Smoking Linked to Disease Activity, Severity in Ankylosing Spondylitis

BRIGHTON, ENGLAND – Patients with ankylosing spondylitis who currently smoke are likely to be headed for increased disease activity and worse quality of life outcomes.

The results of a cross-sectional, postal survey found that, compared with never smoking, current smoking is associated with higher levels of disease activity, worse functional status, greater pain and overall poorer quality of life.

This is the largest study to date to look at the effects of smoking on disease activity and severity and associated quality of life in ankylosing spondylitis (AS), according to the study’s authors.

"We know that smoking is a risk factor for rheumatoid arthritis ... and is associated with more severe disease and worse response to therapy," said Dr. Derek Mattey on April 13 at the annual meeting of the British Society for Rheumatology.

"The influence of smoking in AS is a lot less clear, however, and [until now] there have been no studies beyond susceptibility and very few studies on smoking as a risk for more severe disease," added Dr. Mattey of Keele University and the University Hospital of North Staffordshire, England.

Questionnaires were sent to 1,000 patients with AS registered at 10 secondary-care rheumatology practices in England. The questionnaire asked about smoking history and used several patient-reported outcome measures. These included the Bath AS disease activity and functional indices (BASDAI/BASFI); pain numeric rating scale (NRS); the AS quality of life questionnaire (ASQoL) and the evaluation of AS quality of life (EASi-QoL).

Data were looked at in terms of smoking status and in relation to the pack-year history. A pack-year is a means to quantify how much a person has smoked over a long time period. It is calculated by multiplying the number of packs smoked per day by the number of years smoked. The higher the pack-year, the longer the person has smoked.

Of 612 patients who responded, 606 provided information about their smoking history. The mean age of respondents was 50.8 years, 72% were male, and the mean disease duration was 17.2 years (standard deviation = 11.7 years). Around half of the cohort had never smoked, with approximately 28% reporting that they were past smokers and 21% saying that they were current smokers.

Mean BASDAI, BASFI, pain NRS, ASQoL, and EASi-QoL scores were all higher, indicating a worse outcome, in patients that had ever smoked, compared with never smokers. Significant, dose-dependent, correlations were also found between the number of pack-years and these disease outcome measures, with worse outcomes the higher the number of pack-years.

"We’ve shown that smoking has a dose-dependent relationship with measures of disease severity in AS," Dr. Mattey said. "High disease activity and more severe pain are most strongly associated with current smoking, while decreased function and poor quality of life are associated more closely with pack-year history."

All these associations appeared to be independent of age, sex, duration, and social deprivation level.

Commenting on the findings after their presentation, Dr. Deborah Symmons of the University of Manchester, England, said: "As this is a cross-sectional study, it is possible that correlation works in the opposite direction, in that people with more active disease and more pain find it more difficult to give up smoking."

Looking at the data longitudinally might be more appropriate, she suggested.

Dr. Mattey agreed that a reverse correlation was possible, but said that most of these patients started smoking before their disease started.

Dr. Mattey said that he had no conflicts of interest but noted that a coinvestigator, Dr. Jonathan Packham, had received an educational grant from Wyeth UK.