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Typically, test scores are obtained at an early age, and compared to later morbidity and mortality. In addition to exploring and establishing these associations, cognitive epidemiology seeks to understand causal relationships between intelligence and health outcomes. Researchers in the field argue that intelligence measured at an early age is an important predictor of later health and mortality differences.
Overall mortality and morbidity[edit | edit source]
A strong inverse correlation between early life intelligence and mortality has been shown across different populations, in different countries, and in different epochs." Various explanations for these findings have been proposed:
"First, ...intelligence is associated with more education, and thereafter with more professional occupations
that might place the person in healthier environments. ...Second, people with higher intelligence might engage in more healthy behaviours. ...Third, mental test scores from early life might act as a record of insults to the brain that have occurred before that date. ...Fourth, mental test scores obtained in youth might be an indicator of a well-put-together system. It is hypothesized that a well-wired body is more able to respond effectively to environmental insults..."
People with higher IQ test scores tend to be less likely to smoke or drink alcohol heavily. They also eat better diets, and they are more physically active. So they have a range of better behaviours that may partly explain their lower mortality risk.—-Dr. David Batty
The strong correlation between intelligence and mortality has raised questions as to how better public education could delay mortality.
Research in Scotland has shown that a 15-point lower IQ meant people had a fifth less chance of seeing their 76th birthday, while those with a 30-point disadvantage were 37% less likely than those with a higher IQ to live that long.
Coronary heart disease[edit | edit source]
Among the findings of cognitive epidemiology is that men with a higher IQ have less risk of dying from coronary heart disease. The association is attenuated, but not removed, when controlling for socio-economic variables, such as educational attainment or income. This suggests that IQ is an independent risk factor for mortality.
Psychiatric[edit | edit source]
Post-Traumatic Stress Disorder, severe depression, and schizophrenia are less prevalent in higher IQ bands. On the other hand, higher IQ persons show a higher prevalence of Obsessive Compulsive Disorder.
The Archive of General Psychiatry published a longitudinal study of a randomly selected sample of 713 study participants (336 boys and 377 girls), from both urban and suburban settings. Of that group, nearly 76 percent had suffered through at least one traumatic event. Those participants were assessed at age 6 years and followed up to age 17 years. In that group of children, those with an IQ above 115 were significantly less likely to have Post-Traumatic Stress Disorder as a result of the trauma, less likely to display behavioral problems, and less likely to experience a trauma. The low incidence of Post-Traumatic Stress Disorder among children with higher IQs was true even if the child grew up in an urban environment (where trauma averaged three times the rate of the suburb), or had behavioral problems.
Dementia[edit | edit source]
A decrease in IQ has also been shown as an early predictor of late-onset Alzheimer's Disease and other forms of dementia. In a 2004 study, Cervilla and colleagues showed that tests of cognitive ability provide useful predictive information up to a decade before the onset of dementia.
However, when diagnosing individuals with a higher level of cognitive ability, a study of those with IQ's of 120 or more, patients should not be diagnosed from the standard norm but from an adjusted high-IQ norm that measured changes against the individual's higher ability level.
In 2000, Whalley and colleagues published a paper in the journal Neurology, which examined links between childhood mental ability and late-onset dementia. The study showed that mental ability scores were significantly lower in children who eventually developed late-onset dementia when compared with other children tested.
Behavior[edit | edit source]
In terms of the effect of one's intelligence on health, in one British study, high childhood IQ was shown to correlate with one's chance of becoming a vegetarian in adulthood. In another British study, high childhood IQ was shown to inversely correlate with the chances of smoking.
A study of 11,282 individuals in Scotland who took intelligence tests at ages 7, 9 and 11 in the 1950s and 1960s, found an "inverse linear association" between childhood intelligence and hospital admissions for injuries in adulthood. The association between childhood IQ and the risk of later injury remained even after accounting for factors such as the child's socioeconomic background.
References[edit | edit source]
- Deary IJ and Batty GD (2007). Cognitive epidemiology. J. Epidemiol. Community Health 2007;61;378-384.
- Deary IJ (2009). Introduction to the special issue on cognitive epidemiology. Intelligence 37, Issue 6, November–December 2009, 517-519.
