Spring may not be the most dangerous time for children with asthma triggered by pollen, according to an Australian study that shows most pollen-related asthma health issues in children occur in the cooler months.

In contrast for adults there were peaks of pollen-related asthma problems in the warmer months such as February and October, according to researchers at the University of Adelaide.

The findings indicate a need for year-round pollen monitoring and related health campaigns to provide effective public health prevention for asthma, the researchers said in BMJ Open (link here).

The study analysed 15 years of grass, weed and tree pollen counts alongside hospital and ambulance data and found that for children, the riskiest period for grass pollen-related attacks was autumn (May).

For children under the age of 18 there were 22,114 hospital admissions, 39,813 ED presentations and 3774 ambulance callouts for asthma, respectively.

Positive associations with weed pollen in children was seen from February to May across all health outcomes.

Children’s asthma morbidity was associated with tree pollen in August and September, with incidence rate rations (IRR) ranging from 1.14 for ED presentations for tree pollen in August to 1.98 for weed pollen in February.

The researchers from the university’s School of Public health said August was an important time for tree pollen to be relevant in SA, as trees start to flower, and pollen is wind distributed from sources including cypresses, birch, Myrtaceae-related bushes and trees, pines, olive trees and casuarina.

For adults, for adults, grass pollen was a trigger for asthma morbidity in October. And as for children, asthma risks increases were observed in relation to weed pollen for adults in February, when there was a positive relationship with ambulance callouts and ED presentations for asthma.

There were no links between tree pollen and asthma morbidity in adults.

The researchers said the findings of multiple peak periods of asthma related to pollens showed the usefulness of year-round pollen data. The temperate climates of south east Australia resulted in pollen counts having several peaks, they noted, as shown in a recent study in Sydney that reported pollen peaks from January to April and a second peak in July to October.

The authors said the pollen-related asthma peaks in late summer-autumn and in late winter-spring, “[indicate] the need of asthma vigilance across the year rather than a focus of prevention activity during spring as is currently the case.”

“Future preventive measures should mirror the identified risk periods with monitoring extended to all pollen taxa, preferably all year round, and appropriately timed programmes to alert the public to pollen-related risk and encourage preventive action,” they concluded.