Prenatal and post-natal exposure to antibiotics and risk of asthma in childhood.

BACKGROUND: Evidence on the association between post-natal exposure to antibiotics and the development of asthma is extensive, but inconsistent and even less is known about prenatal exposure. OBJECTIVE: The aim of this study was to examine the associations between prenatal and post-natal exposure to different antibiotics and the risk of childhood asthma in a population- and register-based nested case-control study. METHODS: All children who were born in 1996-2004 in Finland and diagnosed with asthma by 2006 were identified from a national health register. For each case, one matched control was selected. Information on asthma diagnoses, purchased anti-asthmatic drugs and antibiotics as well as putative confounders was obtained from national health registries. The associations were analysed using conditional logistic regression for children diagnosed at the age of 3 years or later (n = 6 690 case-control pairs). RESULTS: Maternal use of any antibiotics during pregnancy was associated with an increased risk of asthma in the offspring [adjusted odds ratio (OR) = 1.31 (95% confidence interval (CI): 1.21-1.42)]. Several maternal specific antibiotics were associated with the risk of asthma, and the strongest association was observed for cephalosporins [OR = 1.46 (95% CI 1.30-1.64)]. Child's use of antibiotics during the first year of life was associated with an increased risk of asthma [OR = 1.60 (95% CI 1.48-1.73)]. Child's use of cephalosporins [OR = 1.79 (95% CI 1.59-2.01)], sulphonamides and trimethoprim [OR = 1.65 (95% CI 1.34-2.02)], macrolides [OR = 1.61 (95% CI 1.46-1.78)] and amoxicillin [OR = 1.46 (95% CI 1.35-1.58)] was associated with an increased risk of asthma. CONCLUSIONS AND CLINICAL RELEVANCE: Both prenatal and post-natal exposure to antibiotics was associated with an increased risk of asthma. The potential role of adverse effects of antibiotics on the gut microbiota and the development of asthma should be further explored.

An examination of word frequency and neighborhood density in the development of spoken-word recognition.

In this study, the effects of word-frequency and phonological similarity relations in the development of spoken-word recognition were examined. Seven-, 9-, and 11-year-olds and adults listened to increasingly longer segments of high- and low-frequency monosyllabic words with many or few word neighbors that sounded similar (neighborhood density). Older children and adults required less of the acoustic-phonetic information to recognize words with few neighbors and low-frequency words than did younger children. Adults recognized high-frequency words with few neighbors on the basis of less input than did all three of the children's groups. All subjects showed a higher proportion of different-word guesses for words with many versus few neighbors. A frequency x neighborhood density interaction revealed that recognition is facilitated for high-frequency words with few versus many neighbors; the opposite was found for low-frequency words. Results are placed within a developmental framework on the emergence of the phoneme as a unit in perceptual processing.

Young children's age-of-acquisition estimates for spoken words.

This study was concerned with the impact of stimulus familiarity on young children's ability to recognize spoken words and make explicit judgments about them. In Experiment 1, 5-year-olds made age-of-acquisition (AOA) estimates for a set of words that were very similar to estimates made by older children and adults. In Experiment 2, young children's picture recognition, mispronunciation detection, and vocabulary monitoring performance all varied systematically with these AOA estimates and with a stimulus-type (intact-mispronounced) manipulation. Subjective AOA estimates (whether from children or from adults) proved to be a better predictor of performance than did two objective familiarity measures and subjective imageability. These results point to considerable metalexical knowledge on the part of young children or explicit sensitivity regarding their own vocabulary knowledge. In addition, the results lend some support to the notion that actual AOA contributes to subjective AOA estimates.

The growth of lexical constraints on spoken word recognition.

In this study, we examined the influence of various sources of constraint on spoken word recognition in a mispronunciation-detection task. Five- and 8-year-olds and adults were presented with words (intact or with word-initial or noninitial errors) from three different age-of-acquisition categories. "Intact" and "mispronounced" responses were collected for isolated words with or without a picture referent (Experiment 1) and for words in constraining or unconstraining sentences (Experiment 2). Some evidence for differential attention to word-initial as opposed to noninitial acoustic-phonetic information (and thus the influence of sequential lexical constraints on recognition) was apparent in young children's and adults' response criteria and in older children's and adults' reaction times. A more marked finding, however, was the variation in subjects' performance, according to several measures, with age and lexical familiarity (defined according to adults' subjective age-of-acquisition estimates). Children's strategies for responding to familiar and unfamiliar words in different contexts are discussed.