Children with asthma who are also obese are admitted to the hospital more often for asthma complications, according to a recent study in Japan.

Among children aged three to eight hospitalised for asthma, the obese patients were also more likely to be readmitted to hospital within 30 days and to stay at the hospital for a longer period of time, researchers found.

Stephen Montefort, lead consultant respiratory physician at Mater Dei Hospital, remarked that the link between obesity and asthma has long been known.

“It has been known for a long time that obesity is a risk factor for asthma and also makes asthma control more difficult,” said Prof. Montefort.

“Although we have ongoing studies, till now there are no concrete figures on Maltese asthmatics, but from experience I do note this association to be also present in Malta.”

The reasons are thought to be multifactorial but Prof. Montefort highlighted what are thought to be the main ones: a) possible anatomical features affecting mechanical alterations to structure of airway and lung tissue; b) obesity increasing lung and whole-body inflammatory processes including those that play a main role in the pathophysiology of asthma; c) problems in metabolism affecting lung function and the body’s response to asthma treatment, making asthma control more problematic.

“This leads to a vicious circle of asthmatics becoming more sedentary, making them more prone to gain further weight,” he pointed out.

The Japanese team investigated nearly 39,000 hospital discharge records for children between 2010 and 2015, classifying the patients as underweight, normal weight, overweight or obese according to World Health Organisation body mass index (BMI) categories.

Eight per cent of children were underweight, 75 per cent normal weight, nine per cent overweight and eight per cent obese.

The researchers then compared 30-day hospital readmission, need for intensive care, average total hospital costs and length of hospital stay among all patients.

Although we have ongoing studies, till now there are no concrete figures on Maltese asthmatics

They found that children in all four weight groups had similar needs for intensive care and total costs for hospitalisation. Obese children hospitalised with acute asthma problems were 26 per cent more likely to be readmitted to hospital within 30 days, however, and their average hospital stays were slightly longer than those of normal-weight children.

“We assumed that children with obesity were more likely to be hospitalised repeatedly,” lead author Yusuke Okubo of the National Research Institute for Child Health and Development in Tokyo. He said. “At this time, we are not sure the exact biological mechanisms for the associations between asthma and obesity.”

Potential risk factors for asthma include age, race and ethnicity, socioeconomic status, medication adherence, access to health care and a history of sinusitis, the study authors wrote online in Pediatric Allergy and Immunology.

Prof. Montefort commented: “As already stated, obesity does not affect asthma as a lone factor but seems to exert its effect on asthma together with other factors such as age, race and, of course, gender.

“Thus this could explain why female obese patients are more likely to have asthma and a more severe type of asthma.

“This is especially so after the onset of puberty when female asthmatics outnumber their male counterparts.”

A 2013 review of 35 studies in fact found that gender plays a role, with obese girls more likely to have asthma diagnoses than obese boys.

In a previous study using data on more than 74,000 children in the US who had asthma exacerbations in 2012, Okubo and her colleagues found that obese children had nearly double the odds of using mechanical ventilation, an average of $1,600 more in hospital charges and spent a quarter of a day longer in the hospital.

“Paediatric obesity is a public health problem and is associated with infections, chronic disorders, asthma and future heart disease,” Okubo said.

“Asthma is a chronic disorder and poor control of asthma may result in lower quality of life, school performance and self-confidence. Weight reduction and a healthy lifestyle is important for children to control asthma severity.”

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