Walking is an excellent physical activity for aging men and women.  University of Pittsburgh School of Medicine (Pennsylvania, USA) researchers reported that older adults who boost their walking speed over time live longer. The team followed 439 adults, ages 65 and over, and found those who improved their walking speed over a one-year period were 18% less likely to die over the next eight years.  Interestingly, the study found that walking speed during the first year of study was the only factor to predict the subjects’ long-term survival; other tests of physical health, and self-assessment surveys, did not. 

Whenever possible, pick up the pace when walking. Whereas an average walking pace is close to a 15 minute mile, a good  fitness pace will vary depending on your fitness level, walking technique, walking goals, and terrain. For general fitness walking you should try to walk at a pace that increases your heart rate, and that you can maintain for 30 to 60 minutes. Use the talk test: If you can't speak without gasping for air you are walking too fast. If you are walking slow enough that you can carry a tune you are probably walking too slow. 

Consult an anti-aging physician to construct an exercise regimen that is appropriate for your medical needs.