NZ lockdown puts heart failure theory to the test

Each winter, there is a surge in heart failures. Some scientists suggest this is linked to more respiratory viruses like RSV and the flu circulating in the colder months. However new research showed New Zealand’s lockdown led to a significant drop in the spread of these infectious respiratory diseases, but little change in hospital admissions for cardiac problems. The authors say this suggests the respiratory diseases are not linked to the winter heart-failure peak, and something else is behind it – possibly the colder temperatures or more pollution over winter.

Journal/conference: Respirology

Link to research (DOI): 10.1111/resp.14119

Organisation/s: University of Waikato, University of Otago, Waikato Hospital

<!–Last updated: Mon 9 Aug 2021–> Funder: Sarah Fairweather was funded by a summer scholarship from the Waikato Medical Research Foundation. Chris Lewis at the New Zealand Ministry of Health kindly provided the hospital admissions data.

Media release

From: Dr Cat Chang, Author, Waikato Hospital

COVID-19 pandemic restrictions in New Zealand from March 2020 led to marked reductions in all circulating respiratory viruses – including those that were already present in NZ at the time of the first lockdown.  This is the biggest respiratory virus free “bubble” ever documented and viral levels stayed low despite lifting of restrictions through to when the country was back at level 1.

We observed that in 2020, winter respiratory hospital admissions were at the same level as that normally seen in the summer.  Our results confirm that respiratory viruses play a central role in driving seasonal respiratory admissions and highlights the importance of social distancing in the transmission of respiratory viruses.

There is a well-recognised winter peak in cardiovascular disease but the mechanism by which this happens in not clear.  Respiratory viruses including influenza and severe respiratory infections have been associated with these observed peaks in some studies but whether it is causal or merely exist at the same time is not known.  Despite unprecedented low/absent levels of circulating respiratory viruses in the winter of 2020, we did not observe a significant change in the number of admissions for heart attacks and heart failure.   This suggests that the proposed viruses causing more winter cardiovascular disease is not the main contributing factor in our population.

Our study analysed national admission trends for the first 33 weeks of the year (up to when Auckland went into a second lockdown) as the whole country can be viewed as one bubble.  We have plans to analyse the remaining weeks of 2020 through to winter 2021 and study further trends in respiratory viruses in New Zealand.

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