Physical health and cognition

Introduction, This chapter deals with the impact of physical health on cognition. There are several lines of research and thinking that support the conception that physical health may be an important factor affecting cognition. One line of research is represented by the body of studies showing that good health in adulthood manifested in longer life expectancy (Deary et al., 2004; Hart et al., 2003; Kuh et al., 2003; Osler et al., 2003), low prevalence of cardio-vascular disease (Batty et al., 2005), and low incidence of serious illness, at least in the 30–39 year age group (Martin et al., 2004), is associated with good mental ability (intelligence) during childhood. Martin et al. (2004) calculated that a lower level of serious disease by a third is correlated with a 15 points higher IQ. Further correlational studies show that straightforward indicators of health in early childhood, such as birth weight and height growth, are related positively to cognitive function in childhood, adolescence, and early adulthood as well as to educational attainment (Richards et al., 2001, 2002). The impact of physical state on cognition is however not limited to childhood. Cognitive ability at 18–20 years is also related to coronary health in middle age (Hemmingsson et al., 2007). Notably, early cognitive function is a major predictor of cognitive function and its rate of change in midlife and beyond as well as of educational and occupational attainment (McCall, 1979). One explanation for these effects is that a variety of hormones target brain areas responsible for cognition at the same time they are playing a critical role in determining body size and physical health. The effect remains valid even if the explanation that hinges on the intermediation of socioeconomic factors proves to be correct (Gottfredson & Deary, 2001).