People are developing dementia a decade before they were 20 years ago, perhaps because of environmental factors such as pollution and the stepped-up use of insecticides, a wide-ranging international study has found.

The study, which compared 21 Western countries between the years 1989 and 2010, found that the disease is now being regularly diagnosed in people in their late 40s and that death rates are soaring.

The study was published in the Surgical Neurology International journal, and its findings publicized in the London Times newspaper Thursday.

The problem was particularly acute in the United States, where neurological deaths in men aged over 75 have nearly tripled and in women have risen more than fivefold, the leader of the study, Colin Pritchard from Bournemouth University, told the London Times.

Scientists quoted in the study said a combination of environmental factors such as pollution from aircraft and cars as well as widespread use of pesticides could be the culprit, the newspaper reported.

Early onset dementia used to cover people developing the disease in their late 60s. Now, it’s meant to mean people much younger than that, the research showed.

The scientists said nobody wanted to put an end to modern advances, but asserted the need to make them safer.