AACR: Sun Exposure May Protect Against NHL

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AACR Abstract Number: LB-228

Sun exposure may protect against non-Hodgkin lymphoma: A case-control

study

Ann Maree ,1 Bruce Armstrong,1 M. Vajdic,2 J.

,3 Grulich,2 Lin Fritschi,4 Sam Milliken,3 Kaldor,2

Geza Benke,5 Anne Kricker.1 Univ. of Sydney,1 Sydney, NSW, Australia,

National Centre for HIV Epidemiology and Clinical Research,2 Sydney,

Australia, St 's Hospital,3 Sydney, Australia, Univ. of

Western Australia,4 Perth, Australia, Monash Univ.,5 Melbourne,

Australia.

Incidence of non-Hodgkin lymphoma (NHL) has increased in parallel

with incidence of cutaneous melanoma and been observed to correlate

inversely with latitude in populations of European origin. Risk of

NHL is also increased in people with a past history of skin cancer.

These observations suggest that sun exposure may cause NHL. We tested

this hypothesis in a population-based case-control study using direct

measures of sun exposure.

Adults aged 20-74 years living in NSW and ACT, Australia, were the

study population. Registry-based cases (n=704; 85% of those eligible

and contactable) were diagnosed January 2000 to August 2001 and

notifications were fast-tracked to the study. Controls (n=694; 61% of

those eligible and contactable) were randomly selected from state

electoral rolls and frequency-matched to cases by age, sex and state

of residence. A self-administered questionnaire and a telephone

interview measured outdoor hours on working and non-working days and

vacations at 10, 20, 30, 40, 50 and 60 years of age. We have shown

that total hours recalled for decade years is highly correlated with

more detailed recall of lifetime outdoor hours over the same period.

Recall of occupational outdoor hours was also obtained in a full

occupational history. We have previously shown recall of outdoor

hours to be reliable when using these methods and their use has

demonstrated expected relationships between sun exposure and disease

in case-control studies. Multivariate logistic regression models of

NHL and sun exposure contained the three matching variables,

ethnicity and measures of sun sensitivity as covariates.

Contrary to prior expectations, risk of NHL fell consistently and

significantly with increasing total time outdoors and time outdoors

on non-working days. Relative to a value of 1.0 for the lowest

quarter of total outdoor time, the odds ratios (ORs) for successively

higher quarters were 0.72 (95% CI 0.53-0.98), 0.66 (0.48-0.91) and

0.65 (0.46-0.91) (<i>p</i>_trend=0.01). There was a much

stronger inverse association of exposure on non-working days with

NHL; the corresponding ORs were 0.83 (0.61-1.11), 0.57 (0.42-0.79)

and 0.47 (0.34-0.66) (<i>p</i>_trend=0.0001). Risk of NHL

also fell with increasing reported sun exposure during vacations with

ORs of 0.98 (0.72-1.32), 0.82 (0.60-1.12) and 0.60 (0.43-0.85)

(<i>p</i>_trend=0.003). These associations were present in

both men and women but stronger in women. The apparent protective

effect of total hours outdoors was greatest with exposure in

childhood. There was little evident trend in NHL risk with outdoor

hours on working days in the decade years or summed across all

occupations.

Our results provide strong statistical evidence that sun exposure is

inversely associated with non-Hodgkin lymphoma. Increasing evidence

that vitamin D may protect against cancers of various types makes UV

mediated synthesis of vitamin D in skin a plausible mechanism whereby

sun exposure might protect against NHL.

Presenter: Bruce Armstrong

Affiliation: Univ. of Sydney; E-mail: n/a

Copyright © 2004 American Association for Cancer Research. All rights

reserved. Citation information: Proceedings of the AACR, Volume 45,

March 2004.