LONDON -- Drugmaker Astrazeneca is hoping scientific secrets in the world's biggest register of twins will help isolate the environmental and genetic roots of diseases like cancer and eventually lead to a cure.

The Anglo-Swedish firm said on Wednesday it had signed a deal with Swedish Medical University, the Karolinska Institute, to gain access to its database of 120,000 twins born since 1886.

The institute has been collecting medical histories since the 1950s and now plans to add genetic data through blood samples.

Such work is a sensitive matter in a country that, like Nazi Germany, embraced eugenics, a discredited theory to improve the human race by selective breeding. Between 1935 and 1975 Swedish doctors sterilized some 63,000 people considered racially inferior, including the mentally ill, alcoholics and criminals.

Astrazeneca said it and the Karolinska Institute were adhering to time-honored ethical principles and following strict guidelines on disclosure and patient consent.

"Astrazeneca prides itself on its ethical research and development methods," a spokeswoman said.

Karolinska's president Hans Wigzell said: "As we enter the 21st century, it is only appropriate that we expand the registry to include genetic information so that the registry can contribute to the advancement of medical research, which promises to usher in a new wave of discoveries in human health." The hope is that information in the Karolinska Institute's database will help scientists isolate the environmental and genetic factors that cause a whole range of diseases, including cancers, Alzheimer's and heart disease.

Identical twins have identical genetic codes. If one twin suffers from an illness and the other is spared, scientists can look to environmental influences.

In non-identical twins, the genetic codes are no more similar than those between siblings. Here researchers can try to isolate a particular gene as the cause of an illness.

"For us it's really going to help us...in terms of targeting drugs towards a particular gene that might be responsible for a disease," Reuters quoted the Astrazeneca spokeswoman as saying.

In return for access to the register, astrazeneca will provide the Swedish twin registry with a grant to fund the archive for five years and additional research expertise.

Research into twins was an obsession at the height of the eugenics craze. Nazi doctor Josef Mengele, trying to breed a pure German race, carried out grotesque experiments on prisoners in Auschwitz Concentration Camp.

In the late 19th century it was Francis Galton, Charles Darwin's cousin, who first thought of using twins to investigate the differences between people. He also coined the term eugenics, which captivated thinkers on the left and right of politics in the first half of the 20th century.

In recent years, all major drugs companies have invested heavily in gene research in order to develop a new generation of personalized therapies to match the genetic makeup of patients.