You're never too old to reap the health benefits of quitting smoking, a new study finds.
Predictors of mortality
"Even participants who quit smoking in their 60s were 23 percent less likely to die during follow-up than those who continued to smoke into their 70s," said lead researcher Sarah Nash, who conducted the study while at the US National Cancer Institute.
In addition, the age at which you start smoking can have an impact on longevity, the researchers found.
"This study confirms that age at smoking initiation and cessation, both key components of smoking duration, continue to be important predictors of mortality in US adults over age 70," Nash said.
"It also underscores the importance of measures to prevent initiation, as well as encourage cessation, for all smokers," she added. Nash is currently with the Alaska Native Epidemiology Centre at the Alaska Native Tribal Health Consortium in Anchorage.
Nash's team found that smoking, which is known to be an important predictor of early death among middle-aged smokers, was also strongly related to early death from smoking-related causes among those aged 70 and older.
Compared with those who had never smoked, people who still smoked when they were 70 and older were three times more likely to die during the six-year study period, Nash said.
Risk of death
In addition, among current smokers, the age at which they started smoking was linked to an increased risk of smoking-related death, Nash said. "Smokers who started smoking earlier in life were at increased risk of death, as were those who smoked more cigarettes per day over the age of 70," she said.
"Regardless of their age, all smokers benefit from quitting," Nash added. "Also, smoking patterns early in life may still affect mortality even 50 to 60 years later. So, it is important to support efforts to prevent adolescent smoking initiation."
The study findings were published in the American Journal of Preventive Medicine.
The study reinforces several well-known facts about smoking and the risk of death, said Dr Norman Edelman, a senior medical consultant to the American Lung Association.
Continuing smoking increases the risk of dying, because the risks of cancer, chronic obstructive pulmonary disease (COPD) and heart disease continue to increase as you keep smoking, he said.
Read: Smoking and cancer
"But the study also makes the point that I try to tell my patients, some of whom believe it and some of whom don't, that smoking cessation is good for you even late in life. If you stop, you will live longer than if you don't stop," Edelman said.
Follow-up of six years
For the study, Nash and her colleagues collected data on more than 160,000 men and women, aged 70 and older, who took part in a national health study. The participants completed a questionnaire about their smoking habits in 2004-2005. Deaths among the participants were tracked until the end of 2011.
Between 2014 and 2016, the researchers correlated age at death with the age when the participants started or stopped smoking.
Causes of death were also noted, including lung cancer and other smoking-related cancers (such as bladder, colon, oesophageal, head and neck, kidney and renal pelvis, liver, pancreatic and stomach cancers and acute myeloid leukaemia). Also assessed were deaths from heart disease, stroke, diabetes and respiratory diseases such as pneumonia, influenza and COPD.
The researchers also took age, gender, level of education and alcohol use into account.
At the start of the study, the average age of participants was 75. Nearly 56 percent were former smokers, and 6 percent were current smokers. Men were less likely (31 percent) to have never smoked than women (48 percent). Men smoked more than women, and men were more likely than women to have started smoking at age 15 (19 percent vs. 10 percent).
Over an average follow-up of six years, nearly 16 percent of the participants died. Among those who died, 12 percent had never smoked. Death rates increased among those who quit smoking at later ages: 16 percent for those who quit in their 30s, 20 percent if they quit in their 40s, 24 percent for those in their 50s, and 28 percent for those in their 60s, Nash's team found.
Current smokers fared worst of all, with 33 percent dying, Nash said. Death rates for women were lower than men at each age, she added.
Edelman said: "This study makes it clear that you can't hide behind the usual smokescreen [that] 'The damage has already been done, I may as well continue smoking.' If you quit smoking, you will add years to your life."