Cigarette Smoking in Renal Transplant Recipients

Cigarette Smoking in Renal Transplant Recipients J Am Soc Nephrol 11: 753 759, 2000 BERTRAM L. KASISKE and DAGMAR KLINGER Department of Medicine, Division of Nephrology, Hennepin County Medical Center, Minneapolis, Minnesota. Abstract. Cigarette smoking increases the risk for cancer and cardiovascular disease in the general population, but the effects of smoking in renal transplant recipients are unknown. The effects of smoking were investigated among patients transplanted at Hennepin County Medical Center between 1963 and 1997. Information on smoking was available in 1334 patients. The 24.7% prevalence of smoking at the time of transplantation was similar to that in the general population. After adjusting for multiple predictors of graft failure, smoking more than 25 pack-years at transplantation (compared to smoking less than 25 pack-years or never having smoked) was associated with a 30% higher risk of graft failure (relative risk 1.30; 95% confidence interval [CI], 1.04 to 1.63; P 0.021). Having quit smoking more than 5 yr before transplantation reduced the relative risk of graft failure by 34% (relative risk 0.66; 95% CI, 0.52 to 0.85; P 0.001). The increase in graft failure was due to an increase in deaths (adjusted relative risk 1.42; 95% CI, 1.08 to 1.87; P 0.012). The relative risk for major cardiovascular disease events with smoking 11 to 25 pack-years at transplant was 1.56 (95% CI, 1.06 to 2.31; P 0.024), whereas that of smoking more than 25 pack-years was 2.14 (95% CI, 1.49 to 3.08; P 0.001). The relative risk of invasive malignancies was 1.91 (95% CI, 1.05 to 3.48; P 0.032). Smoking had no discernible effect on the rate of return to dialysis or on serum creatinine during the first year after transplantation. Thus, cigarette smoking is associated with an increased risk of death after renal transplantation. The effects of smoking appear to dissipate 5 yr after quitting. These results indirectly suggest that greater efforts to encourage patients to quit smoking before transplantation may decrease morbidity and mortality. Cigarette smoking increases the risk for cancer and cardiovascular disease in the general population (1,2). Smoking also may have adverse effects on renal function (3). Therefore, it is likely that cigarette smoking may be particularly deleterious in renal transplant recipients who are already at high risk for cancer, cardiovascular disease, and renal allograft dysfunction. However, surprisingly few studies have examined cigarette smoking and its consequences after renal transplantation. Therefore, we examined the prevalence and clinical correlates of cigarette smoking in a large cohort of renal transplant recipients. Materials and Methods Patient Population We reviewed the clinical records of all 1500 transplants performed between February 13, 1963, and July 22, 1997, at Hennepin County Medical Center. All patients were eligible for at least 12 mo of follow-up. Smoking History We determined whether patients had a history of smoking at the time of transplant ( current smoking history), whether they had smoked within 5 yr of transplant, but not at the time of transplant ( recent smoking history), or whether they had smoked previously, Received July 8, 1999. Accepted September 13, 1999. Correspondence to Dr. Bertram L. Kasiske, Division of Nephrology, Department of Medicine, Hennepin County Medical Center, 701 Park Avenue, Minneapolis, MN 55415. Phone: 612-347-5871; Fax: 612-347-2003; E-mail: kasis001@tc.umn.edu 1046-6673/1104-0753 Journal of the American Society of Nephrology Copyright 2000 by the American Society of Nephrology but not for at least 5 yr before transplantation ( remote smoking history). We also estimated the total number of packs (20 cigarettes per package) smoked per day for each year before the time of transplantation ( pack-years at transplant). At least some information concerning smoking history was available in 1334 patients. In 1233 cases there were adequate records to estimate the total number of pack-years smoked at the time of transplantation. Other Variables Variables that we examined included: recipient age, gender, race/ ethnicity (Caucasian, African-American, Native American, Asian, Hispanic, and other), body weight, height, body mass index (weight in kilograms divided by height in meters-squared), body surface area, cause of renal failure (type 1 or 2 diabetes, primary glomerulonephritis, nephrosclerosis including hypertension and renovascular disease, polycystic kidney disease, systemic lupus erythematosus, and other), total duration of end-stage renal disease before transplant, and previous transplants. Comorbid indicators from the time of transplant included: history of ischemic heart disease (myocardial infarction and/or revascularization procedures), history of cerebral vascular disease (transient ischemic attacks and strokes), history of peripheral vascular disease (revascularization procedures and amputations), and history of invasive malignancy. Donor factors included source (cadaveric, living-related, and emotionally related), age, gender, and race. In addition, we included the number of previous transplants, major histocompatibility mismatches (A, B, and DR), the percent panel-reactive antibody status at peak and at transplant, whether splenectomy and/or bilateral nephrectomy had been performed before transplant, and the number of blood transfusions before transplant. We also tabulated the type of initial prophylactic immunosuppression that was used: Minnesota antilymphocyte globulin (MALG; University of Minnesota, Minneapolis, MN), antithymocyte globulin (ATG, or ATGAM; Upjohn, Kalamazoo MI), cyclosporin A (CsA, Sandimmune or Neoral; Novartis, Basel, Swit-

754 Journal of the American Society of Nephrology J Am Soc Nephrol 11: 753 759, 2000 zerland), mycophenolate mofetil (Cellcept; Roche, Nutley, NJ), azathioprine (Imuran; Upjohn, Kalamazoo, MI), and/or corticosteroids. We also tabulated the presence or absence of delayed graft function requiring dialysis within the first posttransplant week and the number of dialysis treatments that were needed. Outcomes we examined included: graft failure (death or return to dialysis), death, development of life-threatening cancer (exclusive of in situ malignancies, e.g., noninvasive squamous cell skin cancer or cervical carcinoma), major ischemic heart disease events (myocardial infarction, revascularization procedures, or death due to ischemic heart disease), cerebral vascular disease (transient ischemic attacks or strokes), and peripheral vascular disease (amputations or revascularization procedures). In a subset of patients surviving with a functioning graft for at least 1 yr, we also collected data on posttransplant total cholesterol and systolic BP. For cholesterol and BP, we used the average of values from 3, 6, and 12 mo posttransplant. To adjust for time trends, we used indicator variables defining immunosuppression eras during which patients underwent transplantation. These included: (1) the pre-malg era (before January 1969); (2) the pre-csa era (January 1969 through December 1985); (3) the CsA era (from January 1986 through August 1992); and (4) the post-malg era (after August 1992) when MALG was withdrawn. The MALG used for induction was initially replaced with ATG, and then replaced with a CsA-induction protocol. During this latter era, mycophenolate mofetil replaced azathioprine. Statistical Analyses We examined differences between group means using ANOVA or t test for continuous variables, and a 2 test for differences in categorical data. We examined the effects of smoking on survival using Kaplan Meier plots and the log-rank test for differences. We also carried out multivariate Cox proportional hazards analysis to examine the independent effects of smoking on outcomes. In the multivariate analysis, we included interaction terms to examine possible interactions between the cumulative number of pack-years smoked and having nevertheless quit smoking more than 5 yr before transplantation. To include all events that occurred posttransplant in the multivariate survival analysis, we used only variables known at the time of transplantation or, in the case of delayed graft function, discovered immediately posttransplant. Differences were considered significant at P 0.05. Results are displayed as means and 