Sister chromatid exchange frequency correlates with age, sex and cigarette smoking in a 5-year material of 553 healthy adults

It is essential to take as many confounding factors as possible into consideration in the planning and evluation of studies by the SCE-test. It is still controversial whether age and sex are factors contributing to the wide intra-personal variability of SCE. Therefore, we have analyzed data on a total of 553 healthy adults in whom SCE were examined during a 5-year period. Using the transformation y=(sum SCE)1/2+(sum SCE+1)1/2 the model y=b0+b1 x Age+b2Xcig./day was studied by multiple linear regression. When the data on all females (n=358) and all males (n=195) were studied separately, the daily cigarette consumption was the most important in both groups, but age was also statistically significant. Using the weighted means of b-and s(b)-values, the regressions converted to SCE/cell were: Females: SCE/cell=8.00+0.017XAge+0.054XCig./day; Males: SCE/cell=7.51+0.017XAge+0.054XCig./day, the difference between females and males being 0.49 ± 0.10. i. e., highly statistically significant. It was concluded that: (1) There is a significant influence of each of the factors sex, age and cigarette consumption on spontaneous SCE rates. (2) However, age and cigarette consumption together explain only 17% and 19% of the inter-personal variation among females and males, respectively, (3) Therefore, attention should be directed towards identification of other factors that contribute more to this variation, and it might be worthwhile to investigate the possible influence of dietary habits.