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Respiratory Medicine (2014) xx, 1e4

Available online at www.sciencedirect.com

ScienceDirect journal homepage: www.elsevier.com/locate/rmed

SHORT COMMUNICATION

Indoor swimming pool attendance and respiratory and dermal health in schoolchildren e HITEA Catalonia Laia Font-Ribera a,b,c,d,*, Cristina M. Villanueva a,b,c,d, `s-Santos a,b,c,d, `cia-Lavedan a,b,c,d, Alı´cia Borra Esther Gra Manolis Kogevinas a,b,c,d,e, Jan-Paul Zock a,c,d,f a

Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain IMIM (Hospital del Mar Medical Research Institute), Barcelona, Spain c Universitat Pompeu Fabra (UPF), Barcelona, Spain d CIBER de Epidemiologı´a y Salud Pu´blica (CIBERESP), Spain e National School of Public Health, Athens, Greece f Netherlands Institute for Health Services Research, Utrecht, The Netherlands b

Received 24 February 2014; accepted 22 April 2014

KEYWORDS Asthma; Eczema; Upper respiratory tract infections; Pediatric; Epidemiology

Summary Background: Health benefits of swimming in pools may outweigh adverse health outcomes in children, but evidence from epidemiological studies is scarce or inconclusive for different health outcomes. We evaluated the association between indoor swimming pool attendance during childhood and respiratory and dermal conditions and symptoms in Catalan schoolchildren. Methods: Cross-sectional study in 2758 children aged 6e12 years from 18 primary schools in Barcelona province. Information on regular indoor swimming pool attendance in seven age periods, history of health conditions (asthma, wheezing, eczema, dermatitis, rhinitis, allergic rhinitis) and symptoms in the last 12 months (wheezing, dermatitis, rhinitis and number of cold, tonsillitis or otitis episodes) were collected through parental self-administered questionnaires. The associations between swimming pool attendance and health outcomes were evaluated using multivariate mixed logistic and Poisson regression models. Results: Regular indoor swimming before 2 years of age was not related to having ever had asthma (Odds Ratio (OR) Z 1.14; 95%CI Z 0.73e1.77), wheezing (OR Z 1.02; 95%CI Z 0.82 e1.28), or eczema (OR Z 1.09; 95%CI Z 0.87e1.36). Current indoor swimming was not associated with symptoms in the last 12 months (Incidence Rate Ratio for otitis was 0.94; 95% CI Z 0.77e1.15). Stratification by eczema or maternal education gave very similar results.

* Corresponding author. Centre for Research in Environmental Epidemiology (CREAL), Barcelona Biomedical Research Park, c/ Dr. Aiguader 88, 08003 Barcelona, Spain. Tel.: þ34 93 214 73 65. E-mail address: [email protected] (L. Font-Ribera). URL: http://www.creal.cat. http://dx.doi.org/10.1016/j.rmed.2014.04.018 0954-6111/ª 2014 Elsevier Ltd. All rights reserved.

Please cite this article in press as: Font-Ribera L, et al., Indoor swimming pool attendance and respiratory and dermal health in schoolchildren e HITEA Catalonia, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.04.018

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L. Font-Ribera et al. Conclusion: This new large population-based study indicates that regular indoor swimming during infancy does not increase respiratory, allergic or dermal symptoms in Catalan schoolchildren aged 6e12 years. ª 2014 Elsevier Ltd. All rights reserved.

Background It is believed that the health benefits of swimming in wellmaintained pools outweigh adverse health outcomes in schoolchildren, such as the risk of drowning, infections or respiratory symptoms [1]. However, a formal Health Impact Assessment cannot be carried out, since evidence from epidemiological studies is scarce or inconclusive for some health outcomes. The risk of respiratory or gastrointestinal infections associated with swimming pool attendance has been studied in babies [2e5] or preschoolers [6] but not in older children. The risk of childhood asthma associated with the exposure to the irritant environment in indoor chlorinated swimming pools has been discussed in recent years. Studies conducted in Belgium described an increased risk of asthma associated with early swimming [7,8]. However, studies in other European countries with larger population-based sample sizes [9,10], a longitudinal design [11] or a more detailed semi-quantitative exposure assessment [12] did not replicate the association found in Belgium. Conflicting results have also been described for the risk of allergic sensitization and eczema [10e14]. Exposure misclassification and reverse causation could be a concern in previous studies and more data are needed to draw final conclusions. We aim to evaluate the association between indoor swimming pool attendance during childhood and respiratory, allergic and dermal symptoms and conditions in Catalan schoolchildren.

