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Re: Debate is over - mistatements of fact



I thought these rather recent abstracts may be of interest since two of them 

show interesting inverse associations.  To assess the validity of the findings 

of these ecologic studies, case-control studies or cohort studies would be 

required.



Cancer. 2002 Mar 15;94(6):1867-75.    

  

An estimate of premature cancer mortality in the U.S. due to inadequate doses 

of solar ultraviolet-B radiation.



Grant WB.



wbgrant@infi.net



BACKGROUND: There are large geographic gradients in mortality rates for a 

number of cancers in the U.S. (e.g., rates are approximately twice as high in 

the northeast compared with the southwest). Risk factors such as diet fail to 

explain this variation. Previous studies have demonstrated that the geographic 

distributions for five types of cancer are related inversely to solar 

radiation. The purpose of the current study was to determine how many types of 

cancer are affected by solar radiation and how many premature deaths from 

cancer occur due to insufficient ultraviolet (UV)-B radiation. METHODS: UV-B 

data for July 1992 and cancer mortality rates in the U.S. for between 1970-

1994 were analyzed in an ecologic study. RESULTS: The findings of the current 

study confirm previous results that solar UV-B radiation is associated with 

reduced risk of cancer of the breast, colon, ovary, and prostate as well as 

non-Hodgkin lymphoma. Eight additional malignancies were found to exhibit an 

inverse correlation between mortality rates and UV-B radiation: bladder, 

esophageal, kidney, lung, pancreatic, rectal, stomach, and corpus uteri. The 

annual number of premature deaths from cancer due to lower UV-B exposures was 

21,700 (95% confidence interval [95% CI], 20,400-23,400) for white Americans, 

1400 (95% CI, 1100-1600) for black Americans, and 500 (95% CI, 400-600) for 

Asian Americans and other minorities. CONCLUSIONS: The results of the current 

study demonstrate that much of the geographic variation in cancer mortality 

rates in the U.S. can be attributed to variations in solar UV-B radiation 

exposure. Thus, many lives could be extended through increased careful 

exposure to solar UV-B radiation and more safely, vitamin D3 supplementation, 

especially in nonsummer months. Copyright 2002 American Cancer Society.



------------------

J Environ Pathol Toxicol Oncol. 2002;21(3):205-12.  



Cancer incidence rates and environmental factors: an ecological study.



Steiner GG.



ggsteiner@yahoo.com



The environmental factors latitude, temperature, and water consumption have 

been correlatedwithcancerincidencerates.To date, there is noconsensus of 

opinion that explains how these environmental factors alter the incidence of 

cancer. A fluoride belt stretches across the north and east of Africa, through 

the Middle East, across Pakistan and India, into Southeast Asia, and the south 

of China. There appears to be an association between areas with low cancer 

incidence rates and high fluoride concentrations in the water supply. This 

ecologic study attempts to determine if fluoride is correlated with cancer 

incidence rates. If so, this study also attempts to determine whether fluoride 

is a factor in the correlation between latitude, temperature, and cancer 

incidence rates. Population groups with very high cancer incidence rates and 

population groups with very low cancer incidence rates are compared to 

identify environmental factors that might explain the correlation between 

cancer incidence rates and the environmental factors of latitude, temperature, 

and fluoride.There is a positive correlation between cancer incidence rates 

and latitude (r = 0.71).There is an inverse correlation between cancer 

incidence rates and temperature (r = -0.87).There is also an inverse 

correlation between cancer incidence rates and fluoride concentration in the 

drinking water (r = -0.75). Very low cancer incidence was found in areas with 

high fluoride concentrations in the drinking water.



-------------------



Int J Epidemiol. 2001 Dec;30(6):1343-50.    



  

Ecologic versus individual-level sources of bias in ecologic estimates of 

contextual health effects.



Greenland S.



Department of Epidemiology, UCLA School of Public Health, and Department of 

Statistics, UCLA College of Letters and Science, 22333 Swenson Drive, Topanga, 

CA 90290, USA.



A number of authors have attempted to defend ecologic (aggregate) studies by 

claiming that the goal of those studies is estimation of ecologic (contextual 

or group-level) effects rather than individual-level effects. Critics of these 

attempts point out that ecologic effect estimates are inevitably used as 

estimates of individual effects, despite disclaimers. A more subtle problem is 

that ecologic variation in the distribution of individual effects can bias 

ecologic estimates of contextual effects. The conditions leading to this bias 

are plausible and perhaps even common in studies of ecosocial factors and 

health outcomes because social context is not randomized across typical 

analysis units (administrative regions). By definition, ecologic data contain 

only marginal observations on the joint distribution of individually defined 

confounders and outcomes, and so identify neither contextual nor individual-

level effects. While ecologic studies can still be useful given appropriate 

caveats, their problems are better addressed by multilevel study designs, 

which obtain and use individual as well as group-level data. Nonetheless, such 

studies often share certain special problems with ecologic studies, including 

problems due to inappropriate aggregation and problems due to temporal changes 

in covariate distributions.

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