Comprehensive Analysis: Sun Exposure and Cancer Epidemiology Study

This assignment delves into the epidemiological relationship between sun exposure and cancer risk, exploring both positive associations with skin cancers and negative associations with cancers such as breast, colon, and prostate due to vitamin D synthesis. It addresses the mechanisms by which UV radiation affects DNA and immune function, as well as adaptive responses to chronic sun exposure. The assignment analyzes the influence of factors like time of day, season, latitude, and altitude on UV radiation levels and discusses potential biases in studies, such as varying melanin concentrations and kidney/liver impairments. It proposes methods for data analysis, including risk ratio and attributable risk calculations, to determine optimal sun exposure levels. The study focuses on premenopausal women due to the high prevalence of breast cancer, aiming to provide recommendations for reducing breast cancer prevalence through informed sun exposure practices. References to relevant research articles are included to support the analysis.

Cancer Epidemiology.
Q1.
There is positive association between sun exposure and cancer of the skin. It affects exposed
parts such as legs, hand and scalp. Immediate exposure may cause sunburns which in most cases
proceed to melanoma. Long time exposure leads to basal cell and squamous cell cancers.
There is a negative association between sun exposure and cancers of the pancreas, breast, colon,
ovarian and prostatic. There is a lower risk of cancer due to increased synthesis of vitamin D
which protective against cancer.
Q2.
An adult human being can absorb about 3.65 millisiverts per year. In addition to the background
radiation, the amount of UV radiation adds up to this. The higher maximum is 4 millisieverts.
Q3.
UV radiation has ionizing effects on the DNA. This results in dimerization of base pairs which
precipitates spontaneous mutations. This is a precursor of mutations which lead to uncontrolled
cell growth leading to cancer.
It may also cause immune suppression in the body. The mechanism of the body to suppress
tumors is decreased leading to their unrestricted development.

Q4.
Chronic exposure to sun may lead to photo adaptation where there will be an increased melanin
formation which reduces the risk of cancer.
Exposure to UVB increase the production of vitamin D which is subsequently metabolized into
its active form through the liver and kidney. It enhances DNA repair which is implicated with
causing mutations.
Q5.
Breast cancer
According to Engel et al. (2010), there was a 27% reduced breast cancer incidence among
women with the highest levels of 25 (OH) vitamin D, that is, greater than 25ng/mL compared to
those with lowest levels of 19.8ng/ml. this shows the negative association with the amount of
25(OH) Vitamin D levels. Mohr et al. (2014) supports this finding through a case study on
increased survival for cancer patients attributed to vitamin D. Knight et al. (2007) established
that an increased sunlight exposure between the ages of 11 and 19 reduced the risk of breast
cancer by 35. These articles can further collaborate the finding. More studies should be done on
women in different geographical location to identify how the amount of UV influences this
protective mechanism.
Q6.
The amount of UV depends on factors such as: time of the day, season of the year, latitude,
altitude, cloud cover and reflection on surfaces. The amount of UV will vary with these
conditions. Any calculation should be made with respect the above factors. The amount of

Vitamin D levels in serum would also be used as a measure. The levels would be taken in
different days, seasons latitude and altitude and recording the amount of radiation. The radiation
dose should be associated with 25(OH) vitamin D formed.
Q7.
Biases may arise if the people in the study have different melanin concentration levels. This may
be a point of disparity as the amount of UV penetrating is varied hence the levels of serum
vitamin D may vary. The association of amount of UV light and vitamin D may not be accurate.
This can be overcome by including skin color as one of the factors in forming the cohorts.
Kidney and liver impairment may be the reason why serum concentration may be low. To offset
this, I would ensure the kidney and liver function tests are parameters for qualification for the
study. This will prevent confounding bias.
Ecological fallacy can be avoided by ensuring all research persons participate in the study and
not making inferences without research.
Q8.
Data on the level of vitamin D and the number of subjects in the study. Vitamin D level will be
an indicator of the factor introduced by UV exposure. From the data the risk ratio can be
determined. The attributive risk calculation will show the relationship between the exposure and
the outcome. A positive one will show causation while the negative will indicate prevention.

Q9.
Determining the odd ratio and calculating the attributive risk. Determine the level at which it
becomes zero and this becomes the limit. The range should between the optimum results
achieved and no effect at all. From all the ranges, the mean should be determined and the
allowable standard deviations calculated to determine the appropriate sun exposure.
Q10.
I would choose premenopausal women for the high prevalence of breast cancer among them.
breast cancer being the commonest diagnosed cancer in females, the occurrence is very likely
hence the study is more likely to be fruitful. A study in this cancer would be for the greater good.
Determining the range of radiation likely to cause a negative association. Determining the time
of the day and the season when its optimum; depending on the latitude, altitude and cloud cover.
This will provide a recommendation likely to influence breast cancer prevalence.

References.
(https://www.ncbi.nlm.nih.gov/pubmed/24075798)
Knight JA, Lesosky M, Barnett H, Raboud JM, Vieth R. Vitamin D and reduced risk of breast
cancer: a population-based case-control study. Cancer Epidemiol Bio Prev 2007; 16: 422-9;
http://dx.doi.org/10.1158/1055-9965.EPI-06-0865.
Engel P, Fagherazzi G, Boutten A, Dupre T, Mesrine S, Boutron-Rualt MC, Clavel-Chapelon
F. Serum 25(OH)D vitamin D and risk of breast cancer: A nested case-control study from the
French E3N Cohort. Cancer Epidemiol Bio Prev 2010; 19:2341-50;
http://dx.doi.org/10.1158/1055-9965.EPI-10-0264.
Mohr SB, Gorham ED, Kim J, Hofflich H, Garland CF. Meta-analysis of vitamin D sufficiency
for improving survival of patients with breast cancer. Anticancer Res 2014; 34:1163-6;
PMID:24596354