Methods A cross-sectional study in 2008 within the HITEA project (www.hitea.eu), recruited children attending all grades of 18 schools in the Barcelona province (response rate 54%; N Z 2758). A questionnaire self-administered by the parents included questions from the validated ISAAC questionnaire [15] to ascertain: Having ever had asthma, wheezing, eczema (or atopic dermatitis), dermatitis (itchy rash coming and going for at least 6 months), rhinitis (sneezing, runny or blocked nose without cold), allergic rhinitis (or hay fever); Having had in the last 12 months wheezing, dermatitis, rhinitis; Number of times in the last 12 months having cold, tonsillitis, otitis. The question “Has your child attended an indoor swimming pool, at least once per week during one month or more?” was asked for seven age periods since birth up to the last 12 months. The following variables of pool attendance were created: Early (0e2 years of age); Late (3e6 years of age); Current (last 12 months). The main reason for attending or non attending pools was also asked. Logistic regression models and Poisson models were used to estimate Odds Ratios (OR) and

Incidence Rate Ratio (IRR), adjusting for potential confounders assessed by questionnaire: age, parental asthma (mother or father with ever asthma), maternal education (primary or less, secondary or university), passive smoking at home (currently and in the first year of life) and in utero, birth weight, gestational age, number of siblings and body mass index. Multivariate mixed models were fitted including school as a random-effect variable. Most variables had less than 5% of missing data, but a higher proportion was found for early swimming (38%), late swimming (26%), otitis (26%) and tonsillitis (24%), which varied between levels of maternal education. Missing data was considered as missing at random when adjusted by the observed data [16]. Chained equation methods were performed to impute missing values, using all variables available. One hundred complete data sets were generated and results were combined using Rubin’s rules [17].

Results Mean age was 9.0 years (range Z 4.5e12.8), 22% and 20% were, respectively, early and current regular indoor swimmers, 1.6% attended and 2.9% avoided swimming pools for health reasons. Early swimming was not related to respiratory, dermal or allergic symptoms (Table 1). Swimming between 3 and 6 years of age or swimming in outdoor pools led null associations with symptoms as well (results not shown). Current attendance was not associated with symptoms in the last 12 months (Table 1). In sensitivity analyses, the OR between early swimming and symptoms was not modified by eczema, as a proxy for atopy, maternal education, sex or second hand smoke. In complete-case analysis, the results remained very similar (results not presented), although an increased risk of tonsillitis episodes was found among current indoor swimmers (IRR Z 1.19; 95%CI Z 1.02e1.40).

Discussion Our study indicates that regular indoor swimming pool attendance does not increase the risk of asthma or wheezing in schoolchildren, which is consistent with other population-based studies [9e12]. We did not find an increased risk of eczema as was previously found in a very similar population [10], but it is in accordance with other population-based studies in UK [11] or The Netherlands [12]. Rhinitis and allergic rhinitis were also not affected in this study, as previously reported [10e12]. This is the first study exploring the risk of upper respiratory tract infections in schoolchildren related to swimming pool attendance. Previous studies in babies also did not find an increased risk of otitis associated with baby

Please cite this article in press as: Font-Ribera L, et al., Indoor swimming pool attendance and respiratory and dermal health in schoolchildren e HITEA Catalonia, Respiratory Medicine (2014), http://dx.doi.org/10.1016/j.rmed.2014.04.018

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Indoor swimming pool attendance and respiratory and dermal health in schoolchildren Table 1 Associations between health outcomes and regular indoor swimming (yes vs. no) A) in the early infancy (0e2 years of age) or B) currently (in the last 12 months). N Z 2758. Prevalence A) Early swimming Symptoms ever Asthmaa Wheezinga Dermatitisa Eczemab Rhinitsa Allergic rhinitsb B) Current swimming Symptoms last 12 months Wheezingc Rhinitisc Dermatitisc

Cold episodesd,* Tonsillitis episodese,* Otitis episodesf,*

OR (95%CI)

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parents were blinded to the hypothesis of this study and reverse causation appeared to be minimal”. In conclusion, this new large population based study indicates that regular indoor swimming pool attendance does not increase respiratory, allergic or dermal symptoms in school-aged children.

