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Children with high IQs live longer, but it is not clear exactly what role IQ plays in longevity, new British research shows.
Previous studies have shown an association between IQ and mortality, but an explanation for that has proved elusive. This is an important question because identifying those mechanisms would help in understanding the origins of health inequalities, the researchers said.
"The IQ-mortality association emerges already early in adult life, even when most life-threatening diseases are not yet that common," said lead researcher Markus Jokela, who is now with the department of psychology at the University of Helsinki, in Finland. "So the role of IQ is not only restricted to how people become ill or cope with their illnesses in old age."
The report is published in Paediatrics.
Data from 1958 study
For the study, Jokela's team collected data on 10,620 men and women who participated in the 1958 British Birth Cohort Study and had their IQs tested when they were 11. Researchers followed these individuals until they were 46 years old.
The investigators found that IQ assessed in childhood at age 11 predicted mortality risk from age 11 to age 46, so that the risk of dying by midlife was about two times higher in individuals with low IQs compared to those with high IQs (3.4% versus 1.7%, respectively).
This association was largely independent of several measures of childhood developmental characteristics and family background such as birth weight, childhood height at age 11, problem behaviour, father's occupation, parents' interest in child's education, family size and family difficulties, Jokela said.
Adult sociodemographic variables such as education, occupation, marital status and health behaviours such as smoking, weight, alcohol use and psychosomatic symptoms "explained only relatively little of the IQ-mortality association," he said.
IQ a determinant of health and mortality
"The findings imply that IQ is an important determinant of health and mortality risk independently of many well-established health risk factors," Jokela said. "This calls for new lines of research identifying the mechanisms by which IQ becomes associated with health and mortality risk."
Perhaps individuals with high IQ are better at distilling important health information from public health messages and thereby better in making healthy everyday choices that are not captured by the usual measures of health behaviours, Jokela said.
"We currently have an incomplete understanding of health inequalities originating from individual psychological characteristics, such as IQ," he said. "Identifying these mechanisms could inform us how to plan more effective public health interventions accessible to wider audiences."
Nurturing parents key to long life
Ellen deLara, an assistant professor of social work at Syracuse University, thinks that nurturing parents may be the key to living longer, regardless of IQ.
"Positive adult/parental attention is typically a contributor to positive youth outcomes in terms of development and behaviour," deLara said. "This applies across the board to all youth, all socioeconomic groups, all levels of intelligence."
Conversely, negative adult attention in the form of rejection or neglect, for example - something that some parents exhibit towards lower IQ children - is associated with poor outcomes for these children in terms of their development, and their childhood and adult behaviour, she said.
"What it boils down to is, no matter your IQ, if you feel accepted - your parents are interested in your education and your future - you thrive," deLara said.
"If you feel that you are rejected - your parents show little or no interest in you or your future - you don't feel good about yourself," she said. "That in itself, promotes poor decision-making. If your decision-making ability is already compromised by lower IQ, this does not bode well for a successful or long life." - (Steven Reinberg/HealthDay News, August 2009)
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