Smoking and its consequences: studies probe quitting, relapse and lung disease

Two adjacent posters at the Tenth International Congress on Drug Therapy in HIV Infection (HIV10) in Glasgow last week looked at smoking in people with HIV and at its most common consequence – not heart attacks or lung cancer but chronic obstructive pulmonary disease (COPD), a spectrum of respiratory disorders that can start off with persistent ‘smoker’s cough’ but end as emphysema, a frequently lethal degeneration of lung tissue.

Investigators from the Swiss HIV Cohort, which collects data on patients from seven Swiss HIV clinics, investigated smoking rates between 2000 and 2009 in 10,511 patients with HIV and compared them with rates in the general Swiss population. It also investigated the rates of giving up smoking (cessation) and starting again (relapse).

It found that smoking was at least 50% more common in people with HIV than in the general population. In the year 2000 approximately 60% of HIV-positive patients smoked in Switzerland, compared with approximately 38% of men in the general population and 27% of women.

Smoking prevalence declined over the next decade in both the general population and in the study patients, and in the HIV Cohort patients it declined somewhat faster than in the general population.

Amongst the general population, smoking declined by approximately 5% in both men and women between 2000 and 2009. In HIV-positive patients it declined by 16% to 43.5% by 2009. More women gave up than men, with nearly one in three female patients giving up during that time period, but only one in six men: smoking in men declined as fast as it did in women till 2005, but then slackened off to approximately the rate of decline in the general population.

The declines in smoking prevalence seen are, in individual terms, the sum total of people who managed to give up minus the total who re-started. The definition of cessation and relapse the researchers used was the same: the cessation rate was defined as the average number of people who were smoke-free for two consecutive clinic visits after they had been smokers for two consecutive visits. Relapse was defined as the opposite of this: two visits as a smoker after having not smoked for at least two visits.

The cessation rate in the HIV cohort was 4.4% a year and between 2000 and 2009 31% of patients gave up smoking at least once. This rate did not change throughout the decade. However, nearly half (44%) of these people restarted smoking at least once.

In injecting drug users (IDUs), who still form a significant part of the Swiss HIV-positive population, smoking rates were far in excess of other groups: 90% of IDUs smoked in 2000, declining to slightly over 80% in 2009.

IDUs also stopped smoking less often (one in ten ceased during the decade, compared with a third of heterosexual people and 40% of gay men) and relapsed more (55 versus 44%).

In a multivariate analysis controlling for age and sex, IDUs were just over 50% less likely to give up smoking than heterosexuals, and gay men 23% more likely: conversely IDUs were 41% more likely to relapse than either heterosexuals or gay men.

Respiratory symptoms and COPD

In a second study from Italy, researchers found that patients with HIV were much more likely to report cough, shortage of breath and respiratory symptoms in general than a group of HIV-negative controls of the same age. They also had nearly three times the rate of COPD.

Importantly, the HIV-negative control group contained the same proportion of smokers (57%) as the HIV-positive group, so these increases are not because people with HIV smoke more.

However, smokers were very much more likely to report symptoms than non-smokers.

Researchers from the University of Sassari investigated lung function and respiratory symptoms in eleven patients with HIV and 65 HIV-negative controls. The average age of both groups was 42. Seventy per cent of the positive group was male compared with 60% of the control group.

The HIV-positive group members were medically stable with an average CD4 count of 541 cells/mm³, and 71% had an undetectable viral load (although 35% had had an AIDS diagnosis in the past). Seventy-eight per cent were on antiretrovirals and only 10% had never taken them.Thirty-seven per cent of the HIV-positive group were current or former injecting drug users and the same proportion had hepatitis C.

The researchers found significantly lower lung function (forced expiratory volume, a measure of the lungs’ air-carrying capacity) in the positive patients.

They had much higher rates of respiratory symptoms of any kind than the control group (47 versus 15%), of cough (35 versus 14%), of difficulty breathing easily (30 versus 15%) and of diagnosed COPD (23.5 versus 7.5%). All these differences were statistically significant.

In multivariate analysis, people who had had former bacterial pneumonia were four times more likely to have respiratory symptoms than people who had not (people who had had PCP or other AIDS-related respiratory illness were excluded from the study, as were asthma sufferers).

Other than this, the only factor significantly associated with respiratory symptoms was current smoking, and overwhelmingly so: smokers were eleven times more likely to have respiratory symptoms and six times more likely to have COPD than non-smokers.

“HIV patients, especially smokers, should be regularly screened for respiratory disease,” the researchers concluded.