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BackgroundAlthough it has been widely accepted that smoking has a negative effect on AS and aSpA patients, the findings were limited by small sample size and conflicting data.ObjectivesTo examine the impact of smoking on clinical and structural damage in patients with AS and aSpA.MethodsA systematic literature review was performed by 2 reviewers, a librarian and a methodologist. Studies were identified by a sensitive search strategies in the main bibliographic databases (Medline, Embase and Cochrane Library) up to November 2014. We selected articles that analysed, in AS and aSpA patients, the smoking impact on disease activity, structural damage, functional status and quality of life. Any type of study except case series or case reports was eligible. Two reviewers (VVG and TCI) screened the titles and abstracts of the retrieved articles independently. VVG reviewed the selected articles in detail and collected the data from the studies included by using ad hoc standard forms. A hand research was completed by reviewing the included studies references. The evidence level was assessed with the Oxford Centre for Evidence-based Medicine Levels of Evidence.ResultsOf 341 studies identified, 13 were selected for inclusion: 7 case-control and 6 cohort studies. These studies provided data from over 4.163 patients. All studies evaluated patients with AS and only two evaluated patients with AS and aSpA, being the quality of the studies moderate-low. Current smokers with AS, had a higher disease activity (BASDAI >4) [OR=1.83; IC95% 1.13 a 2.98; p=0.015], poorer quality of life (ASQoL>7) [OR=2.00, IC95% 1.25 a 3.22, p=0.004] and more pain (numerical scale NRS) [OR=2.00, IC95% 1.23 a 3.27, p=0.005], independently of age, sex, duration of the disease and social support. Smoking was significantly associated with progression of functional disability in patients with AS for less than ten years of disease duration (HAQ-S increased 0.0545 units/yr among smokers compared to nonsmokers, p=0.004).In patients with aSpA, smoking was associated with an earlier onset of inflammatory back pain [regression coefficient (B)= -1.46; IC 95% -2.87 a -0.06, p=0.04], higher disease activity (ASDAS-PCR B=0.20; IC95% 0.02 a 0.38; p=0.03; BASDAI B=0.50; IC95% 0.17 a 0.83; p=0.003), worse functional status (BASFI B=0.38; IC95% 0.07 a 0.69; p=0.02), more frequent inflammation and more structural damage in MRI (OR=1.91; IC95% 1.34 a 2.72, p<0.001) and plain radiography (OR=1.56; IC95% 1.08 a 2.26, p=0.02), and poorer quality of life (Euro-QoL) [B=1.38; IC95% 0.69 a 2.07, p<0.001].ConclusionsSmoking cessation should be recommended in AS and aSpA patients, not only at the disease onset, but also along the follow-up. However, the available evidence is insufficient and limits the recommendation strength (NE 4, GR C). Larger-scale studies with longitudinal follow-up in disease activity, functional ability and structural damage in AS and aSpA patients, are necessary.This systematic literature review was performed to inform the aSpA and psoriatic arthritis guideli...