The more adversities people face, the more likely they are to start smoking and the less likely they are to quit, a US study suggests.
Researchers examined data from a decade of annual national surveys, focusing on 278,048 adults who were asked about smoking as well as six socioeconomic or health-related disadvantages: unemployment, poverty, low education, disability, serious psychological distress and heavy drinking.
About 14 per cent of people without any of these forms of adversity smoked, researchers report in JAMA Internal Medicine.
With each added disadvantage, smoking rates climbed, rising to 58 per cent among people with all six forms of adversity.
Similarly, for people with no disadvantages, or just one or two forms of adversity, smoking odds declined each year from 2008 to 2017, the study found. Smoking odds were unchanged over time, however, among people with three or more disadvantages.
"Our study makes the striking discovery that a variety of types of disadvantages, spanning poverty, being disabled, having mental illness, and others - each of which are very different from one another - all add up to the same outcome: they increase your risk of smoking," said lead study author Adam Leventhal, director of the University of Southern California Health, Emotion & Addiction Laboratory.
Nationwide, smoking has become less common in recent years, Leventhal said by email. But nearly all of the decline is concentrated among people with few if any disadvantages.
"Disadvantage is a common denominator in smoking in the US today, and if you face more disadvantages, your liability to smoking increases," Leventhal said. "Disparities in smoking are explained by disadvantaged populations being more likely to start smoking and less likely to quit smoking."
While almost 21 per cent of participants reported one disadvantage, many experienced more than one. Almost 9 per cent had two disadvantages; 4 per cent reported three disadvantages; 1.6 per cent had four disadvantages; 0.04 per cent had five or six.
Disability was the most common form of disadvantage in the study, experienced by roughly one in five survey participants.
Poverty and limited education were also common, each experienced by 13 per cent of people in the study.
Almost 8 per cent of participants were unemployed. Slightly less than 4 per cent had serious psychological distress and 2.6 per cent were heavy drinkers.
One limitation of the study is that it didn't examine how much people smoked or what types of nicotine products they used. It's also possible that brief behavioural health measures in the survey didn't capture everyone with mental health problems or substance use disorders that are associated with smoking.
"Smoking rates are higher among people with lower educational attainment and income, and also among people with mental health concerns like depression or substance use disorders," said Stephanie Mayne of the Children's Hospital of Philadelphia and the Perelman School of Medicine at the University of Pennsylvania.
"Smokers with lower socioeconomic status are just as likely to attempt to quit smoking as those with higher socioeconomic status, but are less likely to succeed in quitting, so disparities have widened over time," Mayne, who wasn't involved in the study, said by email.
While it's not fully clear what it is about each of these risk factors that operates to increase risk, a greater understanding of these risks could be help doctors tailor smoking cessation support to the types of disadvantages individual patients may experience, said Eric Leas, a researcher at the University of California, San Diego who wasn't involved in the study.
"For instance, a smoker who is trying to quit smoking and has two of the risk factors - e.g. they have psychological distress and are below the poverty line - could potentially be assigned something to help with psychological distress and something to help them pay for treatment while they try to quit smoking," Leas said by email.
"If you are a patient trying to quit smoking, identifying and addressing factors that make it challenging for you to quit smoking (e.g., psychological distress, drinking heavily or difficulty paying for treatment) could be a step in improving your ability to quit successfully," Leas added.