 5: 363367. 2. Al-Frayh A.R., Al-Nahdi M., Bener A. and Al-Jawadi T.Q. (1989): Epidemiology of asthma and allergic rhinitis in two coastal areas of Saudi Arabia school children - International Journal of Allergie and Immunologie XXI, No. 10 December: 389-393. 3.
Carter C.O. (1969): Genetics of common disorders Brit. Med. Bull. 25: 52.
4. DrinkwaterH. (1909): Heredity of Bronchial Asthma Br. Med. J. 1: 88. 5. Edfors-Lubs M.L. (1971): Allergy in 7000 twin pairs Acta Allergologica 26: 249-285. 6. Hopp R.J., Bewtra A.K., Biven R., Nair N.M. and Townley G. (1986): Bronchial activity patterns in nonasthmatic parents of asthmatic - Ann. Allergy 61: 184-186. 7. Hopp R.J., Bewtra A.L. and Nair N.M. (1986): Methacholine inhalation challenge studies in selected pediatric population - Am. Rev. Respir. Dis. 134: 994.
11. Konig P. and Godfrey S. (1973): Prevalence of exercise-induced bronchial lability in families of children with asthma - Archives of disease childhood 48: 513-518. 12. Leigh D. and Marley E. (1967): Bronchial Asthma, A genetic, Population and Psychiatric study - Pergamon Press - Oxford. 13. Longo G., Strinat R. and Poli F. (1987): Genetic factors in non-specific bronchial hyperactivity - Am. J. Dis. Child. 141: 331-334. 14. Rodriguez V.A., Tejeiro F.A., Gomez E.A., Bacallao G.J. and Rodriguez G.R. (1975): Investigation of the prevalence and inheritance of bronchial asthma in San Antonia de la Banos, Cuba - Bull. Pan. Am. Health Org. 9: 221. 15. SAS Institute (1985): SAS users Guide: Statistics SAS Institute, Cary, NC. 16. Schenker M.B., Samet ZM. and Speizer F.E. (1983): Risk factors for childhood respiratory disease: the effects of host factors and home environment exposures - Am. Rev. Respir. Dis. 128: 1038-1043. 17. Schnyder V.W. (1960): Neurodermitis asthma-rhinitis - Acta Genet. Statist. Med. 10: Suppl.: 1-90. 18. Schwartz M. (1952): Heredity in bronchial asthma Acta Allergologica 5: Suppl.: 2-19. 19. Sibbald B., Horn M.E.C., Brain E.A. and Gregg L (1980): Genetic Factors in Childhood Asthma Thorax 35: 671-674. 20. Sibbald B., Horn M.E.C. and Gregg L (1980b): A family study of genetics of asthma and wheezy bronchitis -Arch. Dis. Child. 55: 354-357. 21. Spain W.C. and Cooke R.A. (1924): Studies in specific hypersensitiveness: The familial occurrence of hay fever and bronchial asthma - J. Immunol. 9: 521.
8. Hopp R.J., Bewtra A.K. and Watt G.D. (1984): Genetic analysis of allergic disease in twins - J. Allergy Clin. Immunol. 73: 265-270. 9. Horwood L.G., Ferguson D.M. and Shannon F.T. (1985): Social and familial factors in the development of early childhood asthma - Pediatrics 75: 859.
736
22. Townley G., Guirgis H. and Bewtra A. (1976): IgE levels and metacholine inhalation responses in monozygous and dizygous twins - J. Allergy Clin. Immunol. 57: 227-234.
Eur. J. Epidemiol. 0392-2990
Vol. 8, No. 5
JOURNAL
September 1992, p. 733-736
OF EPIDEMIOLOGY
H E R E D I T Y OF ASTHMA IN SAUDI POPULATION A. BENER .1, T.Q. AL-JAWADI**, M. SIMSEK*** and K.E. AL-NASSAR*** *Dept. o f Community Medicine - Faculty o f Medicine and Health Sciences United Arab Emirates University - P.O. B o x 1 7 6 6 6 - A l Ain - UNITED A R A B EMIRATES. **Dept. o f Paediatrics - College o f Medicine & K A A UH - King Abdulaziz University P.O. B o x 9025 - Jeddah 21413 - SA UDI A R A B I A . ***Department o f Biochemistry - Faculty o f Medicine - Kuwait University P.O. B o x 24923 - Safat-13110 - S T A T E OF K U W A I T .
