[2 methods for the study of differential mortality based on sex: rates ratio and orthogonal regression].

Sex mortality differential is studied for all the causes of death, in La Coruña (Galicia, Spain), according to geographic area, zone (urban, semiurban and countryside) and decade (1961-1970 y 1971-1980). Two study methods are compared: a) Rate ratio (with direct age-adjusted rates); and b): Differential (Dj) between observed rate (M) and expected rate (M), for male mortality, according to female level (orthogonal regression model). t-Student-Fisher tests have been used to compare an observed mean and a theoretic one, and to compare two observed means, with independent data. An increase in male overmortality is found, from one to the other decade (112.9% to 117.0%), confirmed by orthogonal method: respectively 5.38 deaths every 100,000 and 16.81 deaths. This over-mortality is more frequent in the urban areas, while inframortality appears mainly in countryside areas. Furthermore, male overmortality increases in urban zones and decreases in semiurban and rural zones.