Higher education linked to higher brain tumour risk

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Higher education and socio-economic status consistently linked to a heightened risk of developing a brain tumour, found a large University College London observational study of more than 4m Swedes.

Gliomas, in particular, were more common among people who had studied at university for at least three years than they were among those who didn’t go on to higher education, the data show.

The researchers, led by Amal R Khanolkar at the University College London, base their findings on more than 4.3m Swedes, all of whom were born between 1911 and 1961 and living in Sweden in 1991. They were monitored between 1993 and 2010 to see if they developed a primary brain tumour, and information on educational attainment, disposable income, marital status, and occupation was obtained from national insurance, labour market and national census data.

During the monitoring period, 1.1m people died and more than 48,000 emigrated, but 5,735 of the men and 7,101 of the women developed a brain tumour.

Men with university level education, lasting at least three years, were 19% more likely to develop a glioma – a type of cancerous tumour arising in glial cells that surround and support neurons in the brain – than men whose educational attainment didn’t extend beyond the period of compulsory schooling (9 years).

Among women, the magnitude of risk was 23% higher for glioma, and 16% higher for meningioma – a type of mostly non-cancerous brain tumour arising in the layers of tissue (meninges) that surround and protect the brain and spinal cord – than it was for women who didn’t go on to higher education.

Taking account of potentially influential factors, such as marital status and disposable income, only marginally affected the size of the risk, and only among the men. High levels of disposable income were associated with a 14% heightened risk of glioma among men, but had no bearing on the risk of either meningioma or acoustic neuroma – a type of non-cancerous brain tumour that grows on the nerve used for hearing and balance. Nor was disposable income associated with heightened risk of any type of brain tumour among the women.

Occupation also seemed to influence risk for men and women. Compared with men in manual roles, professional and managerial roles (intermediate and high non-manual jobs) were associated with a 20% heightened risk of glioma and a 50% heightened risk of acoustic neuroma.

The risk of glioma was also 26% higher among women in professional and managerial roles than it was for women in manual roles, while the risk of meningioma was 14% higher. Single men also seemed to have a significantly lower risk of glioma than married/co-habiting men, but, on the other hand, they had a higher risk of meningioma. No such associations were evident among the women.

This is an observational study so no firm conclusions can be drawn about cause and effect, and the researchers point out that they were not able to glean information on potentially influential lifestyle factors. But they emphasise that their findings were consistent, and they point to the strengths of using population data.

Abstract
Background: The aim was to investigate associations between different measures of socioeconomic position (SEP) and incidence of brain tumours (glioma, meningioma and acoustic neuroma) in a nationwide population-based cohort.
Methods: We included 4 305 265 individuals born in Sweden during 1911–1961, and residing in Sweden in 1991. Cohort members were followed from 1993 to 2010 for a first primary diagnosis of brain tumour identified from the National Cancer Register. Poisson regression was used to compute incidence rate ratios (IRR) by highest education achieved, family income, occupational group and marital status, with adjustment for age, healthcare region of residence, and time period.
Results: We identified 5735 brain tumours among men and 7101 among women during the study period. Highly educated men (≥3 years university education) had increased risk of glioma (IRR 1.22, 95% CI 1.08 to 1.37) compared to men with primary education. High income was associated with higher incidence of glioma in men (1.14, 1.01 to 1.27). Women with ≥3 years university education had increased risk of glioma (1.23, 1.08 to 1.40) and meningioma (1.16, 1.04 to 1.29) compared to those with primary education. Men and women in intermediate and higher non-manual occupations had increased risk of glioma compared to low manual groups. Compared to those married/cohabiting, being single or previously married/cohabiting was associated with decreased risk of glioma in men. Men in non-manual occupations had ∼50% increased risk of acoustic neuroma compared to men in low manual occupations.
Conclusions: We observed consistent associations between higher SEP and higher risk of glioma. Completeness of cancer registration and detection bias are potential explanations for the findings.

Authors
Amal R Khanolkar, Rickard Ljung, Mats Talbäck, Hannah L Brooke, Sofia Carlsson, Tiit Mathiesen, Maria Feychting

BMJ material
Journal of Epidemiology & Community Health abstract


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