- Deary, Ian (2008). Why do intelligent people live longer?. Nature 456 (7219): 175–176.
- Kirsten, Traynor (December 13, 2010). Old and Wise. Scientific American Mind (November 2010).
- Adolescent IQ and Survival in the Wisconsin Longitudinal Study. CDE Working Paper No. 2010-05. Center for Demography and Ecology. URL accessed on 22 November 2010.
- Marmot, M., M. Kivimaki (2009). Social inequalities in mortality: a problem of cognitive function?. European Heart Journal 30 (15): 1819–1820.
- includeonly>"People with higher IQs live longer - Telegraph", The Daily Telegraph, 2:22PM GMT 16 Mar 2009. Retrieved on 22 November 2010.
- Study of one million Swedes uncovers link between IQ and risk of death - insciences. In Sciences Organisation. URL accessed on 22 November 2010.
- High IQ Linked To Reduced Risk Of Death. ScienceDaily. URL accessed on 22 November 2010.
- includeonly>Henderson, Mark. "Brighter people live longer, says Glasgow scientist David Batty - Times Online", The Times, July 15, 2009. Retrieved on 22 November 2010.
- Deary, Ian J., Alexander Weiss and G. David Batty (July 2011). Outsmarting Mortality. Scientific American Mind: 48–55.
- Whalley LJ, Deary IJ (April 2001). Longitudinal cohort study of childhood IQ and survival up to age 76. BMJ 322 (7290).
- David G Batty, Martin J. Shipley, Laust H. Mortensen, Catharine R. Gale, Ian J. Deary. IQ in late adolescence/early adulthood, risk factors in middle-age and later coronary heart disease mortality in men: the Vietnam Experience Study. European Journal of Cardiovascular Prevention & Rehabilitation 14 (3): 359–361.
- PMID 20704978 (PMID 20704978)
- (2006). Intelligence and Other Predisposing Factors in Exposure to Trauma and Posttraumatic Stress Disorder: A Follow-up Study at Age 17 Years. Archives of General Psychiatry 63 (11): 1238–45.
- (2007). Association between the DTNBP1 gene and intelligence: a case-control study in young patients with schizophrenia and related disorders and unaffected siblings. Behavioral and Brain Functions 3 (1).
- (2008). Premorbid IQ in Schizophrenia: A Meta-Analytic Review. American Journal of Psychiatry 165 (5): 579–87.
- Breslau N, Lucia VC, Alvarado GF (November 2006). Intelligence and other predisposing factors in exposure to trauma and posttraumatic stress disorder: a follow-up study at age 17 years. Arch. Gen. Psychiatry 63 (11): 1238–45.
- Cervilla J, Prince M, Joels S, Lovestone S, Mann A (August 2004). Premorbid cognitive testing predicts the onset of dementia and Alzheimer's disease better than and independently of APOE genotype. J. Neurol. Neurosurg. Psychiatr. 75 (8): 1100–6.
- Dorene Rentz, Brigham and Women's Hospital's Department of Neurology and Harvard Medical School. More Sensitive Test Norms Better Predict Who Might Develop Alzheimer's Disease. Neuropsychology, published by the American Psychological Association. URL accessed on August 6, 2006.
- Whalley LJ, Starr JM, Athawes R, Hunter D, Pattie A, Deary IJ (November 2000). Childhood mental ability and dementia. Neurology 55 (10): 1455–9.
- (2006). IQ in childhood and vegetarianism in adulthood: 1970 British cohort study. BMJ 334 (7587).
- (2005). Childhood IQ and social factors on smoking behaviour, lung function and smoking-related outcomes in adulthood: Linking the Scottish Mental Survey 1932 and the Midspan studies. British Journal of Health Psychology 10 (3): 399–401.
- Lawlor DA, Clark H, Leon DA (February 2007). Associations between childhood intelligence and hospital admissions for unintentional injuries in adulthood: the Aberdeen Children of the 1950s cohort study. Am J Public Health 97 (2): 291–7.
Further reading[edit | edit source]
- Alexander, Brian Brainy guy, better sperm? Take that, tough guy!. MSNBC. URL accessed on 30 December 2008.
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