Worldwide increasing incidences of cutaneous malignant melanoma

Abstract

The incidence of cutaneous malignant melanoma (CMM) has been increasing at a steady rate in fair-skinned populations around the world for decades. Scientists are not certain why CMM has been steadily increasing, but strong, intermittent UVB (290-320 nm) exposures, especially sunburn episodes, probably initiate, CMM, while UVA (321-400 nm) passing through glass windows in offices and cars probably promotes it. The CMM incidence may be increasing at an exponential rate around the world, but it definitely decreases with increasing latitude up to ~50°N where it reverses and increases with the increasing latitude. The inversion in the incidence of CMM may occur because there is more UVA relative to UVB for most of the year at higher latitudes. If windows, allowing UVA to enter our indoor-working environment and cars, are at least partly responsible for the increasing incidence of CMM, then UV filters can be applied to reduce the rate of increase worldwide.

Figure 1

Temporal exponential increase in the incidence of CMM by latitude worldwide. Note that only New Zealand (40°S) and Northern Europe (60°N) have linear rates of increase.

Figure 2

The incidence of CMM in the world's white populations for the year 2000 based on IARC data. The trend line indicates an increasing exponential incidence with decreasing latitude; however, a reversal appears to occur above ∼50°N where the incidence increases with increasing latitude. Both Northern Europe and New Zealand, where there is ozone depletion, only have linear increases in the incidence of CMM; whereas, everywhere else in the world the increasing incidence is exponential. Note that in Northern Europe only Iceland has an exponential increase in CMM.

Figure 3

(a) The data indicates an increasing incidence of CMM in the white population of the USA for six decades at three latitudes: ∼34°N (average of Los Angeles, California; Atlanta, Georgia; New Mexico), 39°N (average of San Francisco, California, and Utah) and 43°N (average of Iowa, Michigan, Connecticut, and Upstate New York). The CMM incidences at 34°N and 43°N are increasing at exponential rates while at 39°N, it is increasing at a linear rate (determined by comparing R ² values for the linear and exponential trend lines). (b) The CMM incidence data at 39°N changes from linear to exponential and the 43°N data changes from exponential to linear when Connecticut is averaged with San Francisco and Utah.

Figure 4

(a) The SEER 9 data from 1975 to 2007 indicates a linear increasing incidence in CMM (R ² is 0.9954). Five years of data was averaged to obtain each data point, for example, the data point for 1975 includes averaged data from 1973 to 1977. If the data is plotted out year by year the trend line and R ² values indicate it is a linear increase since 1973. Even if we add the IARC data for 1960, 1965, and 1970 to the SEER data, the incidence is still increasing in a linear manner from 1960 to 2005. (b) However, if one adds in the data for Connecticut and New York State extending it back 6 decades to 1940, then the increase appears to be exponential (R ² is 0.9755) rather than linear (R ² is now 0.9189).