Are children׳s asthmatic symptoms related to ambient temperature? A panel study in Australia.

OBJECTIVES: To examine the short-term effects of ambient temperature on respiratory symptoms for school children with asthma across Australia. METHODS: A panel of 270 children (7-12 years) with asthma was recruited from six Australian cities. They were asked to record their respiratory symptoms every day in the morning (for night-time symptoms) and evening (for daytime symptoms) for four weeks. Daily ambient temperature, relative humidity and air pollution data were obtained from fixed monitors nearby. A mixed logistic regression model was used to examine the effects of ambient temperature on respiratory symptoms adjusted for children's sex, age, standing height, weight and air pollution. Subjects were specified as random effects. RESULTS: The relationships between ambient temperature and respiratory symptoms were linear. Increasing temperatures induced the risks of children's asthmatic symptoms, especially for "wheeze/chest tightness" and to a lesser extent for "cough/phlegm". The effects were acute and lasted for four days (lag 0-3) in general. With increasing ambient temperature, boys were more at risk than girls. CONCLUSIONS: High ambient temperature is a risk factor for respiratory symptoms in children with asthma. As ambient temperature increases, policies and strategies for rising temperatures will be necessary to protect asthmatic children.

An Australian national panel study of diurnal temperature range and children's respiratory health.

BACKGROUND: It is still uncertain whether diurnal temperature range (DTR) affects children's respiratory function. OBJECTIVE: To examine the effects of DTR on lung function and respiratory symptoms for school children with asthma in Australia. METHODS: A panel of 270 children (ages 7-12 years) with asthma living in 6 Australian cities was recruited. They were asked to perform 3 successive forced expiratory maneuvers using a portable electronic peak flow meter twice daily for 4 weeks. The highest values for peak expiratory flow (PEF) were stored for each session. At the same time, they were asked to record their respiratory symptoms (eg, cough and/or phlegm and wheeze and/or chest tightness) every day in the morning (for nighttime symptoms) and evening (for daytime symptoms). Daily data on different metrics of ambient temperature and air pollution were obtained from fixed monitors nearby. Relative humidity data were downloaded from the Weather Underground website. Mixed models, adjusting for children's individual characteristics and air pollution, were used to examine the effects of DTR on PEF and respiratory symptoms. RESULTS: DTR had linear effects on PEF and respiratory symptoms. An increase in DTR induced a reduction in PEF and increased the occurrence of respiratory symptoms. In general, the effects lasted for 3 days (lag, 0-2 days). The effects occurred for both boys and girls. CONCLUSION: Our findings provide evidence that DTR had significant effects on lung function and respiratory symptoms for children with asthma. These results indicate that it is important and necessary to protect children with asthma from the effect of unstable weather.

Ambient temperature and lung function in children with asthma in Australia.

The association between ambient temperature and lung function in children with asthma is still uncertain. A panel of 270 children (aged 7-12 years) with asthma was recruited from six Australian cities. They performed three successive forced expiratory manoeuvres twice daily for 4 weeks. The highest peak expiratory flow rate (PEF) and forced expiratory volume in 1 s (FEV1) were stored for each session. During the same period, data were obtained daily on ambient temperature, relative humidity and air pollution. Mixed models were used to examine the effects of temperature on lung function, controlling for individual characteristics and environmental factors. Ambient temperature was negatively related to both morning and evening PEF and FEV1 for 0-3 days lag. In general, the effects of temperature were stronger in males than in females for evening PEF, while the effects were stronger in females for evening FEV1. Children with asthma living in southern cities were more sensitive to high temperature than those in the northernmost city. Higher ambient temperature is associated with lower lung function in children with asthma. Preventive health policies will be required to protect children with asthma from increasingly frequent high temperatures.