University of Iowa researchers have released first-year findings of a $1 million state-funded study into Iowa’s high cancer rates: demographics and lifestyle explain 76 percent of excess cases for the five most common cancers.

The five cancers — prostate, breast, lung, colorectal and melanoma — make up 55 percent of new cases in Iowa. Smoking, heavy drinking, obesity, age, race and radon levels explained 697 of the 921 excess cases.

But the 76 percent figure covers only those five cancers. When all cancer types are included, the study explains only about 35 percent of Iowa’s excess cases.

Iowa averaged about 2,001 more cancer diagnoses a year than expected between 2018 and 2022. About 1,304 extra cases a year were not studied in depth or could not be explained.

“Things like prostate cancer, postmenopausal breast cancer, there’s some mystery left to those,” said lead researcher Mary Charlton, a University of Iowa public health professor.

The second year of the project, funded with federal dollars, will examine genetic and environmental risk factors. Governor Kim Reynolds highlighted the findings, saying the research connected “76% of our state’s excess cancer cases to behavioral and demographic factors”.