Accelerated aging is a highly disputed topic as is aging in general. Technically anything you do which triggers stress could potentially create cortisol.
You should look up telomere research on resistance training versus cardiovascular workout. In a nutshell some researchers have observed a significant change in telemere length and telemerase activity with an increase of cardiovascular activity. Whereas resistance training may have a minor affect on telemerase activity with no observable effect on telomere lengths. They speculate the benefits of cardiovascular activity is likely due to an increase of blood flow with the carrying of nitric oxide.
Maybe it's my fault for not explaining it a little better. I do think strength training and cardiovascular is necessary in one's life in moderation. However if you look at the average person with a sedentary life style, while keeping obesity rate in mind, I think it's safe to say people Per capita will find a larger benefit from cardiovascular activity.