Rates of childhood asthma appear to have plateaued, except among the poor and kids aged 10 to 17, according to a CDC study published in the journal Pediatrics.

Researchers found that childhood asthma rates increased from 2001 to 2009 — a trend that began in 1982. The rate peaked in 2009 at close to 10%, then leveled off before dropping to slightly more than 8% in 2013.

“This is mainly due to the leveling off of prevalence among black children, who previously had large increases in the prevalence of asthma,” said lead researcher Dr Lara Akinbami with the CDC’s National Center for Health Statistics.

Among children who are living in families with income below the poverty level and those aged 10 to 17, researchers found that asthma rates increased between 2001 and 2013. Among white and Puerto Rican children, the prevalence of asthma remained the same from 2001 to 2013. Puerto Rican children had the highest prevalence of asthma compared with all other groups.