95% confidence intervals [CI]. Results Prevalence of Cigarette Smoking Of the 1334 patients for whom there was adequate information, 24.7% smoked at the time of transplant, 18.4% quit more than 5 yr before transplant, 10.9% quit within 5 yr of transplantation, and 46.0% had never smoked. Of the 612 who gave a history of smoking, the number of pack-years was 23.5 (95% CI, 21.8 to 25.3). The number of pack-years was 22.7 (95% CI, 19.5 to 25.9) for the 206 who had quit more than 5 yr pretransplant, 30.8 (95% CI, 25.8 to 35.8) for those who had quit within 5 yr of transplant, and 20.9 (95% CI, 18.9 to 22.9) for those who still smoked at the time of transplant (P 0.001). The prevalence of cigarette smoking was comparable to what has been observed in the United States and in Minnesota (Tables 1 and 2). Table 1. Smoking prevalence by era a Year United States (%) 1965 42.4 1966 42.6 1970 37.4 1974 37.1 1978 34.1 1979 33.5 1980 33.2 1983 32.1 Transplant 33.5% (66 of 197) 33.6% (87 of 259) 1985 30.1 1987 28.8 20.7% (66 of 319) 1988 28.1 1990 25.5 1991 25.7 1992 26.5 1993 25.0 26.1% (37 of 142) 19.9% (29 of 146) 1994 25.5 16.2% (17 of 146) a Data are from the Centers for Disease Control and Prevention (14). The numbers and percents correspond to the time interval indicated in the first column. For example, the prevalence of smoking in the United States in 1965 was 42.4%; in Minnesota it was 33.5% between 1965 and 1979. Table 2. Smoking prevalence by age a Age (yr) Minnesota 1992 1993 Transplant 1990 1997 25 to 44 27.1% 25.7% (63 of 245) 45 to 64 20.8% 16.8% (36 of 214) 65 9.2% 11.1% (7 of 63) a Data are from Centers for Disease Control and Prevention (www.cdc.gov/tobacco/statehi/htmltext/mn_sh.htm). Characteristics of Patients Who Smoked There were differences in age, race, gender, the proportion with renal disease from diabetes, and the transplant era for patients who smoked, did not smoke, or had smoked and quit before transplantation (Table 3). Those who smoked at the time of transplantation compared to those who did not were younger (38.7 yr [37.4 to 40.0] versus 43.3 yr [42.5 to 44.1], P 0.001), more likely to be black (8.2% versus 2.2%, P 0.001), less likely to have renal disease caused by type 2 diabetes (4.6% versus 10.0%, P 0.002), and more likely to have been transplanted before August 1992 (30.3% versus 18.5%, P

J Am Soc Nephrol 11: 753 759, 2000 Cigarette Smoking in Renal Transplant Recipients 755 Table 3. Characteristics of patients who smoked a Characteristic Never Smoked Remote Smoker Recent Smoker Current Smoker P Value n (%) 613 (46.0) 246 (18.4) 146 (10.9) 329 (24.7) Age at transplant (years, 95% CI) 40.9 (39.8 to 42.0) 48.7 (47.2 to 50.3) 44.2 (42.2 to 46.3) 38.7 (37.4 to 40.0) 0.001 Posttransplant total 250 (246 to 255) 259 (252 to 267) 260 (249 to 271) 249 (243 to 255) 0.055 cholesterol (mg/dl, 95% CI) Posttransplant systolic BP 139 (137 to 140) 142 (140 to 144) 140 (138 to 143) 138 (136 to 140) 0.021 (mmhg, 95% CI) Male (n 778 of 1334) 52.7/41.5 b 65.4/20.7 b 70.5/13.2 b 58.1/24.6 b 0.001 Black race (n 49 of 2.0/24.5 b 2.4/12.2 b 2.7/8.2 b 8.2/55.1 b 0.001 1334) Type 1 diabetes mellitus 19.7/52.2 b 9.8/10.3 b 21.2/13.4 b 17.0/24.1 b 0.003 (n 232 of 1334) Type 2 diabetes mellitus 7.7/40.5 b 15.4/32.8 b 11.0/13.8 b 4.6/12.9 b 0.003 (n 116 of 1334) Transplant pre-8/92 31.2/52.2 b 32.9/22.1 b 22.6/9.0 b 18.5/16.7 b 0.001 (n 968 of 1334) Pretransplant IHD (n 95 of 1334) 5.4/34.7 b 10.6/27.4 b 8.2/12.6 b 7.3/25.3 b 0.058 a CI, confidence interval; IHD, ischemic heart disease. For all rows total n 1334, except for posttransplant cholesterol (n 1121) and posttransplant systolic BP (n 1156). b Numbers are percents of column/row; for example, 52.7% of those who never smoked were male and of the males, 41.5% never smoked. 