Background: Offshore workers in the Norwegian upstream petroleum industry are exposed to a number of chemicals such as organic solvents, mineral oils and other hydrocarbons, possibly contributing to an increased risk of multiple sclerosis (MS).
Objective: To estimate the risk of MS in this population compared with the general working population in Norway, adjusting for education.
Methods: Using the Norwegian Registry of Employers and Employees we included all 27,900 offshore workers registered from 1981 to 2003 and 366,805 referents from the general working population matched by gender, age and community of residence. The cohort was linked to the Norwegian MS Registry and the Norwegian Education Registry.
Results: There was no increased risk of MS among the offshore workers. We found a marked and linear inverse relationship between level of education and the risk of MS in the total study population, with a rate ratio of 0.48 (95% CI, 0.53 to 0.88) for workers with a graduate degree compared to workers with elementary school only.
Conclusions: These findings do not support a major aetiological role of petroleum-based products, but rather point to smoking and other lifestyle factors related to the level of education as being important for the risk of MS.
AscherioAMungerKL. Environmental risk factors for multiple sclerosis. Part II: Noninfectious factors. Ann Neurol2007; 61: 504–513.
2.
AscherioAMungerKL. Environmental risk factors for multiple sclerosis. Part I: The role of infection. Ann Neurol2007; 61: 288–299.
3.
HernánMAOlekMJAscherioA. Cigarette smoking and incidence of multiple sclerosis. Am J Epidemiol2001; 154: 69–74.
4.
AscherioAMungerKLSimonKC. Vitamin D and multiple sclerosis. Lancet Neurol2010; 9: 599–612.
5.
AmaducciLArfaioliCInzitariDMarchiM. Multiple sclerosis among shoe and leather workers: an epidemiological survey in Florence. Acta Neurol Scand1982; 65: 94–103.
6.
KrebsJMParkRMBoalWL. A neurological disease cluster at a manufacturing plant. Arch Env Health1995; 50: 190–195.
7.
HenryJPWilliamsonDMSchifferRWagnerLShireJGarabedianM. Investigation of a cluster of multiple sclerosis in two elementary school cohorts. J Environ Health2007; 69: 34–38.
8.
GregoryACIIShendellDGOkosunISGiesekerKE. Multiple sclerosis disease distribution and potential impact of environmental air pollutants in Georgia. Sci Total Environ2008; 396: 42–51.
9.
SteinsvågKBråtveitMMoenBE. Exposure to carcinogens for defined job categories in Norway’s offshore petroleum industry, 1970 to 2005. Occup Environ Med2007; 64: 250–258.
10.
KirkeleitJRiiseTBråtveitMMoenBE. Increased risk of acute myelogenous leukemia and multiple myeloma in a historical cohort of upstream petroleum workers offshore. Cancer Causes Control2008; 19: 13–23.
11.
KirkeleitJRiiseTBjørgeTMoenBEBråtveitMChristianiDC. Increased risk of oesophageal adenocarcinoma among upstream petroleum workers. Occup Environ Med2010; 67: 335–340.
12.
GryttenNGladSBAarsethJHNylandHMidgardRMyhrKM. A 50-year follow-up of the incidence of multiple sclerosis in Hordaland County, Norway. Neurology2006; 66: 182–186.
LandtblomAMFlodinUSöderfeldtBWolfsonCAxelsonO. Organic solvents and multiple sclerosis: a synthesis of the current evidence. Epidemiology1996; 7: 429–433.
15.
SverdrupBKallbergHBengtssonCLundbergIPadtukovLAlfredssonL. The Epidemiological Investigation of Rheumatoid Arthritis study group. Association between occupational exposure to mineral oil and rheumatoid arthritis: results from the Swedish EIRA case-control study. Arthritis Res Ther2005; 7: R1296–R1303.
16.
KirkeleitJRiiseTBråtveitMMoenBE. Exposure to benzene on a crude oil production ship. Ann Occup Hyg2006; 50: 123–129.
17.
HuebnerWWWojcikNCJorgensenGMarcellaSPNicolichMJ. Mortality patterns and trends among 127,266 U.S.-based men in a petroleum company: update 1979-2000. J Occup Environ Med2009; 51: 1333–1348.
18.
HuebnerWWWojcikNCJorgensenGMarcellaSPNicolichMJ. Mortality patterns and trends among 49,705 U.S.-based women in a petroleum company: update 1979-2000. J Occup Environ Med2010; 52: 99–108.
19.
BarthSKKangHKBullmanTAWallinMT. Neurological mortality among US Veterans of the Persian Gulf War: 13-year follow up. Am J Ind Med2009; 52: 663–670.
20.
NeubergerJSLynchSGSuttonMLHallSBFengCSchmidtWR. Prevalence of multiple sclerosis in a residential area bordering an oil refinery. Neurology2004; 63: 1796–1802.
21.
WongORaabeGK. A critical review of cancer epidemiology in the petroleum industry, with a meta-analysis of a combined database of more than 350,000 workers. Regul Toxicol Pharmacol2000; 32: 78–98.
22.
GunRTPrattNRyanPRoderD. Update of mortality and cancer incidence in the Australian petroleum industry cohort. Occup Environ Med2006; 63: 476–481.
23.
JhaP. Social inequalities in male mortality, and in male mortality from smoking: indirect estimation from national death rates in England and Wales, Poland, and North America. Lancet2006; 368: 367–370.
24.
RiiseTNortvedtMWAscherioA. Smoking is a risk factor for multiple sclerosis. Neurology2003; 61: 1122–1124.
MungerKLChitnisTAscherioA. Body size and risk of MS in two cohorts of US women. Neurology2009; 73: 1543–1550.
27.
GiovannucciE. Epidemiology of vitamin D and colorectal cancer: causal or causal link?J Steroid Biochem Mol Biol2010; 121: 349–354.
28.
GhadirianPDadgostarBAzaniRMaisonneuveP. A case-control study of the association between sociodemographic, lifestyle and medical history factors and multiple sclerosis. Can J Public Health2001; 92: 281–285.
29.
MontgomerySMLambeMOlssonTEkbomA. Parental age, family size, and risk of multiple sclerosis. Epidemiology2004; 15: 717–723.
30.
MillerHRidleyAShapiraK. Multiple sclerosis. A note on social incidence. BMJ1960; 2: 343–345.
31.
RussellWR. Multiple sclerosis: occupational and social group at onset. Lancet1971; 2: 832–834.
