Contact information Does daily tobacco smoking affect outcomes after microdecompression for degenerative central lumbar spinal stenosis? - A multicenter observational registry-based study Charalampis Giannadakis MD1,2, Sasha Gulati MD PhD1,2, Trond Nordseth MD PhD3, Ulf S. Nerland MD1,2, Michel Gulati MD4, Clemens Weber MD2,5, Øystein P. Nygaard MD PhD1,2, Tore K. Solberg MD PhD6,7, Ole Solheim MD PhD1,2, Asgeir S. Jakola MD PhD1,8 Charalampis Giannadakis MD Department of Neurosurgery, St. Olavs University Hospital, Trondheim, NO-7009, Trondheim, Norway E-mail: charalampis.giannadakis@ntnu.no RESULTS INTRODUCTION Figure 1. Study enrollment and follow-up. Table 1. Demographic characteristics, coexisting illnesses, and measures of health status for both groups (n=885). A total of 825 patients were included (619 nonsmokers and 206 smokers). For the whole patient population there was a significant difference between preoperative ODI and ODI at 1 year (17.3 points, 95 % CI 15.93–18.67, p<0.001). There was a significant difference in ODI change at 1 year between nonsmokers and smokers (4.2 points, 95 % CI 0.98–7.34, p= 0.010). At 1 year 69.6 % of nonsmokers had achieved a minimal clinically important difference (≥10 points ODI improvement) compared to 60.8 % of smokers (p=0.008). There was no difference between nonsmokers and smokers in the overall complication rate (11.6 % vs. 9.2 %, p=0.34). There was no difference between nonsmokers and smokers in length of hospital stays for either single-level (2.3 vs. 2.2 days, p=0.99) or two-level (3.1 vs. 2.3 days, p=0.175) microdecompression. Smoking was identified as a negative predictor for ODI change in a multiple regression analysis (p=0.001). . There are limited scientific data on the impact of smoking on patient-reported outcomes following minimally invasive spine surgery. Variable Non-smokers (n=619) Smokers (n=206) P-value Age – yr 67.64 62.90 <0.001 Attended college – no. (%) 193 (31.2) 39 (18.9) 0.001 Body Mass Index 27.55 26.57 0.014 Deformity (spondylolisthesis and/or scoliosis) 77 (12.4) 23 (11.2) 0.627 Previous lumbar spine surgery 115 (18.8) 32 (15.8) 0.349 ASA grade >2 120 (19.8) 50 (25.4) 0.098 Preoperative ODI 38.99 42.27 0.005 AIM The aim of this multicenter observational study was to examine the relationship between daily smoking and patient-reported outcome at 1 year using the Oswestry Disability Index (ODI) after microdecompression for single- and two-level central lumbar spinal stenosis (LSS). Secondary outcomes were the length of hospital stays, perioperative and postoperative complications. Table 2. Surgical treatments, complications, and events. Table 3. Multiple regression analysis. Difference in ODI 12 months after surgery. Variable Non-smokers (n=546) Smokers (n=279) P-value Levels decompressed – no. (%)   - Single 402 (64.9) 217 (35.1) 0.192 - Two 144 (69.9) 62 (30.1) Operation time (minutes) - Single-level decompression 83.81 84.50 0.903 - Two-level decompression 118.65 108.18 0.090 Days in hospital no. 2.32 2.23 0.992 3.09 2.27 0.175 Any complication no. (%) 72 (11.6) 19 (9.2) 0.339 Perioperative complications no. (%) 24 (3.9) 7 (3.4) 0.754 - Dural tear or spinal fluid leak 21 (3.4) 6 (2.9) 0.737 - Blood replacement or postoperative hematoma 2 (0.3) 1 (0.5) - Cardiovascular complications 1 (0.2) 0 (0) 0.564 - Anaphylactic reaction - Wrong level surgery Complications within 3 months no. (%) 50 (8.1) 12 (5.8) 0.288 - Wound infection 20 (3.2) 8 (3.9) 0.654 - Urinary tract infection - Pneumonia 4 (0.6) 2 (1.0) 0.635 - Pulmonary embolism MATERIALS & METHODS Variable Parameter estimate 95% Confidence Interval P-value +Oswestry score 21-40, pre- surgery 10.5 5.92 - 15.05 <0.0001 +Oswestry score 41-60, pre- surgery 16.5 11.67 - 21.25 +Oswestry score > 60, pre-surgery 33.1 - 39.41 Smoker –5.3 –8.40 - –2.10 0.001 Age (per 10 year) –0.9 –2.39 - 0.59 0.237 Female sex 2.3 –0.37 - 4.99 0.091 Attended college 3.0 0.02 - 6.00 0.048 Previous lumbar spine surgery –8.3 –11.72 - –4.89 *Body Mass Index 25 – 29.9 kg/m2 –0.6 –3.73 - 2.49 0.697 *Body Mass Index 30 – 34.9 kg/m2 –4.6 –8.67 - –0.62 0.024 *Body Mass Index >= 35 kg/m2 –13.2 –19.98 - –6.40 <0.001 Data were collected through the Norwegian Registry for Spine Surgery (NORspine). SUMMARY / CONCLUSION AUTHOR AFFILIATIONS Nonsmokers experienced a significantly larger improvement at 1 year following microdecompression for LSS compared to smokers. Smokers were less likely to achieve a minimal clinically important difference. However, it should be emphasized that considerable improvement also was found among smokers. Dept. of Neurosurgery, St. Olavs University Hospital, Trondheim, Norway Dept. of Neuroscience, Norwegian University of Science and Technology, Trondheim, Norway Dept. of Anesthesia, St. Olavs University Hospital, Trondheim, Norway Dept. of General Surgery, Ålesund University Hospital, Ålesund, Norway Dept. of Neurosurgery, Stavanger University Hospital, Stavanger, Norway Norwegian Registry for Spine Surgery, University Hospital of Northern Norway, Tromsø, Norway Dept. of Neurosurgery, University Hospital of Northern Norway, Tromsø, Norway Dept. of Neurosurgery, Sahlgrenska University Hospital, Gothenburg, Sweden ACKNOWLEDGEMENTS The authors would like to thank the Norwegian Registry for Spine Surgery (NORspine). The NORspine registry receives funding from the University of Northern Norway and Norwegian health authorities.