New Zealand Study Shows Adding Insulation to Homes Reduced Asthma


The findings come from a retrospective cohort study conducted in New Zealand, which examined the impact of a government subsidized insulation program on respiratory health.

Retrofitting home insulation can reduce the onset of chronic respiratory diseases such as asthma by up to 10%, according to a new study, which said the effect was even greater in children under the age of 15.

The findings come from a retrospective cohort study conducted in New Zealand, which examined the impact of a government-subsidized insulation program on respiratory health.

Before building codes changed in 1977, there was no requirement to insulate New Zealand homes, and many are cold by global standards, according to the authors. Cold air is a trigger for asthma, as is mold.

The researchers used linked data from the national intervention program, connecting residents whose homes were insulated to their health records. They also included prescription drug records linked to the residents using an encrypted unique identifier to examine the dispensing of 3 groups of respiratory drugs:

  • Antibiotics used for infectious respiratory disease
  • Mast-cell stabilizers, inhaled corticosteroids, and long-acting beta-adrenoceptor agonists (LABA) prescribed to prevent chronic respiratory symptoms
  • Anticholinergics and short-acting beta-adrenoceptor agonists (SABA) prescribed to treat acute flare-ups of asthma and wheezing, as well as prednisone as a marker of severe asthma or chronic obstructive pulmonary disease

The study cohort was made up of more than 1 million people who had lived in 1 or more of 205,001 retrofitted homes, for all or part of the 6-year study period. Additionally, there were 157,338 people and 49,457 houses in a 6-year continual occupancy nested cohort.

A difference-in-difference approach was used to compare the before and after change in medicines dispensed to the intervention group compared with pharmaceuticals dispensed to controls. The intervention group were residents who had their homes insulated between July 2009 and December 2011, and were followed for 3 years before and 3 years after insulation was installed.

While there was no change in prescriptions used to prevent respiratory exacerbations, researchers did find a difference in prescriptions dispensed to treat the new onset of respiratory problems, where they were lower in homes retrofitted with insulation (odds ratio, 0.90; 95% CI, 0.86–0.94).

In addition, there was also a 4% reduction in prescription for treating exacerbations (relative rate ratio, 0.96; 95% CI, 0.96–0.97).

Subgroups that saw an even greater respiratory benefit from having insulation installed included children under the age of 15 (OR, 0.85; 95% CI, 0.75–0.98); people of European ethnicity (OR, 0.87; 95% CI, 0.82–0.92; people who are the least deprived (OR, 0.80; 95% CI, 0.70–0.90); and those who were the most deprived (OR, 0.88; 95% CI 0.8,0–0.97).

Prior work has shown that children are less likely to develop asthma symptoms when their home environment is warmer and less prone to damp and mold. In a statement, one of the authors said the current findings illustrate the impact of duration of unhealthy home environments on asthma development in children.

Another study related to this effort showed that the insulation program reduced monthly drug costs.

“Retrofitting insulation is a relatively inexpensive way of not only making houses warmer and more affordable to heat but also healthier to live in,” said Caroline Fyfe, PhD, of the University of Otago, in a statement.


Fyfe C, Telfar Barnard L, Douwees J, Howden-Chapman P, Crane J. Retrofitting home insulation reduces incidence and severity of chronic respiratory disease. Indoor Air. Published online August 21, 2022. doi:10.1111/ina.13101

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