Genetic discovery may help smokers

By SIMON COLLINS science reporter

Doctors at Auckland's Green Lane Hospital have found four genetic changes which make smokers more likely to develop crippling breathlessness.

The researchers say one-third of smokers have all four genetic mutations and two-thirds of those people will get emphysema or bronchitis.

The discovery will not help people who already have emphysema such as Mt Wellington invalid beneficiary Helen Scott, who had to stop fulltime work at the age of 48.

But it means that other smokers can now find out whether they have the four mutations and may be able to stop smoking in time to stave off the worst effects.

"Smokers at risk would lose the traditional excuse of, 'it won't happen to me'," said Dr Robert Young, an Auckland Medical School lecturer who led the research team.

Mrs Scott, who carries an oxygen tank connected to her nose and has to stop for breath after walking a few metres to the letterbox, said she was shocked when she suddenly woke up one morning in 1990 and could not breathe.

"I didn't even have a doctor in Auckland. I had never been sick," she said.

But by the time she found she could not breathe, she had already lost about half of the normal function of her lungs.

Dr Young started his career looking for a genetic cause of asthma, but switched the search to genes affecting breathing in smokers after working in Hong Kong for five years in the 1990s.

"I have spent the best part of 15 years treating people who are chronically and profoundly breathless," he said. "I see them gasping, but we can do very little for them."

Emphysema, bronchitis and other long-term breathing diseases affect 5 per cent of all New Zealanders over the age of 40 and 20 per cent of smokers. More than 500 people die in agonising breathlessness each year.

The diseases are almost entirely confined to smokers.

"If you don't smoke, your risk of developing chronic obstructive pulmonary disease [COPD] is exceedingly small, if not zero," Dr Young said.

But despite millions of dollars spent on anti-smoking campaigns, the proportion of adults who smoke has dropped only from 30 per cent to 23 per cent in the past 20 years. The Maori rate (51 per cent) is higher than in Turkey (47 per cent), which has the highest rate of any developed country.

Dr Young hopes his genetic test will finally give some smokers the stimulus they need to kick the habit.

One of the four genetic mutations that made smokers susceptible to developing emphysema and bronchitis had also been found independently by Canadian researchers.

"The other three are completely novel findings," he said.

Most overseas researchers in the field have looked for genetic mutations that run in families with high rates of lung diseases.

Dr Young's team looked instead for mutations that occurred in 180 smokers with COPD and not in a further 150 smokers without the disease.

The team also checked for the mutations in 200 healthy blood donors. The "normal" mutation rates ranged from 5 per cent for some mutations up to 40 per cent for others, with one-third of the smokers having all four mutations.

Two-thirds of the smokers with all four mutations developed COPD, compared with only 15 per cent of the smokers without the mutations.

The team has received $424,702 from the Health Research Council to test a further 1500 smokers with and without COPD in Auckland and Christchurch.

If the genetic test proves robust, Dr Young hopes it will be available to smokers within 12 to 14 months.

The president of the Thoracic Society of Australia and New Zealand, Middlemore clinical director of medicine Dr Jeff Garrett, said he doubted that many smokers would pay for the test because they would still risk getting lung cancer or heart disease even if they were not susceptible to COPD.

But he said the test would be of international interest as a way of narrowing down the search for enzymes or antioxidants in the lung which made some people more susceptible to lung diseases.

Deadly disease

* Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the developed world and kills 2.9 million people a year.

* It is the most common and disabling complication of smoking, sufferers progressively lose lung function to the point where just getting up or moving around the house will cause breathlessness.