Sunday 8 January 2012

It's never too late to quit smoking

NUS study finds risk of death is cut within five years of kicking habit
By Melissa Pang, The Straits Times, 7 Jan 2012

IT IS never too late to quit smoking.

This is a conclusion that has emerged in a National University of Singapore (NUS) study, which has gathered data to show that smokers - even long-term ones - can cut their risk of dying as soon as within five years of quitting the habit.

Their risk of dying of lung cancer is cut even more significantly.

The researchers from the university's Saw Swee Hock School of Public Health had set out to compare the short- and long-term effects of stubbing it out on mortality risk, specifically among middle-aged and elderly Chinese here.

Principal investigator Koh Woon-Puay said it is well known that one can cut one's risk of dying by kicking the smoking habit.

What was unknown was how quickly the benefits of stopping can be observed, especially among the elderly.

Associate Professor Koh said: 'Does a smoker need to have stopped for 10 years before he can see the benefits? Or does it start as soon as he puts down the cigarette?'

For the answer, the researchers turned to the Singapore Chinese Health Study, a cohort study of diet and health among middle-aged and elderly Chinese here, specifically Hokkiens and Cantonese for genetic homogeneity.

At the start of the survey between 1993 and 1998, there were 63,257 participants aged 45 to 74.

In their first or baseline interview, they were asked questions on their lifestyles and medical history and put into one of three groups - those who had never smoked, former smokers and current smokers.

Between 1999 and 2004, follow-up interviews were done with the remaining 48,251 participants. The others had died or were no longer contactable.

The remaining participants were reclassified into four groups:
- Current smokers - Those who said they were smoking, at both interviews;
- Long-term quitters - Those who reported having quit at the first interview and remained 'clean' in the follow-up;
- New quitters - Those who were smoking at the time of the first interview but had quit before the follow-up;
- Those who had never smoked.
Researchers then looked up information on participants who had died any time up to Dec 31, 2009, to examine the causes of death, and noted the group they were in. The results were telling:

The new quitters, that is, those who had quit for fewer than five years, were found to have a 76 per cent risk of lung cancer relative to current smokers.

Among the long-term quitters, those who had not smoked in the last 17 years, the risk level was 44 per cent.

In overall risk of death, new quitters had an 84 per cent risk relative to current smokers, but long-term quitters came out ahead at 61 per cent.

Less pronounced were the effects of smoking cessation on Chronic Obstructive Pulmonary Disease (COPD), a group of lung diseases that make it increasingly difficult for the patient to breathe.

New quitters were found almost equally at risk of dying of COPD as current smokers, possibly because the damage to their lungs may take years to reverse.

Prof Koh said the results showed that the benefits of smoking cessation can kick in as rapidly even in men and women over the age of 60.

She noted that the national campaign against smoking has been targeted mainly at young people. That they are the priority is as it should be when resources are limited, she said, 'but we hope more efforts can also be targeted at the elderly. There is concern that they may be unaware of the benefits of quitting'.

Figures from the 2010 National Health Survey showed that about 14 per cent of Singapore residents aged 18 to 69 years smoked cigarettes daily.

The habit is most prevalent in young adults aged 18 to 29 years and those aged 30 to 39 - about 30 per cent.

The 40 to 49 age group made up 14.5 per cent of daily smokers; those aged 50 to 59 made up 11 per cent, and those aged 60 to 69, 11 per cent too.

Researchers identify gene linked to lung cancer
By Feng Zengkun, The Straits Times, 7 Jan 2012

SCIENTISTS may have found a breakthrough in the fight against lung cancer.

They have identified a gene which could be responsible for 85 per cent of all lung cancer cases. Tests showed that switching off the gene causes the tumour to shrink.

It is not the first gene to be associated with the cancer but it may be the most significant to date.

The research, a collaboration between the Genome Institute of Singapore at the Agency for Science, Technology and Research, and local hospitals and schools, was published in the online edition of science journal Cell on Thursday.

In Singapore, lung cancer is the second-most common cancer among men and the third-most common among women.

The scientists discovered the gene by screening about 300 tumour samples from patients. They sorted cells in the tumours according to markers which had previously been shown to identify cancer stem cells. These are cells which can grow into different types of cells and scientists believe they remain unharmed during chemotherapy and can lead to relapses.

Cells which were positive for CD166, a marker, for example, were sorted into a different basket from those which tested negative for the marker.

The positive and negative cells were then implanted into animals to see if lung-cancer tumours were associated with the marker.

Out of the six markers, only one, CD166, showed a significant difference between the positive and negative cells. Animals with the positive cells grew tumours whereas those with the negative cells did not.

The scientists compared the CD166 positive and negative cells to find genes that appeared in much higher quantities in the positive cells.

About 100 genes were identified, with glycine decarboxylase, or GLDC, at the top of the list. For each of the top 10 genes, the scientists reduced its volume in the cancer cells to see if this had any effect on the tumours.

Cutting the amount of GLDC led to the tumours becoming smaller whereas no such effect was seen for the other genes.

To verify the effect of GLDC, the scientists increased its volume in normal cells and the move made them cancerous.

GLDC is usually found in normal cells at low amounts that do not cause any harm. The scientists said it is not known what causes the number of GLDC genes to increase to a dangerous level.

They found high levels of GLDC in all the sample cases of adenocarcinoma, which makes up about 60 per cent of all lung cancer cases and affects mainly Asian non-smokers.

The gene was also found at higher levels in several samples of squamous cell lung cancer, which makes up 25 per cent of cases, but the scientists said more studies need to be done.

The remaining 15 per cent of cases are of small cell lung cancer, on which there is no research related to GLDC.

Project leader Lim Bing, GIS' associate director of cancer stem cell biology, said a higher level of GLDC could lead to cancer because the gene helps to create building blocks for DNA. Cancer is caused by cells multiplying out of control.

He said the team's next step is to figure out the exact relationship between GLDC and cancer. The scientists may also investigate GLDC's role in other cancers such as ovarian and breast.

Dr Lewis Cantley, a professor of cell biology at Harvard Medical School, said GLDC does not appear to be required for the growth of normal adult tissues.

'These results raise the possibility that this (gene) could be a target for cancer therapy,' he said.

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