"Contrary to assumptions related to earlier studies, our research suggests that ultra-clean, ultra-hygienic environments early in life may contribute to higher levels of inflammation as an adult, which in turn increases risks for a wide range of diseases," lead study author Thomas McDade, associate professor of anthropology in Northwestern University's Weinberg College of Arts and Sciences and the Institute for Policy Research, says in a statement.
McDade suggests exposure to infectious microbes early in life may protect individuals from cardiovascular diseases that can lead to death as an adult.
The research suggests that inflammatory systems may need a higher level of exposure to common everyday bacteria and microbes to guide their development.
The researchers used data from the longitudinal study of Filipinos that tracked participants in utero through age 22.
The researchers examined C-reactive protein production -- a protein that rises due to inflammation -- and a risk factor for heart disease. The Philippines have a high level of infectious diseases in early childhood compared to Western countries.
Blood tests showed that C-reactive protein was at least 80 percent lower for study participants in the Philippines when they reached young adulthood, relative to their American counterparts, McDade says.