IQ & Health
According to the World Health Organization, people further down the social ladder usually run at least twice the risk of serious illness and premature death of those near the top.
A possible explanation has been proposed in several papers by Linda Gottfredson and Ian Deary. The crucial points are that (a) social status correlates strongly and positively with IQ and other measures of intelligence; (b) intelligence correlates strongly with “health literacy,” the ability to understand and follow a prescription for disease prevention and treatment; and (c) intelligence is also correlated with forward planning — which means avoidance of health risks (including smoking) as they are identified.
In modern developed countries IQ correlates about 0.5 with measures of income and social status. The mean IQ of Americans in the Census Bureau’s “professional and technical” category is 111. The mean for unskilled laborers is 89. An American whose IQ is in the range between 76 and 90 is 8 times as likely to be living in poverty as someone whose IQ is over 125.
Intelligent people tend to be the most knowledgeable about health-related issues. In the past big gains in health and longevity were associated with improvements in public sanitation, immunization and other initiatives not requiring decisions by ordinary citizens. But today the major threats to health are chronic diseases — which require patients to participate in the treatment.
Deary was coauthor of a 2003 study in which childhood IQs in Scotland were related to adult health outcomes. Mortality rates were 17% higher for each 15-point falloff in IQ. Gottfredson cites a 1993 study indicating that more than half of the 1.8 billion prescriptions issued annually in the U.S. are taken incorrectly. The same study reported that 10% of all hospitalizations resulted from patients’ inability to manage their drug therapy.
A new Test of Functional Health Literacy of Adults can evaluate the problem in a mere 22 minutes. In a sample of 2,659 clinic patients in two urban hospitals, 42% did not understand the instructions for taking medicine on an empty stomach, and 26% did not understand when the next appointment was scheduled.
Smoking, obesity and sedentary living are more prevalent among the low-status. A 2001 study by the Centers for Disease Control & Prevention found that college graduates are 3 times as likely to live healthily as those who never got beyond high school.