Relative mortality and survival in multiple sclerosis: findings from British Columbia, Canada
- 1Faculty of Medicine, Division of Neurology, University of British Columbia, Vancouver, British Columbia, Canada
- 2Department of Statistics, University of British Columbia, Vancouver, British Columbia, Canada
- 3Multiple Sclerosis Clinic, University of British Columbia, Vancouver, British Columbia, Canada
- Correspondence to Dr E Kingwell, Faculty of Medicine (Neurology), UBC Hospital, 2211 Wesbrook mall, University of British Columbia, Vancouver, BC V6T 2B5, Canada;
Contributors EK was responsible for designing the study, ensuring the data integrity, managing the data, statistical analysis, interpretation of the data and drafting the manuscript. MvdK contributed substantially to the statistical analyses and interpretation of the data, and drafting and editing of the manuscript. AS provided intellectual comments and editing of the manuscript. YZ contributed to the statistical analysis plan and provided intellectual comments and editing of the manuscript. FZ contributed to the statistical analyses, and to editing of the manuscript. JO provided intellectual comments and editing of the manuscript. HT obtained funding for the study, contributed substantially to the study deign and revisions of the manuscript, and served as a general advisory role. All authors read and approved the final version of the manuscript.
- Received 26 May 2011
- Revised 13 July 2011
- Accepted 16 July 2011
- Published Online First 23 August 2011
Objective To examine mortality and factors associated with survival in a population based multiple sclerosis (MS) cohort.
Methods Clinical and demographic data of MS patients registered with the British Columbia MS clinics (1980–2004) were linked to provincial death data, and patients were followed until death, emigration or study end (31 December 2007). Absolute survival and the influence of patient characteristics (sex, disease course (primary progressive (PPMS) vs relapsing onset (R-MS)) and onset age) were estimated by Kaplan–Meier analyses (from birth and disease onset). Mortality relative to the general population was examined using standardised mortality ratios. Excess mortality associated with patient characteristics and time period of cohort entry was assessed by relative survival modelling.
Results Of 6917 patients, 1025 died. Median survival age was 78.6 years (95% CI 77.5 to 79.7) for women and 74.3 years (95% CI 73.1 to 75.4) for men. Survival from onset was longer for R-MS (49.7 years; 95% CI 47.9 to 51.5) than for PPMS (32.5 years; 95% CI 29.5 to 35.7); however, survival age was similar. The overall standardised mortality ratios was 2.89 (95% CI 2.71 to 3.07), and patients survived approximately 6 years less than expected, relative to the general population. PPMS had a higher relative mortality risk compared with R-MS (relative mortality ratio (RMR) 1.52; 95% CI 1.30 to 1.80). Women with PPMS had a relative survival disadvantage compared with men with PPMS (RMR 1.55; 95% CI 1.19 to 2.01). Relative survival within 10 years of cohort entry was similar between time periods.
Conclusions Some of the longest MS survival times are reported here but the risk of death was still greater than in the age, sex and calendar year matched general population. No evidence of increased survival over time was found when improved survival in the general population was taken into consideration.
Funding This study was funded by the Canadian Institutes of Health Research (MOP-82738; PI: HT). EK is funded by a Postdoctoral Fellowship from the Multiple Sclerosis Society of Canada. AS is funded through grants from the Canadian Institute of Health Research (MOP-93646; PI: HT) and the National Multiple Sclerosis Society (RG 4202-A-2; PI: HT), and a Postdoctoral Fellowship from the Multiple Sclerosis Society of Canada. YZ receives research funding from the Canadian Institutes of Health Research, the Multiple Sclerosis Society of Canada and the National Multiple Sclerosis Society. JO receives financial support from the Christopher Foundation (Vancouver) and the University of British Columbia. HT is funded by the Multiple Sclerosis Society of Canada (Don Paty Career Development Award); is a Michael Smith Foundation for Health Research Scholar and the Canada Research Chair for Neuroepidemiology and Multiple Sclerosis. HT receives research support from CIHR, the MS Society of Canada and the US National MS Society. The BC MS database has been funded by an unrestricted grant from Dr Donald Paty and the MS/MRI Research Group. The funding agencies had no role or involvement in the study design or conduct, data collection, analysis or interpretation, manuscript preparation or the decision to submit the paper for publication.
Competing interests EK has received reimbursement of travel and accommodation costs to present at and attend conferences from the endMS Research and Training Network, the International Society for Pharmacoepidemiology and Bayer Schering Pharma. AS has received travel grants to present and attend conferences from the endMS Research and Training Network and the European Committee for Treatment and Research in Multiple Sclerosis. JO has received speaker honoraria, consulting fees, travel grants, research grants or educational grants from Aspreva, Aventis, Bayer, Biogen-Idec, BioMS, Corixa, Genentech, Novartis, Serono, Talecris and Teva-neurosciences and receives fees for services from Bayer, Novartis and Biogen Idec to serve on advisory committees. HT has received research support from the MS Society of Canada, the US National MS Society, Canadian Institutes of Health Research and UK MS Trust. She has received speaker honoraria and/or travel expenses to attend conferences from Consortium of MS Centres, US National MS Society, Swiss Multiple Sclerosis Society, the University of British Columbia MS Research Program, Bayer Pharmaceuticals (speaker; honoraria declined) and Teva Pharmaceuticals (speaker). Unless otherwise stated, HT's speaker honoraria are donated to an MS charity or to an unrestricted grant for use by her research group.
Ethics approval This study was conducted with the approval of the University of British Columbia Clinical Research Ethics Board.
Provenance and peer review Not commissioned; externally peer reviewed.