Childhood mental ability and smoking cessation in adulthood: prospective observational study linking the Scottish Mental Survey 1932 and the Midspan studies

The social and smoking data were from two of the Midspan prospective cohort studies conducted in the 1970s—the Collaborative study and the Renfrew/Paisley study. Participants completed a questionnaire and attended a physical examination. Occupational social class was coded according to the registrar general’s classification. The home address of the participants at the time of screening was retrospectively postcoded to allow deprivation category as defined by Carstairs and Morris to be ascertained. This is an area based measure obtained from four census variables—male unemployment, overcrowding, car ownership, and the proportion of heads of households in social classes IV and V. Deprivation scores were converted to seven categories ranging from 1 (least deprived) to 7 (most deprived). Participants were classified as never, past, or current smokers at midlife. Past smokers were former smokers of one year or more. Twelve pipe or cigar only smokers were excluded. Age at starting smoking was recorded for current cigarette smokers and past smokers. Data on childhood mental ability were obtained from the Scottish Mental Survey 1932 (SMS1932). The SMS1932 tested mental ability, using the Moray House Test (MHT), in almost all children born in 1921 attending school in Scotland on the 1 June 1932 (n=87 498). The MHT scores were corrected for age at testing and converted to IQ type scores (mean 100; SD 15).5 Ethical permission to link the Midspan and SMS1932 studies was obtained from the Multi-Centre Research Ethics Committee for Scotland. We successfully matched 938 (75%) participants from the Midspan studies to their MHT score at age 11.5 The proportion of never, past, and current smokers was similar between those participants who were matched and not matched to their MHT score