While we're all tensely watching the All Blacks at this year's Rugby World Cup, a team of researchers will perhaps be more interested in us.

Or more specifically, what's going on with our tickers as the drama unfolds.

The same team of New Zealand researchers who have studied how fans have reacted to the last few tournaments will again be looking to analyse hospital data recorded during this year's cup campaign.

In their most recent paper, the team - comprised of sports scientists Dr Peter Olsen and Dr Paul Bradley, cardiologist Dr John Elliott and biostatistician Professor Chris Frampton - used hospital data recorded in the past four world cup tournaments to study the risk of heart failure for spectators during knock-out rounds.


They found that women are most at risk of heart failure during these tense matches - especially if they're made to feel stressed or angry - while men were susceptible to arrhythmias, or an irregular heartbeat.

Dr Elliott, an Associate Professor at Otago University's Department of Medicine and an interventional cardiologist at Christchurch Hospital, told the Herald he and Dr Olsen planned to follow up on the data collected during this tournament for another paper.

"That information should be available from the New Zealand Health Information Service in about six months, and it's something Peter and I intend to look at in about a year from now," said Dr Elliott, who recorded his own heart rate while attending the nerve-wracking 2011 cup final at Eden Park.

In an interview with international science site ResearchGate, Dr Elliott and his fellow researchers explained how passionate fans with pre-existing or undiagnosed heart conditions were most at risk, particularly if their team lost.

These problems were more likely to happen during the knockout stages or close matches - when New Zealand lost to Australia in the 2003 semi-final, cardiac hospital admissions more than doubled in male and females.

In contrast, when New Zealand won a similar semi-final in 2011 against Australia, there was no significant increase in cardiac hospital admissions.

Specifically, they said, women appeared to be more likely to suffer from heart failure due to diastolic impairment or abnormal filling secondary to hypertensive heart disease and ventricular hypertrophy.

"For example, the stress of watching a sporting event may increase blood pressure and impair filling of the heart, leading to increased heart failure in women."


They chose to focus on New Zealand fans given their enthusiasm and high expectations of the men in black winning every game.

"Consequently, with such a passionate fan base, New Zealand hosting the 2011 Rugby World Cup, a TV audience share of 98 per cent for the final match, and successive failures to win the tournament since 1987, we thought it would be interesting to determine the relationship between RWC matches and cardiac hospital admissions," they said.

"If a relationship was found this could also be used to inform those at risk, and ensure adequate hospital and emergency staffing during large sporting events."

Watching rugby, like any sports, was capable of generating a wide range of emotions, and acute emotional triggers, such as anger, had been shown to increase the likelihood or risk of a cardiac event.

However, they said, the risk to the general population was probably elevated but still very low overall.

"It is probably the same level of risk as driving a car on a long weekend: the likelihood of having an accident is higher, but still quite small overall for the general population."

German researchers who undertook a similar a study when that country hosted the 2006 FIFA World Cup found even higher cardiac events during world cup games than the New Zealand team's own research - in Germany, fans were at three to four times greater risk.

"Some research indicates large sporting events have no effect on the cardiac hospital admissions," the researchers said.

"Nevertheless, we believe a limitation of these studies is generally they did not compare hospital admission over a long enough time frame, or similar teams when the team of interest won or lost in knockout stages of a tournament.

"For example, we compared data in October/November from 1999-2011 and also compared this to another, less emotional large audience for a TV event: The Opening ceremony of the Sydney Olympics in 2000."

The follow-up study they undertake after the coming world cup would determine if the trends previously observed persisted.

"This year's Cup is hosted by England and Wales so, given the nature of the rivalry between these two rugby nations and the knockout nature of the games, it would be interesting to determine the outcome of their games in a very tightly contested pool in the 2015 RWC."