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.
OBJECTIVE
To investigate the associations of childhood IQ and adult social factors, and smoking behaviour, lung function (forced expiratory volume in one second; FEV(1)), and smoking-related outcomes in adulthood.


METHODS
Retrospective cohort study.


METHODS
Participants were from the Midspan prospective studies conducted on Scottish adults in the 1970s. The sample consisted of 938 Midspan participants born in 1921 who were successfully matched with their cognitive ability test results on the Scottish Mental Survey 1932.


RESULTS
Structural equation modelling showed that age 11 IQ was not directly associated with smoking consumption, but that IQ and adult social class had indirect effects on smoking consumption via deprivation category. The influence of IQ on FEV(1) was partly indirect via social class. Gender influenced smoking consumption and also IQ and social class. There was a 21% higher risk of having a smoking-related hospital admission, cancer, or death during 25 years of follow-up for each standard deviation disadvantage in IQ. Adjustment for adult social class, deprivation category, and smoking reduced the association to 10%.


CONCLUSIONS
Childhood IQ was associated with social factors which influenced lung function in adulthood, but was not associated directly with smoking consumption. In future studies, it is important to consider other pathways which may account for variance in the link between childhood IQ and health in later life.
Taylor
Michelle D
MD
Department of Psychology, University of Edinburgh, UK.
Hart
Carole L
CL
Smith
George Davey
GD
Starr
John M
JM
Hole
David J
DJ
Whalley
Lawrence J
LJ
Wilson
Valerie
V
Deary
Ian J
IJ
D000328:Adult; D000368:Aged; D002423:Cause of Death; D002648:Child; D015331:Cohort Studies; D003625:Data Collection; D005260:Female; D005541:Forced Expiratory Volume; D006306:Health Surveys; D006801:Humans; D007360:Intelligence; D008297:Male; D008498:Medical Record Linkage; D008875:Middle Aged; D009369:Neoplasms / Q000401:mortality; D010343:Patient Admission / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012606:Scotland; D012907:Smoking / Q000009:adverse effects*; D012923:Social Class; D012932:Social Facilitation