The analysis also found that significant health disparities exist between racial groups, and that Americans are less likely to have access to health care when they reach adulthood than they did during the teenage years.
The analysis appears in the January 2006 Archives of Pediatrics and Adolescent Medicine and was conducted by researchers at the Carolina Population Center and the University of North Carolina at Chapel Hill.
"Smoking, obesity, and alcohol abuse are leading contributors to preventable death in the United States," said Duane Alexander, M.D., director of the National Institute of Child Health and Human Development, the NIH Institute that funded the analysis. "By early adulthood, a large proportion of Americans smoke, are overweight, and drink alcohol to excess."
Principal investigator Kathleen Mullan Harris, Ph.D., and her colleagues of the Carolina Population Center and the University of North Carolina at Chapel Hill, conducted their analysis using data from the National Longitudinal Study of Adolescent Health.
The National Longitudinal Study of Adolescent Health was designed to measure the effects of home, family, and school environment on behaviors that promote health. The study was undertaken in response to a mandate by Congress. Funding for the survey was provided by a grant from the NICHD with contributions from 17 other federal agencies.
"When they were young teenagers, most of the participants had fairly healthy behaviors," said Christine Bachrach, Ph.D., Chief of NICHD's Demographic and Behavioral Sciences Branch and project officer for the study. "What's really alarming is how rapidly healthy practices declined by the time the participants reached young adulthood."
For the current analysis, the researchers analyzed the responses of a nationally representative sample of more than 14,000 young adults who have been followed since early adolescence. The survey respondents, recruited from high schools and middle schools around the country, were first interviewed from 1994 to 1995, when they ranged from 12 to 19 years of age, and again in 2001 and 2002, when they were 19 to 26 years old.
The survey participants responded to questions on diet, inactivity, obesity, tobacco use, substance use, binge drinking, violence, reproductive health, mental health, and access to health care.
For nearly all groups surveyed, diet, activity level, obesity, health care access, tobacco, alcohol and illicit drug use, and likelihood of acquiring a sexually transmitted disease worsened as the youth reached adulthood, Dr. Harris said.
"These trends are quite stunning," Dr. Harris added. "Whether or not the trends will continue as they age, we don't know. But it doesn't bode well for their future health, especially if these habits become established."
By the time they had reached adulthood, Dr. Harris explained, the participants were more likely to be obese, to frequently eat fast food, and to be sedentary. They were also less likely to have health insurance, to receive health care when they needed it, or to receive regular dental and physical health examinations.
The authors reported "dramatic" increases in behaviors related to 3 leading contributors to preventable deaths. "These findings underscore the importance of ongoing preventive efforts related to smoking, poor diet and physical inactivity, and alcohol consumption, early in the life course."
For example, among young white women, the proportion reporting no weekly physical exercise was 5 percent during the adolescent years, but was 46 percent in early adulthood. Similarly, among white males, the proportion that was obese grew from 14 percent in the teen years to 19 percent when they became adults.
The researchers added that the decline in health care coverage resulted from young adults leaving their parents' health insurance or Medicaid coverage as they reached legal age.
On the positive side, participants were less likely to experience feelings of depression at adulthood than when they were adolescents, less likely to have suicidal thoughts, and less likely to be victims or perpetrators of violence.
For most of the indicators, Asians and whites were at lowest risk, while blacks and Native Americans were at highest risk. Racial and ethnic disparities in health as well as in access to health care also increased as the participants reached adulthood. No single racial or ethnic group, however, had a greater overall risk profile than any other group.
Whites, for example, were healthier during earlier adolescence than most other groups, but experienced the greatest declines upon reaching adulthood. By the time they reached adulthood, whites had the highest rates of smoking (31 percent for males, 28 percent for females) and white males had the highest rate of binge drinking (67 percent).
At adulthood, blacks were the least likely to smoke cigarettes (13 percent for males, 8 percent for females) to binge drink (33 percent for males, 15 percent for females) or to use hard drugs (5 percent for males, 2 percent for females). When they were adults, blacks (18 percent) and Native Americans (16 percent) were more likely to develop asthma than were other groups.
Among female adults, blacks (55 percent) and Asians (53 percent) were the least likely to exercise, and among males, white and blacks were the least likely to exercise.
Dr. Harris explained that she and her coworkers are now doing additional research on the data in the Adolescent Health study to determine why certain groups were more at risk for a particular unhealthy behavior than other groups. She added, however, that because the groups differed in their health behaviors, intervention programs to reduce unhealthy behaviors would likely have the greatest chances for success if they were individually tailored to meet the needs of each particular group.
"The variability in health disparities among groups also implies that no one overall solution will work to reduce disparities, but approaches specific to each health outcome are needed," Dr. Harris said
The NICHD is part of the National Institutes of Health (NIH), the biomedical research arm of the federal government. NIH is an agency of the U.S. Department of Health and Human Services. The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation.