Cancer rates in north China's port city Tianjin have increased more than 40 percent over the past two decades, which researchers say is mainly because the ratio elderly people has more than doubled.

The research conducted by the Chinese Academy of Engineering in Tianjin, which has a population of 4 million, shows that the number of people who contract cancer increased from 177 per 100,000 to 245 per 100,000 over the past 20 years.

The number of new cancer patients rose at an annual rate of 3.3 percent, according to the research, which has resulted in establishing the largest malignant tumor monitoring system in China.

Along with cancer rates, the average age of Tianjin resident also increased significantly. People over the age of 65 account for 12.62 percent of the city's population, compared with 5.75 percent 20 years ago. The average age of residents jumped seven years over the last two decades.

The research found that 55.35 percent of people over the age of 65 had contracted cancer.

The most deadly types of cancer in men are lung, liver and intestinal while women suffered most from breast, lung and intestinal cancers, according to the research.

Researchers said the major causes of cancer include smoking, a diet higher in animal fat, obesity and a lack of exercise.