Deborah Kotz, Globe Staff
After a three-decade tripling in childhood obesity rates, the trend has leveled off and, for the first time, appears to be on a substantial decline - at least among Massachusetts infants and preschoolers, according to a study published Monday in the journal Pediatrics.
Researchers at the Harvard Pilgrim Health Care Institute found that the percentage of obese girls under age 6 dropped from 9 percent to slightly more than 6 percent from 2004 to 2008; the percentage of obese boys under age 6 fell from nearly 11 percent to just under 9 percent during the same time period.
“This is a surprising and encouraging finding,’’ said study leader Dr. Xiaozhong Wen, a postdoctoral fellow at Harvard Pilgrim.
The study analyzed electronic medical records of nearly 37,000 children from birth to age 5 in Harvard Vanguard Medical Associates’ pediatric practice group in Eastern Massachusetts. The positive results could indicate that increasing public awareness about the dangers of childhood obesity and state health programs to prevent it could finally be paying off.
The next step, Wen said, is “to figure out what led to this decline and whether it’s a national trend.’’
A 2010 national government survey detected a slight decline in obesity rates among preschoolers in recent years but didn’t contain a large enough sample of young children to determine whether it was a true statistical trend. Another national study did not find any drop in rates but that could be because it included only youngsters from low-income families who have traditionally higher obesity rates.
The latest study found the same glaring discrepancy between those from high-income and low-income families: Children on Medicaid - coverage provided to those near the poverty level - had obesity rates that dropped on average from 12.3 percent to 11.5 percent, a change small enough to be due to statistical chance. Those covered by other health plans had a more significant decline in obesity rates from 10.1 percent to 8.3 percent.
“There’s a subgroup population of kids who don’t seem to be experiencing the same benefit of positive movement as others,’’ said Dr. Lauren Smith, the state public health department’s medical director. “We have to always be cognizant and cautious that interventions that we’re doing are equitably distributed across all populations at risk so we don’t exacerbate disparities.’’
