Living under communism makes countries poorer and less healthy for decades, according to a landmark new study.

Researchers testing historical connections between cultures found that whether a country had been under communism was the biggest factor for those with lower health, income and educational levels.

In the first undertaking of its kind, they analyzed the fortunes of 44 countries across Europe and Asia and looked at geography, religion, systems of government and a more intangible quality called “deep cultural ancestry.”

Writing in the journal Royal Society Open Science, they matched these factors against where they ranked on the United Nations Human Development Index, which measures per-capita income, life expectancy at birth and the number of years its citizens spend in education.

Most of the issues they looked at appeared to have little or no effect on the disparities between the countries, except for Islamic countries scoring a little worse on education.

Instead, the single strongest predictor for a country’s health, and the second-strongest for its wealth, turned out to be whether its rulers had embraced communism.

The study said that after World War II, economic growth in Communist Eastern Europe was slower than in the West, but despite the Soviet Union’s collapse almost 30 years ago, the effects are still being felt.

The study says that communism was also behind the stagnation of life expectancy behind the Iron Curtain during the 1970s and 1980s, which has set those countries back even today.

The researchers say: “The proximate causes for this low life expectancy are complex, but high alcohol consumption, smoking and poor workplace safety, as well as low-quality diet and living conditions associated with lower income levels are implicated.”