MELBOURNE: Older, overweight scuba divers are being urged to shed pounds to avoid an underwater heart attack, by scientists who found that cardiac ailments are one of the leading causes of diving-related deaths.
From 1989 to 2015, the proportion of diving fatalities involving 50-59 year-olds increased steadily from 15 to 35 per cent, while fatalities in the over-60s soared from five to 20 per cent.
Cardiac events are now the second leading cause of death behind drowning.
People who pay to go diving must learn skills and theory and be screened for fitness.
But, after that initial screening, certification to scuba dive lasts for life.
"It's not commonly new divers who have health problems, because they have been recently screened.
It is older divers who have not looked after their health," said Peter Buzzacott, of the University of Western Australia.
"Divers who learned to dive years ago and who are now old and overweight, with high blood pressure and high cholesterol, are at increased risk of dying," said Buzzacott.
Until now there has been no clear picture of how common cardiovascular risk factors are among active divers.
Previous research has been limited to surveys of dive club members or insured divers.
This was the first study conducted among divers in the general population.
The researchers used data from the Behavioral Risk Factor Surveillance System (BRFSS), a telephone survey conducted by the US Centers for Disease Control and Prevention (CDC).
Scuba diving was included as an activity in the 2011, 2013, and 2015 surveys.
The three surveys represent nearly 736 million people, of whom around 498 million (68 per cent) had been active in the previous month and, for 113,892 people (0.
02 per cent), their principal activity was scuba diving.
This analysis compared the 113,892 scuba divers with a group of 338,933 active people matched for age, sex, and state of residence whose main activity was not scuba diving.
The data shows that one-third of scuba divers are aged 50 years or older.
They are often well educated, more than half earn at least USD 75,000 a year, and most are married with children.
A significantly greater proportion of divers (54 per cent) had smoked cigarettes at some point compared with non-divers (46 per cent) but more divers had given up smoking (40 per cent versus 26 per cent).
Divers were more frequently overweight (48 per cent versus 43 per cent) but had lower mean body mass index overall than the non-divers.
One-third of divers had been diagnosed with high blood pressure and 30 per cent had high cholesterol - levels that were not statistically different from the comparison group.
Researchers advised all divers to have routine fitness assessments with their doctor, and tackle risk factors that otherwise could lead to a fatal cardiac event while diving.
"Never before in history have so many people been exposing themselves to these extraordinary environmental stresses and, for the first time ever, we now have a large number of people who have spent their entire lives regularly scuba diving," said Buzzacott.