The founding of the People's Republic of China (PRC) in 1949 brought a wave of change and development to China. But perhaps there is no better indicator of how much people's livelihoods improved than the changes in life expectancy.

In 1949 the average life expectancy was 36 years. In just seven decades that figure has more than doubled to 77 years. It is considered one of the most rapid and sustained increases in history.

Chinese are not only living longer but the country's mature citizens are thriving too. And I discovered this at the Rainbow Bay Senior Center in Shanghai. Like other nursing homes springing up across China, this modern facility cares for the social, mental and physical well-being of China's growing elderly population. From the moment we arrived, we saw elderly people engaging in various activities such as Tai-Chi, drumming, calligraphy classes and physical therapy.

It was at this busy center that we met the charming Zhang Xianxun. Between working shifts at the center's in-house supermarket, the energetic 89-year-old has even managed to publish his memoirs. All thanks to his good health –  something he doesn't take for granted. 

"I remember when my father died. He was only around 40 years old, and I was nine years old. He had lung disease, but there was no medicine, nor hospital. People lived very short lives," he told me.    

China's growth in life expectancy is seen as a key marker of the nation's development. It's a trend that Qi Nan, the deputy general manager of the nursing home, believes will continue. "The Chinese government has increased its spending on health care. People's awareness of health has improved, and they are adopting healthier lifestyles. For these reasons, more people in our country are living longer. Take our nursing home as an example. The average age is 86 and the oldest person is 103 years old." 

For Grandpa Zhang, the secret to a long and healthy life is much simpler. "I have a good attitude and I am happy," he said. 

A good attitude certainly helps. But experts like fellow octogenarian Professor Wen Yumei credit key public health interventions in the 1950s for China's rising life expectancy.

We met Professor Wen at Fudan University's Department of Microbiology, where even at the age of 85, she continues to teach, conduct research and mentor students. I am quite moved and inspired by her passion and drive, as she told me about the groundbreaking Hepatitis research that she was currently working on.

The professor told me that there were four key interventions in the 1950s that saved millions of lives. "The most important part is to control infectious diseases. After the founding of the PRC, the most prevalent diseases were infectious diseases. China developed many vaccines against that," she said. 

Improvements in maternal and infant care also accounted for a significant improvement in life expectancy. Professor Wen said the fact that many babies were dying brought down the overall average of life expectancy. Other contributing factors include better water supplies and education.

Night falls across Shanghai, but for one group of old-timers the fun has just begun. With an average age of 82, the city's oldest band took to the stage, as they had done every night for the past four decades.

What's their secret to a long life?

"Music! Without music, a part of life would be missing," 87-year-old Mao Xiangjie told me.  

Shanghai's enduring elders are testament to just how much China's living standards have improved over the past 70 years. And with more efforts to boost public health in particular, chances are this band could have more years left in it yet.