# Logistic Regression - Adding interactions makes Independent variable statistically insignificant

My name is Abhi & I am trying to better understand logistic regression by solving a few practice problem. I am using R and RStudio as the development environment

Problem Statement
Given the age, sex and class(first,second,third) for each passenger can you predict if he survived or died when the titanic sank

Attempt1
Simple Logistic Regression. Use age,sex and passenger class directly. The formula (in R) Survived~Pclass+Sex+Age

This gives fairly decent results - accuracy of 79% and all of independent variables are statistically significant

Attempt2
Add interactions between age,sex and passenger class. Accuracy has improved to 80% but age is no longer significant. Also none of the new terms(age-sex,age-class,sex-class,age-sex-class) are statistically significant. The formula (in R) Survived~Pclass*Sex*Age

Can some one explain why this is happening? I can accept that the new terms may not be significant but why is age no longer significant?

Any help would be much appreciated