Welcome to the community!
You can surely make such an interpretation, as long as b is the regression coefficient of y on x, where x denotes age and y denotes the time spent on following politics.
(I don't know what IV and DV mean, and hence I'm using generic x and y. I'm sure you'll be able to relate it.)
On the other hand, you can't make such an interpretation based on the correlation coefficient r. The sign of r will tell you the direction of the linear relationship, and its magnitude will inform you about the magnitude (strong, moderate, week, etc.) of that relationship.