0.001). There were no major differences in total cholesterol or systolic BP in those who smoked, did not smoke, or had smoked and quit at some time before transplantation (Table 3). Posttransplant cholesterol was 249 mg/dl (95% CI, 243 to 255) versus 254 mg/dl (95% CI, 250 to 258) for the 274 patients with cholesterol values who did, and the 847 who did not smoke at the time of transplantation, respectively (P 0.172). Posttransplant systolic BP was 138 mmhg (95% CI, 136 to 140) versus 140 mmhg (95% CI, 139 to 141) for the 286 patients with BP readings who did and the 870 who did not smoke at the time of transplant, respectively (P 0.140). Outcomes Associated with Cigarette Smoking While smoking per se was associated with increased mortality and decreased graft survival, the total number of packyears smoked at the time of transplantation was a stronger predictor of outcomes. In univariate analysis, smoking more than 25 pack-years at transplantation was associated with increased graft failure and higher mortality (Figures 1 and 2). After adjusting for multiple predictors of graft failure, smoking more than 25 pack-years (compared to smoking less than 25 pack-years or never having smoked) was associated with a 30% higher risk of graft failure (Table 4). This was abrogated largely by having quit more than 5 yr before transplantation, which reduced the relative risk by 34% (Table 4). These effects appeared to be additive, i.e., there was no interaction between the number of pack-years smoked and having quit 5 yr before transplant. Most of the effects of smoking on graft survival seemed to be due to its effects on mortality (Table 5). In contrast, smoking had no statistically significant effect on patients returning to dialysis. Indeed, after adjusting for the same variables shown in Table 5, the relative risk of returning to dialysis with smoking 1 to 10 pack-years (compared to 0 pack-years at transplant) was 1.35 (95% CI, 0.97 to 1.87; P 0.071); with 11 to 25 pack-years it was 1.07 (95% CI, 0.74 to 1.55; P 0.702) and with greater than 25 pack-years it was 1.01 (95% CI, 0.74 to 1.66; P 0.616). In addition, we could discern no effect of smoking on serum creatinine for patients who survived with a functioning graft during the first posttransplant year. For example, the average serum creatinine at 3, 6, and 12 mo was 1.56 mg/dl (95% CI, 1.50 to 1.61) for patients smoking no more than 25 pack-years at transplant, and 1.55 mg/dl (95% CI, 1.44 to 1.65) for patients smoking more than 25 pack-years at transplant (P 0.886). Smoking more than 25 pack-years at the time of transplantation was associated with an increased risk of cardiovascular disease (n 207 events) after adjusting for multiple risk factors in a multivariate analysis (Table 6). Specifically, the adjusted relative risk for ischemic heart disease (n 159 events) with smoking 1 to 10 pack-years (compared to 0 pack-years at transplant) was 0.90 (95% CI, 0.53 to 1.52; P 0.686); with 11 to 25 pack-years it was 1.68 (95% CI, 1.09 to 2.59; P 0.018) and with greater than 25 pack-years it was 2.05 (95% CI, 1.36 to 3.09; P 0.001). Similarly, the adjusted relative risk for cerebral vascular disease (n 75 events) with smoking 1 to 10 pack-years was 1.36 (95% CI, 0.70 to 2.66;

756 Journal of the American Society of Nephrology J Am Soc Nephrol 11: 753 759, 2000 Figure 1. The effects on graft survival of smoking more than 25 pack-years at the time of transplantation (n 207) compared to smoking 25 pack-years or less and never having smoked (n 1026). Figure 2. The effects on mortality of smoking more than 25 pack-years at the time of transplantation (n 207) compared to smoking 25 pack-years or less and never having smoked (n 1026). P 0.369); with 11 to 25 pack-years it was 1.29 (95% CI, 0.64 to 2.61; P 0.470) and with greater than 25 pack-years it was 1.88 (95% CI, 1.00 to 3.55; P 0.052). Unlike what was found for graft failure and mortality, having quit smoking more than 5 yr before transplantation did not significantly reduce the risk of cardiovascular disease. Cigarette smoking was also associated with an increased risk for 71 invasive malignancies, and having quit smoking more than 5 yr before transplantation did not reduce the risk of cancer (Table 7). The adjusted relative risk for lung neoplasms (n 11) with smoking 1 to 10 pack-years was 1.13 (95% CI, 0.10 to 12.71; P 0.922); with 11 to 25 pack-years it was 1.32 (95% CI, 0.12 to 14.71; P 0.821) and with greater than 25 pack-years it was 8.48 (95% CI, 1.64 to 43.92; P 0.011). In contrast, smoking had no statistically significant effect on non-lung malignancies. The adjusted relative risk for non-lung