Key words: Heredity - Asthma - Hay fever - Eczema - Parent - Child - Saudi population In a cross-sectional study, the prevalence of asthma, hay fever and eczema was studied in 1150 schoolchildren attending school in Jeddah Western region of Saudi Arabia. The family histories of asthma, hay fever and eczema were examined in first degree relatives. The age range of children studied was 7-12 years, with a mean of 9.3 years (470/0 boys and 530/0 girls;). A self-administered questionnaire was completed by the parents of the child to collect information concerning bronchial asthma, hay fever, and eczema in the target child and family history of respiratory allergy. A detailed family history and personal histories of asthma were available for 1035 Saudi children aged 7-12 years old. The rate of asthma and hay fever were significantly higher among siblings and offspring (cases) compared to their parents (p < 0.001). The results showed a high positive correlation between the relatives of affected children with respect to asthma and hay fever. These findings support the hypothesis that asthma and hay fever may be inherited in the Saudi population, but the mode of inheritance has yet to be determined.
INTRODUCTION
Heredity has long been considered to influence allergic disorders, particularly bronchial asthma. A genetic component in the etiology of certain allergic diseases has been generally accepted (5). Drinkwater (4) suggested that asthma is inherited as a single Mendelian dominant character. On the contrary, Adkinson (1) thought the disease to be a simple recessive trait. Later, Schnyder (17) concluded that the disease was inherited by a single autosomal dominant gene with reduced penetrance. But Leigh and Marley (12) considered that a multifactorial type of inheritance was more probable. The studies showed that hereditary asthma can best be explained by multiple gene inheritance (18). This type of inheritance, however, cannot be clearly 1 Corresponding author.
distinguished from single dominant gene inheritance in common disorders (3). The strong similarities between asthmatic and wheezy bronchitic children in their family histories of asthma and wheezy bronchitis suggest that these two forms of illness share a common genetic defect (19, 20). Most family studies provide a considerable genetic component, with positive family histories in 48-74 per cent of the cases (1, 21). The overall prevalence of asthma in first degree relatives of asthmatics was significantly higher than in the relatives of normal controls (20, 21, 6). Genetic mechanisms have been proposed to explain the presence of asthma in families (11). The prevalence of asthma was found to be even higher among twins examined (8, 22). Longo et al. (12) suggest that bronchial hyperactivity is an autosomal dominant trait with incomplete penetrance and is present in about 10% of the normal healthy population. Bronchial reactivity is inherent in all asthmatic (7).
733
Bener A. et al.
Eur. J. Epidemiol.
In Saudi Arabia, a few large, population-based studies have been conducted to define the important epidemiologic characteristics of allergic diseases amongst school age children. The aim of the present study was to investigate the hereditary of bronchial asthma, hay fever, and eczema among the Saudi population.
pair agreement. Agreement for the trait in question was valued one for each member of the pair, non-agreement was valued zero. In this study correlations were calculated for father-child, and for sib pairs of both like and unlike sex. RESULTS
MATERIALS AND METHODS
This cross-sectional, population-based study of bronchial asthma among schoolchildren aged 7-12 years was conducted in the city of Jeddah, western region of the Kingdom of Saudi Arabia. The field survey was conducted during the period January, 1986 February, 1989. Jeddah, with a population of 1.5 million, is located in the humid western coast of the country. One thousand one hundred and fifty school students aged 7-12 years were randomly selected in Jeddah city. A standardized questionnaire along with a letter of explanation was distributed among the selected students. The questionnaire was completed by the student's parents with the help of a nurse, senior medical student, allergist consultant and co-investigator. Information obtained from the respondents included: area of residence and social class of family; fathers occupation, mother's occupation; age, sex, history of asthma, hay fever and eczema in the target child; family history of respiratory allergy and parental smoking habits and parents daily cigarette consumption at home. Data were analyzed on the IBM computer of the College of Medicine at King Sand University. The SAS statistical package program was used to calculate the Chisquare values to assess the statistical significance of contingency table, SAS User Guide (15). The correlation was used to examine the relationships between asthmatic children and their parents. In the correlation method, the traits were classified into major categories of asthma, hay fever and eczema. Each parent-child pair in which either member showed the trait in question was examined for -
