Heading in football has been under the spotlight for more than 20 years - scrutiny born of fear and confusion.

Fear that the act itself could have long-term effects on the brains of those who do it most.

Confusion over why it happens and how great the risks really are.

Science has begun to provide some answers, but there is still a long way to go before we fully understand the impact of something that has been part of the game since its very beginning.

The research to date has been worrying enough to force some rule changes by governing bodies.

But, for many people, the threat still feels abstract - worthy of attention only when another of the game's greats is diagnosed with dementia or Alzheimer's.

Some take comfort from the belief that football has changed, that coaching is different, the balls are lighter and the modern game is played more on the ground.

But is it?

Well, that very much depends on which league you are watching.

New data shows the Scottish Premiership records significantly more headers per match than most of Europe's top leagues.

BBC Scotland looked at figures from the start of season 2021 until now, covering aerial duels and headed clearances, in the top leagues of Scotland, England, Italy, France, Germany and Spain.

In the Premiership, players challenge for the ball in the air, on average, 42.5 times per match - a 71% increase on France's Ligue 1, at 28.5 times per match.

Fans watching the Premier League in England can expect to see 28.7 aerial duels per match - nearly 50% fewer than Scotland.

It is a similar picture in Germany, Spain and Italy, who all challenge for the ball in the air significantly less than in Scotland.

With headed clearances, France provides the starkest comparison.

In Ligue 1, you will find an average of 16.8 headed clearances per match - that is almost 50% fewer than Scotland's 24.7 per match.

The EPL (21.3), Bundesliga (21.2), Serie A (18.2) and La Liga (19.4) all clear the ball with the head less than in Scotland.

Further data also shows the trend continuing with comparable leagues.

There are almost 60% fewer aerial duels in the Czech First League.

The top leagues in Denmark, Sweden and Norway also record over 40% fewer aerial duels than the Premiership.

There are also fewer headed clearances in Denmark, Norway, Sweden, Czech Republic and Austria.

Looking at the combined metrics of Scotland compared to 10 top leagues around the continent, there are more than 35% more heading actions in Scotland.

The figures may not come as a shock to those who watch Scottish football on a regular basis, but they do throw up questions about what it means for the discussion around safety.

Since the death of former England centre-forward Jeff Astle from dementia in 2002, scientists have increasingly linked repeated head impacts to chronic traumatic encephalopathy (CTE), which can also lead to neurodegenerative disease.

In January, a coroner investigating the death of former Scotland and Manchester Utd centre-half Gordon McQueen said: "I am satisfied that, on the balance of probability, repeatedly heading footballs contributed to his developing chronic traumatic encephalopathy."

A field study by Glasgow University in 2019 found that former professional footballers were three-and-a-half times more likely to develop neurodegenerative disease. That figure was even higher for defenders.

"I actually looked, a few years ago, at the heading rates across World Cups, going all the way back to 1966," Dr Willie Stewart, who led the study, said.

"The stats actually showed that the amount of headers in games were increasing over that 50-year period, rather than declining, as some people might have thought - so I'm not too surprised."

In 2022, the Scottish FA introduced a number of changes aimed at minimising the risk.

Heading the ball was banned for under-12s and, in the professional game, there was a ban on heading the ball during training the day before and after a match.

Clubs were also told to limit training exercises that involve repeated heading to one session per week.

The SFA's chief medical officer Dr Jonny Gordon said: "The Scottish FA has led the way in research into head trauma in sport, working in partnership with the University of Glasgow in a landmark 2020 field study and additional research published in 2022.

"We will continue to monitor guidance based on evolving research as part of the association's commitment to ensuring the national game is a safe and enjoyable environment for all players."

It is also worth pointing out the huge health benefits associated with playing football.

Dr Stewart's study found that former professional players were much less likely to die of problems like cancer and heart disease.

So, why is it that the football spends more time in the air in Scotland?

Former defender Willie Miller played 560 times for Aberdeen and earned 65 caps for Scotland.

"The stats are a little surprising and I don't know what we're doing wrong," the BBC Radio Scotland Sportsound pundit said.

"One of the refreshing things this year has been watching Motherwell. They are not a tall team and constantly build up from the back and play a lot of good football.

"Maybe we need to work harder on the coaching side and I know the SFA has been doing some work on it with the youngsters, but clearly we have to turn the product round a bit for the good of the game and the health of the players as well."

Others who have played north and south of the border believe it could be a cultural issue.

"Yes, but I don't think it will ever change - it's just the Scottish culture," former Scotland and Hearts defender Christophe Berra suggested.

"I've seen it at Tynecastle when new managers come in and want to play the ball on the ground, but when it's not going well, the fans can get on your back and just want it in the box."

The science is still emerging and the risks are still being understood.

However, if heading the ball more often increases the danger then the country that has been at the forefront of finding out why - more than most - has a decision to make about how the game evolves.