J Am Soc Nephrol 11: 753 759, 2000 Cigarette Smoking in Renal Transplant Recipients 757 Table 4. Effects of cigarette smoking on graft failure a Smoked 1 to 10 pack-years at transplant 1.06 0.83 to 1.34 0.6541 Smoked 11 to 25 pack-years at transplant 1.12 0.87 to 1.42 0.3772 Smoked 25 pack-years at transplant 1.30 1.04 to 1.63 0.0206 Quit smoking 5 yr pretransplant 0.66 0.52 to 0.85 0.0009 Age 45 to 60 yr at transplant 1.44 1.16 to 1.77 0.0008 Age 60 yr at transplant 1.83 1.39 to 2.40 0.0001 Renal disease from type 1 diabetes mellitus 1.35 1.08 to 1.69 0.0077 Renal disease from type 2 diabetes mellitus 1.66 1.23 to 2.23 0.0008 Pre-Minnesota ALG era (before 1/69) 7.99 2.52 to 25.3 0.0004 Cadaveric kidney 2.28 1.71 to 3.05 0.0001 Two or more prior transplants 2.06 1.16 to 3.67 0.0140 Delayed graft function 1.21 1.03 to 1.43 0.0195 CsA used at transplant 0.80 0.67 to 0.95 0.0121 a Cox proportional hazards model, n 1233, overall P 0.0001. ALG, antilymphocyte globulin; CsA, cyclosporin A. Reference group (relative risk 1.00) either never smoked or if smoked failed to quit more than 5 yr before transplant, age 45, renal disease not caused by diabetes, transplanted after 1/69, living donor kidney, at most one prior transplant, no delayed graft function, and CsA not used at transplant. Table 5. Cigarette smoking and mortality a Smoked 1 to 10 pack-years at transplant 0.82 0.58 to 1.16 0.2693 Smoked 11 to 25 pack-years at transplant 1.16 0.84 to 1.61 0.3640 Smoked 25 pack-years at transplant 1.42 1.08 to 1.87 0.0119 Quit smoking 5 yr pretransplant 0.71 0.52 to 0.97 0.0304 Age 45 to 60 yr at transplant 2.79 2.09 to 3.72 0.0001 Age 60 yr at transplant 4.35 3.08 to 6.13 0.0001 Renal disease from type 1 diabetes mellitus 2.53 1.86 to 3.44 0.0001 Renal disease from type 2 diabetes mellitus 2.03 1.45 to 2.83 0.0001 Pre-Minnesota ALG era (1/69) 8.02 1.10 to 58.5 0.0401 Cadaveric kidney 1.87 1.30 to 2.70 0.0008 Delayed graft function 1.30 1.05 to 1.61 0.0162 CsA used at transplant 0.69 0.54 to 0.87 0.0019 a Cox proportional hazards model, n 1228, overall P 0.0001. Abbreviations as in Tables 3 and 4. Reference group (relative risk 1.00) either never smoked or if smoked failed to quit more than 5 yr before transplant, age 45, renal disease not caused by diabetes, transplanted after 1/69, living donor kidney, no delayed graft function, and CsA not used at transplant. neoplasms (n 60) with smoking 1 to 10 pack-years was 0.96 (95% CI, 0.46 to 2.03; P 0.925); with 11 to 25 pack-years it was 1.05 (95% CI, 0.51 to 2.19; P 0.889) and with greater than 25 pack-years it was 1.37 (95% CI, 0.69 to 2.73; P 0.372). Discussion The prevalence of cigarette smoking in our cohort of transplant recipients resembles that seen in the general population (Tables 1 and 2). It is encouraging that the prevalence of smoking at the time of transplantation has declined over the past 30 yr. Although the number of transplant patients in this study is relatively small, it appears that the prevalence of smoking in recent years may be slightly lower in transplant recipients compared to the general population (Table 1). Cigarette smoking at the time of transplantation was associated with increased graft failure, which, in turn, was largely due to increased mortality. A fatalistic interpretation of these results might be that it is too late to improve posttransplant outcomes by exhorting transplant candidates to quit smoking, since it was smoking history at the time of transplantation that predicted graft failure. However, it is possible that a history of pretransplant smoking may only be associated with adverse outcomes because the patients who smoked the most pretransplant were those most likely to continue smoking posttransplant. In other words, it is possible that pretransplant smoking history was a surrogate for smoking behavior after transplan-

