DO HEALTH BEHAVIORS AFFECT COGNITIVE CHANGE SIMILARLY ACROSS ABILITIES ?

Cognitive gain and decline, ability specific (e.g. Inductive Reasoning, Verbal Comprehension, Perceptual Speed, Spatial Orientation, Numeric Facility, Verbal Memory) and global (e.g. IQ (intelligence quotient), EQ (education quotient)), were predicted from eight health behavior domains: smoking abstention, alcohol use, food consumption, food preparation, exercise, seat belt use, dental care, and medical check-ups. 970 Seattle Longitudinal Study participants who had 1991 and 1998 cognitive test data and 1993 health behavior data were included in the current investigation. Mean age for sample was 65.39 years (Range= 29-96; SD= 14.37) and mean education was 15.43 years (Range= 7-20; SD= 2.70). To examine age group differences the sample was divided into three age groups 1) 29-54 year olds (N=244); 2) 55-67 year olds (N=237); and 3) 68-96 year olds (N=489). The statistical criterion for “gain” and “decline” was one standard error of measurement (SEM) above or below their 1991 cognitive score. Logistic regression was used to predict change in cognitive ability from the health behavior domains. After controlling for age, income, education, and simultaneously accounting for all other health behavior domains: results indicated that in the total sample, Exercise significantly predicted gain in IQ, Alcohol Consumption significantly predicted gain in EQ, Exercise significantly predicted gain in Inductive Reasoning, Food Preparation significantly predicted gain in Spatial Ability, Food Consumption, Seat Belt Use, Medical Check-ups significantly predicted decline in Spatial Ability; Medical Check-ups significantly predicted decline in Number Ability; and Food Preparation significantly predicted gain in Verbal Memory. Health behaviors did not predict gain or decline in either Verbal Ability or Perceptual Speed, gain in Number Ability, or decline in IQ and EQ Although these results imply that health behaviors do not predict cognitive change similarly across all abilities, it was shown that 7-year cognitive change can be predicted from some health behaviors assessed five year prior to cognitive follow-up. When examining age group differences, divergent patterns of health behavior predictors for cognitive change emerged, all eight health behaviors emerged as significant predictors for at least one of the age groups, implying the need to examine health behavior effects on cognitive change separately and by age groups. Predicting Cognitive Change 3 DO HEALTH BEHAVIORS AFFECT COGNITIVE CHANGE SIMILARLY ACROSS ABILITIES? Health behaviors are a vital component in explaining individual differences in physical and psychological development into old age and have been recognized as one mechanism that can influence the compression of morbidity (Fries, 1983). Health behaviors have also been recognized as one possible path involved in improving societal health conditions (U.S. Department of Health, Education, and Welfare 1979). The empirical literatures on health behaviors have shown health behavior influences on cognitive performance, mortality, and disability outcomes (Blumenthal, et. al., 1991; Hawkins & Anderson, 1996; McGinnus & Foege, 1993). The current study is focused on predicting cognitive change, using eight specific health behavior domains: smoking, alcohol, food preparation, food consumption, exercise, seat belt use, dental care, and medical check-ups. While there is research on cognitive ability and health behaviors, finding longitudinal studies examining health behavior effects on cognitive change in limited. There is a limited amount of research on general health behaviors and cognitive ability. However, within the existing literature the focus is on specific health behaviors and their association with cognitive ability. Therefore, the associations between specific health behaviors and cognitive ability will be discusses. It is important to note the directionality of the reviewed literature. Health behavior and cognitive ability research is generally represented in a uni-directional manner with the specified health behavior thought to affect cognitive performance using a cross-sectional design rather than longitudinal methods, leaving the claim of causality to be questionable (Schaie, 1996). Nevertheless, the literature reviewed below remains informative in identifying associations between specific health behaviors and cognitive ability. Smoking and Cognitive Ability Studies that have compared groups of individuals on their smoking status have shown a negative association between smoking and cognitive performance throughout most of the lifespan (Carmelli, Swan, Reed, Schellenberg, & Christian, 1999; Elmwood, Gallacher, Hopkinson, Pickering, Rabbit, Stollery, Brayne, Huppert, Bayer, 1999; Foulds, Stapleton, Bell, McSorley, & Russell, 1996). Foulds, et al., (1996) found smokers to perform cognitively worse than nonsmokers in their population of 18 to 39 year olds. The Elmwood, et