To factors which can cause an increase and explain them life expectancy​

Evidence-based studies indicate that longevity is based on two major factors, genetics and lifestyle choices.

Twin studies have estimated that approximately 20-30% of an individual's lifespan is related to genetics, the rest is due to individual behaviors and environmental factors which can be modified.

Don't smoke, don't binge drink, eat a healthy diet and take regular exercise. This can add 10 years to your life.
Maintain and develop strong social networks, with family or friends. Some studies suggest this has a protective effect on health.
Take advantage of any educational opportunities available in your adult life, even if you didn't do well at school. This seems to have health benefits.
Volunteer - There are likely to be opportunities to volunteer wherever you live and some studies suggest this can help maintain mental health and improve life expectancy.

Both the han and the roman empire decline as a result of social unrest during their collapse.