An ageing population has fuelled a rise in cancer and contributed to a doubling in breast and lung cancer cases in the past 30 years, researchers said on Thursday.

But rates of stomach and Cervical cancer have fallen thanks to improved hygiene and screening programmes.

“Cancer is increasing rapidly and this is due mainly to the changing demographics of the world population,” Lucy Boyd, of the charity Cancer Research UK, which compiled the report, told Reuters.

As people get older they are more likely to develop cancer. The rise in breast cancer cases, from half a million in 1975 to more than 1.1 million cases worldwide is due to women living longer and a growing world population.

The scientists analysed statistics from the International Agency for Research on Cancer (IARC) database and compared incidence and death rates in different regions of the world. They predict cases of lung cancer, the biggest cancer killer, will soar in developing countries in coming decades.

Lung cancer rates tend to rise decades after the number of smokers has peaked. In areas of the world such as eastern Africa, central America and southeast Asia where the number of smokers has risen lung cancer cases are expected to increase over the next 20 years.

The developed world has historically had high rates of cancer but Boyd said smoking and changes in diet are expected to push up rates of cancer in poorer countries.

Each year 10.9 million people worldwide are diagnosed with cancer and 6.7 million die from the disease. About 12 percent of deaths worldwide are due to cancer, according to the report.

Male cancer rates are highest in the United States, Hungary and New Zealand and are lowest in Niger, Gambia and the Congo.

The United States also has the highest rate of female cancers along with Israel and New Zealand. By contrast, Tunisia, Gambia and Oman have the lowest.

Lung, breast, bowel, stomach, prostate, cervical and oesophageal are the most commonly diagnosed cancers. Lung, stomach and liver are the biggest killers.

Professor John Toy, the medical director of the charity, said cancer is still mainly a disease of the developed world.

“Only four percent of deaths in Africa are due to cancer, compared to 19 percent in Europe,” he said.

“Although these figures show a persistent increase in the number of people in the world being diagnosed with cancer, developing and refining new treatments will continue to improve the chances of surviving the disease,” he added.