758 Journal of the American Society of Nephrology J Am Soc Nephrol 11: 753 759, 2000 Table 6. Cigarette smoking and cardiovascular disease a Smoked 1 to 10 pack-years at transplant 1.09 0.70 to 1.69 0.7035 Smoked 11 to 25 pack-years at transplant 1.56 1.06 to 2.31 0.0244 Smoked 25 pack-years at transplant 2.14 1.49 to 3.08 0.0001 Age 30 yr at transplant 0.46 0.27 to 0.79 0.0046 Age 45 to 60 yr at transplant 1.78 1.13 to 2.80 0.0127 Age 60 yr at transplant 3.35 1.99 to 5.63 0.0001 Renal disease from nephrosclerosis 2.17 1.36 to 3.46 0.0011 Renal disease from ADPKD 1.66 0.99 to 2.77 0.0526 Renal disease from type 1 diabetes mellitus 3.85 2.52 to 5.90 0.0001 Renal disease from type 2 diabetes mellitus 2.65 1.59 to 4.44 0.0002 Pre-CsA era (before 1/86) 1.98 1.42 to 2.77 0.0001 Post-Minnesota ALG era (after 8/92) 0.59 0.35 to 1.00 0.0482 Pretransplant bilateral nephrectomy 0.66 0.46 to 0.95 0.0248 Pretransplant IHD 2.07 1.35 to 3.16 0.0008 Pretransplant CVD 2.13 1.19 to 3.79 0.0104 a Cox proportional hazards model, n 1233, overall P 0.0001. ADPKD, autosomal dominant polycystic kidney disease; CVD, cerebral vascular disease. Other abbreviations as in Tables 3 and 4. Reference group (relative risk 1.00) smoked 0 pack-years, was age 31 to 45, renal disease was not caused by nephrosclerosis, ADPKD, or diabetes, was transplanted in the CsA era (1/86 to 8/92), did not have pretransplant bilateral nephrectomy, and did not have IHD or CVD pretransplant. Table 7. Cigarette smoking and the risk for invasive cancer a Smoked 1 to 10 pack-years at transplant 0.97 0.48 to 1.97 0.9262 Smoked 11 to 25 pack-years at transplant 1.07 0.53 to 2.16 0.8508 Smoked 25 pack-years at transplant 1.91 1.05 to 3.48 0.0329 Age 45 to 60 yr at transplant 2.09 1.18 to 3.68 0.0112 Age 60 yr at transplant 4.01 2.00 to 8.06 0.0001 Renal disease from type 1 diabetes mellitus 0.22 0.05 to 0.92 0.0378 Pretransplant splenectomy 2.18 1.22 to 3.92 0.0088 a Cox proportional hazards model, n 1161, overall P 0.0001. Reference group (relative risk 1.00) smoked 0 pack-years, age was 45, renal disease was not caused by type 1 diabetes, and did not have pretransplant splenectomy. tation. Unfortunately, we did not have adequate information on posttransplant smoking habits to analyze its effects on outcome, and additional studies are warranted. In examining the additive effects of covariates, patients who smoked but quit more than 5 yr before transplantation appeared to have better outcomes than patients who had never smoked. The reason for this is unclear. This effect was independent of other, major determinants of graft survival posttransplant. We might speculate that patients who were able to quit smoking were also patients who had other attributes that led to improved survival, attributes that were not taken into account in the multivariate analysis. For example, patients who were able to quit smoking may have been more adherent to medications. It is also possible that patients who were able to quit smoking adopted other lifestyles and habits that improved their survival after transplantation. In any case, this result should be interpreted with caution, given the relatively small number of end points for the relatively large number of variables entered into the models. Although we looked for interactions between variables, the number of patients and end points may have been too small to allow us to detect significant interactions. Thus, the apparent benefit from having quit smoking may largely be the result of a benefit in a subpopulation of patients who were heavy smokers, even though we were unable to discern this with the statistical models. It is encouraging that the reduced graft and patient survival associated with heavy smoking seemed to be abrogated by quitting more than 5 yr before transplantation. The 5-yr interval was arbitrary. However, other studies in nontransplant populations have also found that the effects of smoking on mortality dissipate over a number of years after having quit (4 7). There was no discernible effect of smoking on the rate of return to dialysis. In addition, smoking had no effect on serum creatinine during the first posttransplant year. Thus, there was no evidence from this study that smoking affected graft func-

