In the full version of the paper, the important work by Acheson is
referenced as the third reference.
Reply to Ross
MS is a multifactorial disease, due to space limitations; we could
not
discuss the role of other possible causal factors, including herpes
viruses.
We agree that infectious agents are also likely to be important. They may
operate independently of a possible low sun exposure effect.Alternatively,
low sun
exposure may modify host response to infection.(1)
Reply to Lily
The past sun exposure measurements we have employed are those
utilised by
skin cancer epidemiologists to establish associations between past UVR
exposure and
disease. Subjects were unaware of the hypotheses tested and were asked to
provide their opinion
on the possible role in MS causation of a large number of factors,
including factors that have never been associated with MS.
The discrepancy between Leeds and Alberta that Dr Lily mentions
shows the potential problems of using ecological data (2) and the need to
conduct individual level measures of sun exposure as we have done. The
relationship between skin type and immunology is not yet well understood
and it is hoped that the our finding of an association between fairer skin
and MS will contribute to that issue.
Our study reported beneficial effects for more than one hour of sun
exposure
a day during winter weekends at a latitude of 43o S. Although the risks
of
excessive sun exposure may outweigh the benefits, this may not be the case
for moderate rather than excessive sun exposure, particularly during
winter.
Reply to Merckx
Thank you for your suggestion of this interesting concept.
1 McMichael AJ, Hall AJ. Multiple sclerosis and ultraviolet
radiation: time to shed more light.
Neuroepidemiology. 2001 Aug;20(3):165-7.
2 Piantadosi S, Byar DP, Green SB. The ecological fallacy.
Am J Epidemiol. 1988 May;127(5):893-904.
Rapid Response:
Authors' reply
Reply to Acheson
In the full version of the paper, the important work by Acheson is
referenced as the third reference.
Reply to Ross
MS is a multifactorial disease, due to space limitations; we could
not
discuss the role of other possible causal factors, including herpes
viruses.
We agree that infectious agents are also likely to be important. They may
operate independently of a possible low sun exposure effect.Alternatively,
low sun
exposure may modify host response to infection.(1)
Reply to Lily
The past sun exposure measurements we have employed are those
utilised by
skin cancer epidemiologists to establish associations between past UVR
exposure and
disease. Subjects were unaware of the hypotheses tested and were asked to
provide their opinion
on the possible role in MS causation of a large number of factors,
including factors that have never been associated with MS.
The discrepancy between Leeds and Alberta that Dr Lily mentions
shows the potential problems of using ecological data (2) and the need to
conduct individual level measures of sun exposure as we have done. The
relationship between skin type and immunology is not yet well understood
and it is hoped that the our finding of an association between fairer skin
and MS will contribute to that issue.
Our study reported beneficial effects for more than one hour of sun
exposure
a day during winter weekends at a latitude of 43o S. Although the risks
of
excessive sun exposure may outweigh the benefits, this may not be the case
for moderate rather than excessive sun exposure, particularly during
winter.
Reply to Merckx
Thank you for your suggestion of this interesting concept.
1 McMichael AJ, Hall AJ. Multiple sclerosis and ultraviolet
radiation: time to shed more light.
Neuroepidemiology. 2001 Aug;20(3):165-7.
2 Piantadosi S, Byar DP, Green SB. The ecological fallacy.
Am J Epidemiol. 1988 May;127(5):893-904.
Competing interests:
Authors of original article
Competing interests: No competing interests