al., (1999) study of men aged 55-69 found that current smokers had the lowest scores on cognitive performance relative to men who have never smoked or who were ex-smokers. Carmelli et al., (1999) also found smoking to be associated with poor cognitive performance in white male veterans aged 59 to 69 years. Alcohol and Cognitive Ability The literature on alcohol consumption and cognitive ability suggests that individuals that sustain from alcohol perform better cognitively. However, the literature also indicates that light alcohol intake may act as a protective factor for age-related change in cognitive performance. Higher levels of cognitive performance have been associated with lower levels of alcohol consumption across the adult lifespan (Christian, Reed, Caremelli, & Page, 1995; Span & Earlywine, 1999). However, there is also an apparent protective effect on cognitive performance found among middle to young-old adults, with light drinking modifying the age-related cognitive trajectory (Carmelli, et al., 1999). Alcohol has also been shown to have both long-term and short-term effects on cognitive performance. When comparing alcoholics vs. nonalcoholics, alcoholics show relatively more deficits in cognitive performance for individuals at all Predicting Cognitive Change 4 adult ages (Arbuckle, Chaikelson, & Gold, 1994; Christian et al., 1995; Hendrie, Gao, Hall, & Hui, 1996; Parsons, 1998; Nixon, 1994; Williams & Skinner, 1990). In addition, an increased consumption of alcohol over time has been associated with a decline in specific cognitive performance for middle-aged and older women (Edelstein, Kritz-Silverstein, & Barrett-Connor, 1999). Nutrition and Cognitive Ability The literature has shown that positive nutrition behaviors have a positive affect on both child and adult cognitive performance. Thatcher, McAlaster, Lester, and Cantor (1984) found a positive relationship between carbohydrate intake and reading achievement in young and adolescent children. In college-aged adults, an evening meal was found to improve performance on logical reasoning and caffeine was found to improve performance on cognitive tasks that require attention (Smith, Maben, & Brockman, 1994). Smith, Kendrick, Maben, and Salmon (1994) found that college students who ate breakfast had improved performance on free recall and memory recognition tasks but impaired accuracy on logical reasoning tasks. In the same study, caffeine intake was also found to have a positive effect on performance of semantic memory, logical reasoning, free recall, and recognition memory tasks. On the other hand, a significant reduction in food intake had a negative effect on cognitive performance in young and middleaged adults (Green, Elliman, & Rogers, 1995; Green, Elliman, & Rogers, 1997; Rogers & Green, 1993). Exercise and Cognitive Ability Physical exercise has been shown to have both a short-term and long-term positive effect on cognitive performance. Experimental studies have generally found that exercise has a beneficial shortterm effect on cognitive performance for adults throughout the lifespan (Hawkins & Anderson, 1996; Kramer, Hahn, Cohen, Banich, McAuley, Harrison, Chason, Vakil, Bardell, Boileau, & Colcombe, 1999). In addition, exercise status has also been found to predict individual cognitive performance (Lochbaum, 1999) while intensive exercise has not been found to have a negative effect on cognitive performance (Zerfaz, 1991). Exercise can intervene in the cognitive trajectory and function as a protective or modifying factor in age-related cognitive decline. Exercise has been found to positively modify age-related changes in reaction times (Emery, Huppert, & Schein, 1995). Older individuals that are fit often process cognitive information more efficiently than those that are not fit (Chodzko-Zajko, 1991). Driving Behaviors and Cognitive Ability There have not been any direct investigations of the effect of cognitive performance on seat belt use. However, the literature does provide some insight on safe driving regarding the relationship between cognitive ability and driving behaviors. Safe driving behavior is a concern for both young, inexperienced drivers and older, experienced drivers, but for varying reasons. In the young, the reason for concern can be due to a lack of experience in driving. However in older drivers, there is a concern due to age-related changes in the senses and cognitive ability (Dobbs, Heller, & Schopflocher, 1998). One study found that drivers above the age of 65 that have been involved in motor vehicle accidents perform relatively less well on tests of visuoconstructive ability (spatial), visuospatial memory (spatial memory), and psychomotor speed (speed of processing) when compared to drivers that have not have their license suspended or have not been involved in car accidents (Lundberg, Hakamies-Blomqvist, Almkvist, & Johansson (1998). The same study also indicated that an analysis of an individual’s visuoconstructive ability, visuospatial memory, and ver