It's very easy to see how this idea came about. Those who had unhealthy, short, quick breaths did not live as long. Qigong and Tai Chi all have breathing at the core of their systems, and Taoists worked very hard to lengthen the time it took to take breaths. In reality, they are all improving the cardiovascular system, which makes a person more likely to live longer.
So let's have a go at living longer:
1. Without forcing it, slow down your breathing.
2. Stand or sit up straight, so you don't compress your chest and stomach.
3. Reduce tension around the neck and shoulders by regularly stretching and limbering.
4. Use your stomach to breathe, rather than your chest.
5. Without forcing it, make the transitions between inward and outward breaths as smooth as possible.
And be happy.