(Vahid Salemi/Associated Press)

Research published Monday afternoon in the Archives of Internal Medicine suggests that chronic exposure to airborne particulate matter — small solid particles suspended in air — is associated with increased risk of cognitive impairment. The greater the exposure (in this study, over a four-year period), the study finds, the faster the cognitive decline.

That cognitive impairment can be a stepping stone toward dementia and to Alzheimer’s disease, which currently affects an estimated 5.1 million people in the United States.

The study paired data from the Nurses’ Health Study Cognitive Cohort (which features 14 years worth of data for more than 19,000 U.S. women ages 70 to 81, starting in 1988) with geographical information about pollution levels in participants’ locales. They found that exposure to both small and large particulates was associated with sizable cognitive losses. The authors say theirs is the first study to look at the effects of small as well as large particles in the ambient air.

The link held equally for areas with lots of fine particulate matter and for those with lots of larger particles in the air. The air pollution levels were comparable to those found in many areas throughout the United States, the study notes.

Particulate matter air pollution has already been tied to cardiovascular and respiratory ills.

The study concludes that if their findings are borne out through further research, reducing particulate air pollution might emerge as a means of lessening the burden of cognitive impairment and dementia.

A related commentary suggests that political and regulatory actions may be the best means of reducing the burden of particulate air pollution.