The impact of parity and age at first and last childbirth on the prevalence of delayed-onset asthma in women: The Korean National Health and Nutrition Examination Survey.

OBJECT: Asthma is a chronic inflammatory airway disease. The aim of this study was to investigate the relationships between asthma and reproductive factors, including age at first childbirth and parity, in a representative sample of Korean women.

MAIN OUTCOME MEASURES: We analyzed data from the Korean National Health and Nutrition Examination Survey (2010-2012). A total of 7837 adults who completed a questionnaire and examination were evaluated. The presence of asthma was based on the Health Interview Survey. Reproductive factors were estimated by trained interviewers using participant recall.

RESULTS: The women with asthma were significantly older than those without asthma. BMI, hypertension, education level, income level, occupation, alcohol consumption, and age at menarche and first birth were significantly associated with the diagnosis of asthma. Higher parity was positively associated with later-onset asthma. In addition, women who were younger at first birth had a greater prevalence of later-onset asthma. After controlling for confounders, being aged under 20 at first birth was significantly associated with an asthma diagnosis compared with women aged 25-29 at first birth (OR [95% CI]: 1.81 [1.14-2.89]).

CONCLUSIONS: Although higher parity was associated with asthma in women, its significance disappeared after adjustment. These results warrant future studies to explore the mechanisms responsible for the association between reproductive factors and asthma.