Low Cloud Cover-Adjusted Ultraviolet B Irradiance Is Associated with High Incidence Rates of Leukemia: Study of 172 Countries

Abstract

There are 52,380 cases of leukemia and 24,090 deaths from it in the US annually. Its causes are unknown and no preventive strategies have been implemented. We hypothesized that leukemia is due mainly to vitamin D deficiency, which is due mainly to low solar ultraviolet B (UVB) irradiance. To test this hypothesis, we estimated age-standardized cloud-cover-adjusted winter UVB irradiance using cloud cover data from the International Satellite Cloud Climatology Project, latitudes of population centroids, and standard astronomical calculations. Incidence rates for 172 countries, available from the International Agency for Cancer Research, were plotted according to cloud-adjusted UVB irradiance. We used multiple regression to account for national differences in elevation and average life expectancy. Leukemia incidence rates were inversely associated with cloud-adjusted UVB irradiance in males (p ≤ 0.01) and females (p ≤ 0.01) in both hemispheres. There were few departures from the trend line, which was parabolic when plotted with the equator at the center of the display, northern hemisphere countries on the right side and southern hemisphere countries on the left. The bivariate association displayed by the polynomial trend line indicated that populations at higher latitudes had at least two times the risk of leukemia compared to equatorial populations. The association persisted in males (p ≤ 0.05) and females (p ≤ 0.01) after controlling for elevation and life expectancy. Incidence rates of leukemia were inversely associated with solar UVB irradiance. It is plausible that the association is due to vitamin D deficiency. This would be consistent with laboratory studies and a previous epidemiological study. Consideration should be given to prudent use of vitamin D for prevention of leukemia.

Effect of serum vitamin D deficiency in the prevalence of haematological malignancies

“…Studies on vitamin D deficiency and geographic location have shown significant risk association in cancer prevalence and mortality. 1,2 Several reports suggested that vitamin D deficiency leads to an increased incidence and poor outcome in colorectal, breast, lung, melanoma and prostate cancers. 7 Despite the growing evidence of the relationship between vitamin D levels and solid tumour, far less is known about the risk and clinical outcomes in haematologic malignancies.…”

“…A follow-up study by the Harvard Health professionals discovered that a 25 nmol/L increase in modeled 25-hydroxy vitamin D, was associated with a 66% decrease in risk of leukaemia. 2 The high deficiency rates of vitamin D observed in the Indian subcontinent despite being a tropical country could be due to the changing lifestyles restricting to indoors, dress style and lack of awareness of the deficiency and the associated risk due to deficiency.…”

“…Vitamin D indirectly may suppress the tumour growth and progression by facilitating the immunocytotoxic killing of tumour cells by reducing the levels of immunosuppressive CD34 lymphocytes, which generally confine the cytotoxic activity of infiltrating tumour-specific CD8+T lymphocytes. 2,9,12,13 Haematological malignancies are a group of neoplasms that arise through malignant transformation of bone marrow derived cells. Leukaemia, lymphoma and myeloma are the different haematological malignancies that originate in the bone marrow or lymphatic tissues as a result of genetic injury.…”

“…14 Several population-based cohort studies have shown a linear association between lower serum vitamin D concentrations and an increased risk of overall mortality in leukaemia and the lymphoma subsets. 2,9,15,16 However, additional prospective studies are required to investigate the association between serum vitamin D concentrations and overall incidence and prognosis in all malignancies. Though India is a tropical country with plenty of sunshine, Indians are found to be vitamin D deficient and there is lack of awareness regarding the deficiency and related health effects.…”

Improving vitamin D testing and supplementation in children with newly diagnosed cancer: A quality improvement initiative at Rady Children's Hospital San Diego

“…Large ecological studies have suggested a link between vitamin D deficiency and low type B ultraviolet (UVB) irradiation with increased cancer incidence and mortality 3,4 . These studies highlight a broader role for vitamin D in the human body than previously believed, with effects on immune function, metabolism, 5,6 and cancer pathophysiology 7,8 …”