In Jeddah, a total of 1150 randomly selected students aged 7-12 years were provided with questionnaires to be completed by their parents. The parents of 1035 children (900/0) agreed to participate in the study. The age range of the children studied was 7-12 years, with a mean of 9.3 years; 470/0 were boys and 530/owere girls. The diagnosis of asthma and other allergic diseases from a questionnaire is often less exact than a physician's diagnosis. This data, however, includes many individuals that have been symptom-flee for many years since allergic symptoms become less frequent in older age groups. A physician's diagnosis would have to be based on the individual's own information about symptoms earlier in life rather than actual findings, and therefore would be similar to a questionnair diagnosis. One attempt has been made at estimating the reliability of the answers given by individuals. The validity of the questionnaire diagnosis was tested in 50 cases who were examined by an allergist at the King Abdulaziz University Hospital after they had returned the questionnaire. The consistency was high; only 90/0 had given inconsistent answers for bronchial asthma, only 13% had given inconsistent answers for hay fever and only 11.5% had given inconsistent answers for eczema. The distribution and comparison of asthma, hay fever and eczema among first degree relatives are shown in Table 1. The family history of asthma differed between asthmatic relatives. There were significantly more asthmatic siblings (15.3%) and offspring (16.2%) than asthmatic fathers (10.53%) and mothers (10.9%) (p < 0.001). The rate of asthma did not differ significantly between the siblings and offspring (p > 0.10). Similarly the prevalence rate of
TABLE 1. - The prevalence rate of asthma, hay fever and eczema among first degree relatives. RELATIVES Trait
Father
Mother
Siblings
Offspring (cases)
Significant differences*
Asthma
85 (10.5)
88 (10.9)
124 (15.3)
131 (16.2)
p < 0.001
Hay fever
51
(6.3)
35
(4.3)
105 (13.0)
202 (25.0)
p < 0.01
Eczema
36
(4.5)
48
(5.9)
37
(4.6)
62
(7.7)
p < 0.025
* = Chi-square test has been used for comparison of significant differences of father, mother, siblings and offspring.
734
Vol. 8, 1992
Asthma in Saudi Arabia
TABLE 2. - Correlation between relatives with respect to asthma, hay fever and eczema traits. RELATIVES Father-Child
Mother-Child
Sib-Sib
Traits
r(S.E.)
No. of pairs
r(S.E.)
No. of pairs
r(S.E.)
No. of pairs
Asthma
0.708 (0.104)
22
0.730 (0.09)
28
0.690 (0.062)
67
Hay fever
0.675 (0.109)
25
0.674 (0.120)
16
0.635 (0.070)
53
Eczema
0.709 (0.167)
8
0.721 (0.150)
11
0.689 (0.089)
35
hay fever did not differ between fathers (6.35%) and mothers (4.3%). But the prevalence rate of hay fever between siblings (130/0) and offspring (25%) were statistically significant (p < 0.001). Furthermore, the prevalence rate of eczema was higher in offspring (7.7%) than in siblings (4.6%), or fathers (4.5%) and mothers (5.9%). The increased rate of asthma, hay fever and eczema among siblings and offspring with fathers or mothers effected support the hypothesis that this trait is hereditary. Table 2 gives the correlation coefficient between first degree relatives. A comparison of the correlations in Table 2 among relatives, including father-child, mother-child and sib-sib showed a high positive correlation for the traits of asthma, hay fever and eczema (p < 0.001). The results of the present study could be interpreted as giving support to the hypothesis that bronchial asthma has an inherited component in Saudi children. DISCUSSION
The overall prevalence of asthma, hay fever and eczema were significantly higher between siblings and offspring than one parent (p < 0.001). The increased rate of asthma, hay fever and eczema among siblings and offspring with fathers and mothers affected, supports the hypothesis that asthma is inherited. It is generally agreed that the greater degree of inheritance leads to a greater likelihood of the offspring becoming sensitive. Furthermore, when both parents are affected the disease in the children appears earlier (10). Recently, Horwood et al. (9) showed very significant associations between the development of asthma and a large number of environmental, social and familial factors, including breast-feeding, parental smoking habits, pets in the child's family, stress in the family and family social background. A more recent
study (16) suggested that the environment in an inland town provides one or more additional risk factors for bronchial asthma in a study of two populations of Australian school children. It appears that the children in each town or city may have a different genetic expression for bronchial asthma due to different environmental exposures. In the present study, we showed that a higher prevalence of asthma in the humid coastal area and the child's family history play a significant role in the development of asthma. A1-Frayh et al. (2) reported that the prevalence rates of bronchial asthma, hay fever and eczema were higher in children than their fathers or mothers. A survey of bronchial asthma prevalence and inheritance patterns was carried out in the municipality of San Antonio, La Habana, Cuba by Rodriguez et al. (14). Their survey supported the hypothesis that the occurrence of bronchial asthma is strongly influenced by inheritance. Their results tend to confirm that the inheritance of bronchial asthma is autosomal and does conform to simple dominant or recessive inheritance patterns. Thus, a family history of allergy not only establishes predisposition but also determines the age at which the allergy will appear. Finally, strong similarities between asthmatic and wheezy bronchitic children in their family histories of asthma and wheezy bronchitis suggest that these two forms of illness share a common genetic defect (19, 20). Overall, our findings suggest that the particular mode of inheritance appears to be multifactorial, perhaps involving different degrees of expression under different environmental conditions. We show that the child's family history and environmental exposure can play a significant role in the development of asthma. The gradual increase in the number of affected siblings with increase in the number of affected parents suggest that asthma in Saudi children may be inherited and the mode of inheritance has yet to be determined.
