However, a 2020 study by sociologist Hui Zheng suggests that early U.S. Baby Boomers (born between the late-1940s and early-1950s) and middle Baby Boomers (born between the mid- to late-1950s) suffered from significant cognitive decline at age 50 and over compared to their elders, even though the generations born before and during the Second World War had increasing cognitive scores from one generation to the next when they were at the same age. "Baby boomers already start having lower cognition scores than earlier generations at age 50 to 54," Zheng noted. There are a variety of factors associated with the cognitive decline of Baby Boomers relative to older generations: psychological depression and other mental health problems, lower rates of marriage (at the time of the study), having multiple marriages, physical inactivity, obesity, cardiac issues, strokes, and diabetes. What Zheng found surprising, was that even though many other health problems were negatively correlated with wealth and educational attainment, wealthy and highly educated Baby Boomers fared little better than their counterparts with lower levels of income or education.