J Am Soc Nephrol 11: 753 759, 2000 Cigarette Smoking in Renal Transplant Recipients 759 tion after renal transplantation. However, these results do not eliminate the possibility that smoking may have an effect on posttransplant renal function detectable by better measures or renal function and/or longer follow-up. Indeed, studies in nontransplant populations have shown that smoking has an adverse effect on renal function (8,9). A longer follow-up or a greater number of patients may be required to detect an adverse effect of smoking on graft function. Few studies have examined the effects of smoking in organ transplant recipients. In one investigation, the effects of smoking in 84 heart transplant recipients were examined (10). Despite the small sample size, smoking was associated with decreased patient survival and an increased rate of cancer. In another study of 210 cardiac transplant recipients, smoking correlated significantly with the occurrence of posttransplant coronary artery disease (11). Data from these retrospective, observational studies can never prove cause-and-effect relationships. However, it is difficult if not impossible to conduct randomized, controlled intervention trials to establish that quitting smoking will improve survival after organ transplantation. There is a growing shortage of organs that are suitable for transplantation, and waiting times for cadaveric transplants continue to increase. It can be argued that we (society) should attempt to maximize the potential improvement in patient survival that may result from each organ that is transplanted. In particular, we should attempt to maximize the overall benefit from cadaveric organs by reducing modifiable risk factors that negatively affect graft survival. Smoking may be such a risk factor. Evidence suggests that when appropriate interventions are used, many patients can quit smoking (12,13). Thus, every effort should be made to encourage transplant candidates to quit smoking. Indeed, it may even be in the public interest to deny renal transplantation to patients who do not make a serious attempt to quit smoking. The interests of both the individual and society may be best served by such an approach. References 1. Bartecchi CE, MacKenzie TD, Schrier RW: The human costs of tobacco use (1). N Engl J Med 330: 907 912, 1994 2. MacKenzie TD, Bartecchi CE, Schrier RW: The human costs of tobacco use (2). N Engl J Med 330: 975 980, 1994 3. Orth SR, Ritz E, Schrier RW: The renal risks of smoking. Kidney Int 51: 1669 1677, 1997 4. Hermanson B, Omenn GS, Kronmal RA, Gersh BJ: Beneficial six-year outcome of smoking cessation in older men and women with coronary artery disease: Results from the CASS registry. N Engl J Med 319: 1365 1369, 1988 5. Kawachi I, Colditz GA, Stampfer MJ: Smoking cessation and time course of decreased risks of coronary heart disease in middle-aged women. Arch Intern Med 154: 169 175, 1994 6. Friedman GD, Petitti DB, Bawol RD, Siegelaub AB: Mortality in cigarette smokers and quitters: Effect of base-line differences. N Engl J Med 304: 1407 1410, 1981 7. Ockene JK, Kuller LH, Svendsen KH, Meilahn E: The relationship of smoking cessation to coronary heart disease and lung cancer in the Multiple Risk Factor Intervention Trial (MRFIT). Am J Public Health 80: 954 958, 1990 8. Gambaro G, Verlato F, Budakovic A: Renal impairment in chronic cigarette smokers. J Am Soc Nephrol 9: 562 567, 1998 9. Ritz E, Benck U, Franek E, Keller C, Seyfarth M, Clorius J: Effects of smoking on renal hemodynamics in healthy volunteers and in patients with glomerular disease. J Am Soc Nephrol 9: 1798 1804, 1998 10. Nagele H, Kalmar P, Rodiger W, Stubbe HM: Smoking after heart transplantation: An underestimated hazard? Eur J Cardiothorac Surg 12: 70 74, 1997 11. Radovancevic B, Poindexter S, Birovljev S: Risk factors for development of accelerated coronary artery disease in cardiac transplant recipients. Eur J Cardiothorac Surg 4: 309 312, 1990 12. Silagy C, Mant D, Fowler G, Lodge M: Meta-analysis on efficacy of nicotine replacement therapies in smoking cessation. Lancet 343: 139 142, 1994 13. Hughes JR, Goldstein MG, Hurt RD, Shiffman S: Recent advances in the pharmacotherapy of smoking. JAMA 281: 72 76, 1999 14. Centers for Disease Control and Prevention: Surveillance for selected tobacco-use behaviors United States, 1990 1994. In: Surveillance Summaries, November 18, 1994. Morb Mortal Wkly Rep 43: 8, 1994