735
B e n e r A. et al.
Eur. J. Epiderniol.
10. Jaggi O.P. (1974): Asthma and other allergies - New Delhi: Orient Longman.
Acknowledgements
We would like to thank King Abdulaziz City for Science and Technology for financial assistance. This research was supported by funds provided by the KACST (project AR-745). Also, we are very grateful to Miss Pamela Roberts of Dept. of Paediatrics and Mr. M. A1-Saddique of Dept. of Community Medicine Faculty of Medicine, UAE University for their excellent typing and assistance. REFERENCES
1. Adkinson J. (1920): The behaviour of bronchial asthma as an inherited character - Genetics 5: 363367. 2. Al-Frayh A.R., Al-Nahdi M., Bener A. and Al-Jawadi T.Q. (1989): Epidemiology of asthma and allergic rhinitis in two coastal areas of Saudi Arabia school children - International Journal of Allergie and Immunologie XXI, No. 10 December: 389-393. 3.
Carter C.O. (1969): Genetics of common disorders Brit. Med. Bull. 25: 52.
4. DrinkwaterH. (1909): Heredity of Bronchial Asthma Br. Med. J. 1: 88. 5. Edfors-Lubs M.L. (1971): Allergy in 7000 twin pairs Acta Allergologica 26: 249-285. 6. Hopp R.J., Bewtra A.K., Biven R., Nair N.M. and Townley G. (1986): Bronchial activity patterns in nonasthmatic parents of asthmatic - Ann. Allergy 61: 184-186. 7. Hopp R.J., Bewtra A.L. and Nair N.M. (1986): Methacholine inhalation challenge studies in selected pediatric population - Am. Rev. Respir. Dis. 134: 994.
11. Konig P. and Godfrey S. (1973): Prevalence of exercise-induced bronchial lability in families of children with asthma - Archives of disease childhood 48: 513-518. 12. Leigh D. and Marley E. (1967): Bronchial Asthma, A genetic, Population and Psychiatric study - Pergamon Press - Oxford. 13. Longo G., Strinat R. and Poli F. (1987): Genetic factors in non-specific bronchial hyperactivity - Am. J. Dis. Child. 141: 331-334. 14. Rodriguez V.A., Tejeiro F.A., Gomez E.A., Bacallao G.J. and Rodriguez G.R. (1975): Investigation of the prevalence and inheritance of bronchial asthma in San Antonia de la Banos, Cuba - Bull. Pan. Am. Health Org. 9: 221. 15. SAS Institute (1985): SAS users Guide: Statistics SAS Institute, Cary, NC. 16. Schenker M.B., Samet ZM. and Speizer F.E. (1983): Risk factors for childhood respiratory disease: the effects of host factors and home environment exposures - Am. Rev. Respir. Dis. 128: 1038-1043. 17. Schnyder V.W. (1960): Neurodermitis asthma-rhinitis - Acta Genet. Statist. Med. 10: Suppl.: 1-90. 18. Schwartz M. (1952): Heredity in bronchial asthma Acta Allergologica 5: Suppl.: 2-19. 19. Sibbald B., Horn M.E.C., Brain E.A. and Gregg L (1980): Genetic Factors in Childhood Asthma Thorax 35: 671-674. 20. Sibbald B., Horn M.E.C. and Gregg L (1980b): A family study of genetics of asthma and wheezy bronchitis -Arch. Dis. Child. 55: 354-357. 21. Spain W.C. and Cooke R.A. (1924): Studies in specific hypersensitiveness: The familial occurrence of hay fever and bronchial asthma - J. Immunol. 9: 521.
8. Hopp R.J., Bewtra A.K. and Watt G.D. (1984): Genetic analysis of allergic disease in twins - J. Allergy Clin. Immunol. 73: 265-270. 9. Horwood L.G., Ferguson D.M. and Shannon F.T. (1985): Social and familial factors in the development of early childhood asthma - Pediatrics 75: 859.
736
22. Townley G., Guirgis H. and Bewtra A. (1976): IgE levels and metacholine inhalation responses in monozygous and dizygous twins - J. Allergy Clin. Immunol. 57: 227-234.
