Abstract
BackgroundThe extent to which smoking contributes to adverse outcomes among men and women of all ages undergoing dialysis is uncertain. The objective of this study was to determine the differential impact of smoking on risks of mortality and kidney transplantation by age and by sex at dialysis initiation.MethodsWe conducted a population-based cohort of incident U.S dialysis patients (n = 1, 220, 000) from 1995–2010. Age- and sex-specific mortality and kidney transplantation rates were determined for patients with and without a history of cardiovascular disease. Multivariable Cox regression evaluated relative hazard ratios (HR) for death and kidney transplantation at 2 years stratified by atherosclerotic condition, smoking status and age. Analyses were adjusted for demographic characteristics, non-cardiovascular conditions, laboratory variables, socioeconomic and lifestyle factors.ResultsThe average age was 62.8 (±15) years old, 54 % were male, and the majority was white. During 2-year follow-up, 40.5 % died and 5.7 % were transplanted. Age- and sex-specific mortality rates were significantly higher while transplantation rates were significantly lower for smokers with atherosclerotic conditions than non-smokers (P < 0.01). The adjusted mortality hazards were significantly higher for smokers with pre-existing coronary disease (HR 1.15, 95 % CI (1.11–1.18), stroke (HR 1.21, 1.16–1.27) and peripheral vascular disease (HR = 1.21, 1.17–1.25) compared to non-smokers without these conditions (HR 1.00, referent group). The magnitude of effect was greatest for younger patients than older patients. Contrastingly, the adjusted risks of kidney transplantation were significantly lower for smokers with coronary disease: (HR 0.60, 0.52–0.69), stroke; (HR 0.47, 0.37–0.60), and peripheral arterial disease (HR 0.55, 0.46–0.66) respectively compared to non-smokers without these conditions.ConclusionsWe provide compelling evidence that smoking is associated with adverse clinical outcomes and reduced lifespans among dialysis patients of all ages and sexes. The adverse impact is greatest for younger men and women.Electronic supplementary materialThe online version of this article (doi:10.1186/s12882-016-0311-x) contains supplementary material, which is available to authorized users.
Highlights
The extent to which smoking contributes to adverse outcomes among men and women of all ages undergoing dialysis is uncertain
The aim of this study was to 1) explore the relative contribution of smoking with mortality among new dialysis patients with and without atherosclerotic cardiovascular disease, and 2) to examine the association of smoking with likelihood of kidney transplantation taking into consideration differences in demographic, comorbid characteristics and 3) to determine whether associations with these outcomes differed between men and women and across representative age groups
We found that the interaction between coronary disease and smoking with mortality was further modified by age and this was confirmed when a 3-way interaction term with age was included in the model
Summary
The extent to which smoking contributes to adverse outcomes among men and women of all ages undergoing dialysis is uncertain. The objective of this study was to determine the differential impact of smoking on risks of mortality and kidney transplantation by age and by sex at dialysis initiation. The extent to which these conditions contribute to elevated death risk is determined by the effectiveness of cardiovascular treatment strategies and the degree to which existing atherosclerotic risk factors are controlled [7, 8, 9]. Despite these facts, it is surprising that only few studies exist that have addressed the clinical significance of smoking, an established modifiable risk factor, on. Patients who smoke prior to kidney transplantation experience higher rates of graft loss, cardiovascular events and death [16,17,18,19,20]
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