In the Letter to the Editor by Grant [1], the author suggested geographical differences in APOE genotype distribution as an alternative hypothesis to explain the inverse correlation between incident solar radiation and coronary heart disease (CHD) mortality rates in Western Europe. However, we have some concern about this hypothesis. Based on epidemiological investigations, geographical differences have been proposed in APOE aliele distribution in healthy population; the prevalence of the APOE4 aliele increases with latitude [2, 3]. As hypothesized by the author, fresh fruits and vegetables at higher latitudes are less readily available than at lower latitudes [4]; apoE4 protein can cause the liver to produce more cholesterol and the pancreas more insulin in order to store more food as fat; as a consequence, prevalence of the APOE4 aliele increases with latitude. In light of this statement, the APOE4 aliele seems to be an mutant of APOE 2 or 3 aliele, whereas this is not evidenced by evolutionary analysis, which implies APOE4 aliele as the ancestral aliele of APOE [5, 6]. Moreover, association does not necessarily mean causation, a vexing problem often raised and debated by epidemiologists [7]. In a recent review by Prakash et al. [8], the authors suggested a relation between prevalence of headache and the latitude. Similarly, although the profile of headache matches with seasonal variations and geographical distribution of serum vitamin D levels, we believe it far-fetched to propose such a correlation. According to our current knowledge, we can only ascribe this to coincidence