INTRODUCTION
Asthma is the most common non-communicable diseases among children, characterized by shortness of breath, rapid breathing, chest tightness and wheezing.1,2 The prevalence of childhood asthma has increased worldwide. Asthma is one of top reasons why children miss school days and visit emergency department, and it can affect children’s long-term health by impairing lung function and increasing risk of developing Chronic Obstructive Pulmonary Disease (COPD).3 The etiology of asthma is not fully understood. Thus, identifying risk factors for childhood asthma could be beneficial to increase early detection of the disease and prevent adverse outcomes later in life.
Asthma can be genetically heritable and the heritability estimated by twin studies ranges from 35% to 70%.4 Although, genome-wide research has identified a number of asthma susceptibility loci, they only account for a small fraction of the heritability.5,6 There are still genetic risk factors waiting to be unveiled. A family history could provide useful information for gene susceptibility, if shared environmental factors were controlled.7 Parents with asthma has been widely reported to contribute to increasing offspring’s asthma risk.8,9 However, the relative roles of maternal asthma and paternal asthma on their offspring’s asthma risk is controversial. Some studies found that a maternal had stronger impact than a paternal, whereas others had the opposite findings.10 In addition, grandparents are relatives who share 25% of a person’s genes.11 Rare studies have reported the impact of a grandparental on a child’s risk of developing asthma.
In this study, we aimed to investigate the multi-generational hereditary patterns of asthma. We estimated the familial risks of asthma for children who had family members (parents, maternal grandparents and paternal grandparents) affected by asthma after controlling for potential environmental risk factors (e.g. environment tobacco exposure, ambient air pollution and pet keeping).12-14 In addition, we also estimated the impact of parents on the association between grandparental asthma and childhood asthma.