All-cause mortality in the Aberdeen 1921 birth cohort: effects of socio-demographic, physical and cognitive factors.

BACKGROUND

Childhood intelligence predicts mortality throughout most of the life span. However, it is unknown whether its effect persists into advanced old age.

METHODS

The Aberdeen Birth Cohort born in 1921 (n = 354) and that had an IQ test as part of the national Scottish Mental Survey of 1932 were seen in 1997 at age 76 years when childhood and adult socio-environmental, medical and cognitive data were collected. Participants were followed until May 2007 and vital status determined from the General Register for Scotland records. Univariate associations between baseline variables and mortality were determined and multivariable survival analysis performed with Cox's proportional hazards modelling.

RESULTS

One hundred and fifty-eight (44.6%) of the 354 cohort members had died by the census date. Significantly more men (n = 102) died during follow-up than women (n = 56, chi2 = 5.27, p = .022). Lower scores on four of the six cognitive tests at age 76 years were associated with increased mortality, but not IQ age 11. Survival was associated with gender (H.R. 0.32, 95% C.I. 0.11-0.89 for women versus men), peak expiratory flow rate (H.R. 0.997, 95% C.I. 0.992-1.001 per l/min) and the Uses of Common Objects test (H.R. 0.91, 95% C.I. 0.82-1.01)

CONCLUSION

Both physical and psychological variables independently predicted survival in old age: respiratory function and executive function in particular. Male gender conferred increased risk of mortality and this was not explained by the broad range of socio-environmental, mental ability and health status variables examined in the study.