22%

Conflict of interest 6.1% 38.6% 16.2% 41.2% 27.7% 9.5% 20%

1.10 1.01 0.86 1.07 0.99 0.85

10.8% 24.1% 12.0% Median (P25eP75) 2 (1e2) 0 (0e1) 0 (0e1)

1.02 1.06 0.88 IRR

(0.70e1.73) (0.80e1.27) (0.63e1.16) (0.86e1.33) (0.77e1.27) (0.57e1.26)

(0.73e1.42) (0.85e1.34) (0.64e1.21) (95%CI)

1.00 (0.93e1.08) 1.10 (0.94e1.28) 0.94 (0.78e1.13)

Regular swimming: at least once per week during one month or more. Multilevel models with School as a random effect, adjusted by: a) parental asthma, age; b) parental asthma, age, maternal education; c) parental asthma, passive smoking at home; d) age, maternal education; e) number of siblings; f) age, body mass index. OR: Odds Ratio. 95%CI: 95% Confidence Interval. IRR: incidence rate ratio. *Poisson model (number of episodes during the last 12 months).

swimming [2e5]. In the complete-case analysis, recent tonsillitis episodes were more common among children currently attending indoor pools. The tonsillitis variable had a 24% of missing data and this association was not found in the imputed dataset. To our knowledge no other studies have evaluated the risk of cold or tonsillitis associated with swimming pools. This study also shows that the vast majority of schoolaged children does not attend or avoid swimming for health reasons, as described in The Netherlands [12] and Spain [10]. This indicates that reverse causation is unlikely to be a main source of bias in epidemiological studies on swimming pool attendance and health effects during childhood. The large proportion of missing values in the early swimming question is a concern. The question may have been complex and misleading for a self-administered questionnaire, especially among less educated families. As increasingly recommended [16], we applied multiple imputation to avoid selection bias, although complete-case analysis gave very similar results. On the other hand, the swimming questions used are more specific, in terms of swimming pool type, frequency and duration, than those in some previous studies [10,11]. The cross-sectional design with retrospective self-reported information is another limitation, common in the studies on this topic [2,4,6e8,10,12e14]. However, recall bias is not likely since

Authors declare no conflict of interest.

Acknowledgements We thank L. Arjona (CREAL) for her contribution in the fieldwork. This study was financially supported by the European Commission as part of HITEA (Health Effects of Indoor Pollutants: Integrating Microbial, Toxicological and Epidemiological Approaches), Grant agreement no. 211488 under the Seventh Framework Programme, Topic ENV.2007.1.2.1.1.

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L. Font-Ribera et al. swimming in chlorinated pools. Int J Hyg Environ Health 2014; 217:38e45. [15] Mata Ferna ´ndez C, Ferna ´ndez-Benitez M, Pe ´rez Miranda M, et al. Validation of the Spanish version of the Phase III ISAAC questionnaire on asthma. J Investig Allergol Clin Immunol 2005;15:201e10. [16] Sterne JA, White IR, Carlin JB, Spratt M, Royston P, Kenward MG, Wood AM, Carpenter JR. Multiple imputation for missing data in epidemiological and clinical research: potential and pitfalls. BMJ 2009;338:b2393. [17] Royston P. Multiple imputation of missing values. Stata J 2004; 4:227e41.

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Indoor swimming pool attendance and respiratory and dermal health in schoolchildren--HITEA Catalonia.

Health benefits of swimming in pools may outweigh adverse health outcomes in children, but evidence from epidemiological studies is scarce or inconclu...
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