The surprising finding, made by a University of Michigan Health System team as part of a family health study that followed 257 boys and their parents for 10 years, held true even after other issues such as depression, aggression, attention problems and parental alcoholism were taken into account. Long-term data on girls are not yet available.
Based on their result, the researchers suggest that early sleep problems may be useful as a "marker" for predicting later risk of early adolescent substance use -- and that there may be a common biological factor underlying both traits. The relationship between sleep problems and the use and abuse of alcohol in adults is well known, but this is the first study to look at the issue in children.
They also emphasize that parents should take the finding only as one more reason to focus on healthy sleep habits for their children -- not as a reason to worry.
The findings will be published in the April issue of Alcoholism: Clinical and Experimental Research by a team from the U-M Addiction Research Center (UMARC), in the Department of Psychiatry, and a colleague from Michigan State University.
The data come from an ongoing longitudinal project that uses interviews and standardized research questionnaires to look at mental and physical health issues in families over the long term. The study was recently extended for another 10 years, with further funding from the National Institutes of Health in the form of a MERIT Award.
"What's so interesting about this finding is that the effect exists regardless of a number of other factors that previously had been identified as relating to risk for substance use and abuse," says senior author and UMARC director Robert Zucker, Ph.D. "It appears to indicate some shared neurobiological dysfunction whose details we don't yet know. Further studies will be crucial to our understanding."
"Taken together with other studies in this area, our findings help make up a chain of evidence linking sleep disturbances to alcohol problems across a large segment of the life span," says lead author and research assistant professor Maria Wong, Ph.D.
The finding does not mean there's a cause-and-effect relationship, notes co-author and psychiatry professor Kirk Brower, M.D., who has studied the interplay of alcohol and sleep in adults, and is Executive Director of the Chelsea Arbor Treatment Center, which treats teen and adult substance abusers. (Chelsea Arbor is a joint program of U-M and Chelsea Community Hospital.)
"Our finding sees early childhood sleep disturbances as a marker, or predictor, for early use of drugs and alcohol in adolescence, not a predetermined trajectory," he says. "But for parents, this is one more reason to take your child's sleep problems seriously, not to dismiss them, and to talk with your child's pediatrician or family doctor."
The new study extends into early childhood the growing knowledge about how sleep and sleep disorders relate to alcohol use and alcoholism, drug use and abuse, and tobacco use. For instance, alcoholics and non-alcoholic adults often use alcohol to try to help them sleep – even though their slumber is often disrupted when the alcohol wears off, and the amount of alcohol needed to make them sleepy grows over time as they develop a tolerance. And people with insomnia are far more likely than others to abuse alcohol, smoke and develop drug habits.
Also, several studies based on one-time interviews of teens have shown a high co-incidence of sleep problems and drug and alcohol use, although depression or aggression appeared to account for some of the effect. But the studies' designs don't allow study of causal relationships.
The new U-M study looked at data taken at three points in the boys' lives:
- Ages 3-5 – The boys' mothers were asked to report whether their sons had trouble sleeping, or were overtired during the day, using the widely-used, well-validated Child Behavior Checklist (CBCL). Their answers to these two items were looked at individually, and as a combined data point labeled "sleep problems." The researchers also assessed whether either of the child's parents met the definition for alcoholism in the last three years.
- Ages 9-11 – The mothers were again asked to use the CBCL to assess their sons' attention problems, level of anxiety or depression symptoms, and aggressive behavior characteristics. All three areas of behavior problems have been linked with sleep problems and/or with drug and alcohol use and abuse.
- Ages 12-14 – The boys were asked to take the Drinking and other Drug Use History Questionnaire (DDHQ-Y) developed and validated by Zucker and MSU psychologist Hiram Fitzgerald, Ph.D. The anonymous questionnaire asked the young teens to report how old they had been when they first took a drink of alcohol bigger than a sip, how old they had been when they first got drunk, if they had ever smoked cigarettes and how often, and how many times they had used marijuana, inhalants, cocaine, steroids and other illicit drugs.
In all, one-third of the children were reported to have had a sleep problem in early childhood, whether trouble sleeping, overtiredness, or both. Sixty percent of the children had one parent with an alcohol problem, reflecting the larger study's weighted population. All of the children lived with both parents, and all were Caucasian. The children were from similar economic backgrounds.
By age 12 to 14, about 32 percent of the boys had started drinking alcohol, and 40 percent of that group had been drunk at least once. About one-tenth regularly smoked cigarettes, and 17 percent had used at least one kind of illicit drug.
There was no connection between parental alcoholism and children's sleep problems or behavior issues. But children of alcoholics were, as expected, more likely to have started using alcohol and drugs early in adolescence. This kind of family-associated risk is well known to exist.
The link between sleep problems and substance use was clear, even after controlling for parental alcoholism. Boys with early-childhood sleep problems were 2.3 times more likely to have started using alcohol by age 14, and 2.3 times more likely to smoke cigarettes occasionally or regularly, than boys whose mothers hadn't cited sleep problems.
They were also 2.6 times more likely to have used marijuana, and 2.2 times more likely to have used illicit drugs. The only issue to which sleep problems weren't significantly linked was the first time the boys had gotten drunk.
The researchers re-analyzed the data to examine whether the relationship between sleep problems and the early onset of substance use was in part due to the presence of attention problems, aggression and anxiety/depression. Although early childhood sleep problems predicted attention problems and anxiety/depression in late childhood, these problems did not predict the onset of substance abuse independent of sleep problems.
The researchers note that early onset of alcohol use is known to be linked to a higher risk of later alcohol abuse and dependence, as well as injuries, violence and drunk-driving. If sleep problems in early childhood might be a useful marker to signal an increased risk of early substance use, they note, sleep problem screenings could help identify children who could be at risk.
And, they say, the fact that children's sleep habits can be improved by careful attention from parents and doctors means that there's some chance the long-term risk could be addressed.
"Parents should pay attention to their children's complaints about insomnia and overtiredness," says Wong. "If necessary, they should discuss those problems with their child's health care provider. They should also set a regular sleep schedule for their child, ensure they get adequate amounts of sleep, and encourage their children to engage in relaxing, not stimulating, activities before bed."
Wong and her colleagues will continue analyzing data from the family study to look for further patterns in girls, and as the boys grow older. They also hope to use wrist-band movement monitors and brain-activity sleep tests called polysomnography to study the issue further.
Reference: Sleep problems in early childhood and early onset of alcohol and other drug use in adolescence; Alcoholism: Clinical and Experimental Research, April 2004.