Breastfeeding and childhood asthma: a six-year population-based cohort study.

BACKGROUND: The question of the protective effect of breastfeeding on development of asthma has raised substantial interest, but the scientific evidence of the optimal duration of breastfeeding is controversial. METHODS: The authors elaborated the optimal duration of breastfeeding with respect to the risk of asthma primarily, and secondarily to the risk of persistent wheezing, cough and phlegm in school age in a population-based cohort study with the baseline in 1991 and follow-up in 1997. The study population comprised 1984 children aged 7 to 14 years at the end of the follow-up (follow-up rate 77). Information on breastfeeding was based on the baseline survey and information on the health outcomes at the follow-up. RESULTS: There was a U-shaped relation between breastfeeding and the outcomes with the lowest risk with breastfeeding from four to nine months for asthma and seven to nine months for persistent wheezing, cough and phlegm. CONCLUSION: Our results suggest a U shape relation between duration of breastfeeding and risk of asthma with an optimal duration of 4 to 6 months. A true concave relation would explain the inconsistent results from the previous studies.

Home dampness and molds, parental atopy, and asthma in childhood: a six-year population-based cohort study.

Previous studies of how parental atopy and exposure to dampness and molds contribute to the risk of asthma have been mainly cross-sectional or prevalent case-control studies, where selection and information bias and temporality constitute problems. We assessed longitudinally the independent and joint effects of parental atopy and exposure to molds in dwellings on the development of asthma in childhood. We conducted a population-based, 6-year prospective cohort study of 1,984 children 1-7 years of age at the baseline in 1991 (follow-up rate, 77%). The study population included 1,916 children without asthma at baseline and complete outcome information. The data collection included a baseline and follow-up survey. The outcome of interest was development of asthma during the study period. The studied determinants were parental allergic diseases and four indicators of exposure at baseline: histories of water damage, presence of moisture and visible molds, and perceived mold odor in the home. A total of 138 (7.2%) children developed asthma during the study period, resulting in an incidence rate of 125 cases per 10,000 person-years [95% confidence interval (CI), 104-146]. In Poisson regression adjusting for confounding, parental atopy [adjusted incidence rate ratio (IRR) 1.52; 95% CI, 1.08-2.13] and the presence of mold odor in the home reported at baseline (adjusted IRR 2.44; 95% CI, 1.07-5.60) were independent determinants of asthma incidence, but no apparent interaction was observed. The results of this cohort study with assessment of exposure before the onset of asthma strengthen the evidence on the independent effects of parental atopy and exposure to molds on the development of asthma.

Environmental tobacco smoke and adult-onset asthma: a population-based incident case-control study.

OBJECTIVES: The authors assessed the effects of environmental tobacco smoke (ETS) on the development of asthma in adults. METHODS: In the Pirkanmaa district of South Finland, all 21- to 63-year-old adults with new cases of asthma diagnosed during a 2.5-year period (n = 521 case patients, out of 441 000 inhabitants) and a random sample of control subjects from the source population (932 control subjects) participated in a population-based incident case-control study. RESULTS: Risk of asthma was related to workplace ETS exposure (adjusted odds ratio [OR] = 2.16; 95% confidence interval [CI] = 1.26, 3.72) and home exposure (OR = 4.77; 95% CI = 1.29, 17.7) in the past year. Cumulative ETS exposure over a lifetime at work and at home increased the risk. CONCLUSIONS: This study indicates for the first time that both cumulative lifetime and recent ETS exposures increase the risk of adult-onset asthma.

Pets, parental atopy, and asthma in adults.

BACKGROUND: Studies of exposure to pets and the risk of asthma have provided conflicting results. OBJECTIVE: We conducted a population-based incident case-control study to assess the relationship of current and previous pet keeping with the risk of adult-onset asthma. We also investigated whether genetic propensity as a result of parental atopy modifies these relations. METHODS: From the source population of 441,000 inhabitants of a geographically defined area in South Finland, we systematically recruited, during a 2.5-year period, all new cases of asthma in 21- to 63-year-old adults and randomly selected control subjects. The clinically diagnosed case series consisted of 521 adults with newly diagnosed asthma and a control series of 932 control subjects. Information on current and past exposure to hairy pets was collected by using a self-administered questionnaire. RESULTS: In logistic regression analysis the risk of asthma was lower among subjects with pets during the past 12 months (adjusted odds ratio [OR], 0.74; 95% confidence interval [CI], 0.57-0.96) but higher among subjects with pets more than 12 months previously (adjusted OR, 1.39; 95% CI, 1.05-1.84). Parental atopy increased the risk of asthma (OR, 1.88; 95% CI, 1.47-2.41), but there was no interaction between parental atopy and pet exposure. CONCLUSIONS: The present results are consistent with the hypothesis that both keeping furry pets and parental atopy increase the risk of asthma development in adulthood. Parental atopy does not modify the effects of pet exposure. The negative association between current pets and the risk of asthma is consistent with selective avoidance of these pets by symptomatic individuals.