No abstract

The Norwegian counties can conveniently be divided in three groups with different annual UV exposures and different incidence rates of squamous cell carcinoma (SCC) of the skin. In view of the hypothesis that latitude and season of diagnosis may play a role for breast cancer progression, the prognosis of breast cancer as determined for summer and winter diagnosis, were evaluated in the three residential regions. Two age groups were analysed separately (stratification at 50 years). For all regions, and for all ages, the prognosis was best for women diagnosed in the summer season (Relative risk (RR) of death was 15-25% lower for summer diagnosis versus winter diagnosis). There was no significant seasonal variation of the number of new cases. For women diagnosed before the age of 50, a geographical gradient in cancer prognosis was also found (RR of death 0.6, 95% CI: 0.5-0.7 for cases diagnosed in southeast Norway and RR of death 0.8, 95% CI: 0.6-1.1 for diagnosis in the north of Norway). This is in agreement with a 1.5 times larger annual UV exposures and 3-4 times larger incidence rates of SCC in the southeast region when compared with the north region. For women diagnosed after the age of 50, no significant difference was found between the three regions. Despite a 17% higher vitamin D intake from food in north of Norway no difference in cancer survival was found for diagnosis during winter (when no significant differences in the levels of UV exposure can be detected between regions). The overall data support our earlier hypothesis that season of diagnosis and therapy start improves the survival for breast cancer.

In temperate latitudes even pandemic influenzas often show a clear seasonality. The data support the hypothesis that high fluences of UVB radiation (vitamin D level), as occur in the summer, act in a protective manner with respect to influenza.

The 2 objectives of this work were: (1) To determine whether repeated exposures to small doses from a commercial sun bed (Wolff Solarium Super Plus 100 W) over 5 weeks gave less vitamin D than repeated exposures to twice as large, but still nonerythemogenic, doses. (2) To investigate whether the contribution to the vitamin D status from such sessions of exposures was dependent on the baseline status before the start of the sessions. (3) To determine the decay rate of the induced increment of vitamin D. The sun bed sessions raised the 25-hydroxyvitamin D levels from typical winter values to typical summer values the mean value after exposure being 80 nM (±14) and the increase being 15 nM on average. Persons with the lowest initial levels got the largest increase. The level in this group was back to the pre-exposure level after 2-4 weeks. To maintain a summer level through the winter, when no vitamin D is produced by the sun in northern countries, one should consider increasing the recommended intake of vitamin D intake significantly, or encouraging the population to get moderate, nonerythemal sun bed exposures.