 For reasons that remain unclear, data have shown that males tend to have a longer life expectancy than females, but recent studies suggest this gender gap may no longer exist perhaps due to improvements in health care facilities, while a recent study from Ireland identified a link between the female hormone estrogen and worse outcomes in CF.The distribution of CF alleles varies among populations.The frequency of ΔF508 carriers has been estimated at one in 200 in northern Sweden, one in 143 in Lithuanians, and one in 38 in Denmark.