Cognitive ability in childhood and cognitive decline in mid-life: longitudinal birth cohort study
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《英国医生杂志》
1 MRC National Survey of Health and Development, Department of Epidemiology and Public Health, University College London, London WC1E 6BT, 2 Department of Epidemiology and Public Health, University College London, 3 Department of Epidemiology, Biostatistics and Occupational Health, McGill University Faculty of Medicine, 1020 Pine Avenue West Montreal QC, Canada H3A 1A2
Correspondence to: M Richards m.richards@ucl.ac.uk
Abstract
Cognitive decline is associated with functional impairment1 and is a risk factor for frank dementia.2 Considerable effort has therefore been invested in identifying its causes. While sociodemographic factors have been examined,3 much less is known about the lifetime influence of cognitive ability. Lower ability in childhood4 and early adulthood5 is associated with increased risk of dementia, but the influence of early ability on general cognitive decline is less understood. A recent study found no difference in rate of cognitive change throughout life according to estimated level of early ability.6 Using data from the British birth cohort we investigated the association between measured ability in childhood and rate of decline in memory, speed, and concentration in mid-life, controlling for educational and occupational attainment. Because cohort members had been administered the national adult reading test (NART) at the age of 53 years we were also able to investigate possible independent effects of ability in childhood and adulthood on rate of decline in these measures.
Methods
Missing data
Of the 3035 cohort members interviewed at 53 years, 2058 (1004 men and 1054 women) had complete data for ability at 15 years, educational attainment, adult social class, memory and search speed at 43 and 53 years, and the adult reading test score at 53 years. Those with missing data for any of these variables had lower ability scores at the age of 15 than those with complete information (P < 0.001). Table 1 shows means and frequency distributions for these variables, separately for males and females.
Table 1 Unadjusted means (SD) for cognitive test scores and frequency distributions (number (percentage)) for educational attainment and occupational social class
Childhood ability and decline in memory
Table 2 shows regression coefficients () for the association between AH4 score at the age of 15 and decline in memory from 43 to 53 years. Positive coefficients indicate that higher AH4 scores were associated with slower decline in memory in men and women (model 1). The magnitude of this association was reduced after we adjusted for education and social class (model 2) and reduced further after additional adjustment for the reading test score at 53 years (model 3), although the AH4 remained independently associated with decline below the 1% significance level after all these adjustments.
Table 2 Regression coefficients (95% confidence intervals) representing rate of decline in memory per unit increase in AH4 ability score at age 15. Positive coefficients indicate slower decline
We saw a similar pattern when we repeated these analyses using Watts-Vernon comprehension instead of the AH4 (data not shown), with higher score associated with slower decline in memory after we adjusted for education, social class, and the reading test score in men (regression coefficient 0.12, 95% confidence interval 0.05 to 0.19, P < 0.001) and women (0.10, 0.04 to 0.17, P = 0.003).
Childhood ability and decline in search speed
Table 3 shows regression coefficients for the association between AH4 score at the age of 15 and decline in search speed from 43 to 53 years. Again, higher AH4 scores were associated with slower decline in speed in men and women (model 1), although adjustment for education and social class (model 2) had less of an attenuating effect than it did on the association between AH4 and memory. For men this was also true when we additionally adjusted for the reading test (model 3), although it attenuated the effect for women.
Table 3 Regression coefficients (95% confidence intervals) representing rate of decline in visual search speed per unit increase in AH4 ability score at age 15. Positive coefficients indicate slower decline
For men, Watts-Vernon comprehension was not associated with decline in search speed after we adjusted for education and social class (0.00, -0.07 to 0.06, P = 0.93). For women this score remained significantly associated with decline in search speed after adjustment (0.09, 0.02 to 0.16, P = 0.01), although this was no longer the case after we additionally adjusted for the adult reading test score (0.03, -0.06 to 0.11, P = 0.52).
Adult ability and cognitive decline
Correlations between the AH4 and adult reading test score were 0.59 for men and 0.55 for women. For men and women higher adult reading test scores were associated with slower decline in memory, independent of the AH4 (table 2). These associations were also independent of Watts-Vernon comprehension (data not shown) and of similar magnitude. In women only the adult reading test score was inversely associated with decline in speed (P = 0.008, table 3). This was also the case when we substituted the Watts-Vernon score for the AH4 score. Overall, a 10 point decrease in raw adult reading test score corresponded to 1.4 word increase in memory decline, after we controlled for AH4, education, and occupation, and a 2.1 letter increase in search speed decline. Figures for the AH4 itself were 0.3 and 4.2, respectively. AH4 and reading test scores together accounted for 3% of the variance for memory decline and 1% of the variance for search speed decline, after we controlled for education and occupation.
Education, social class, and health
Increasing educational attainment was associated with slower decline in memory in men and women, independent of ability in childhood (model 2). These associations were attenuated when we adjusted for the reading test score (model 3), particularly in men. Occupational social class had a negligible independent effect on memory decline (see table 2).
There was no independent association between education and decline in search speed (table 3). This was also the case for social class, although in men there was a trend for slower decline with higher occupational attainment.
Coefficients representing associations between ability and decline were not significantly altered when we adjusted, in turn, for smoking, alcohol consumption, affective state, body mass index, exercise, pulse, blood pressure, and forced expiratory volume in one second at 43 or 53 years.
Discussion
Moritz DJ, Kasl SV, Berkman LF. Cognitive functioning and the incidence of limitations in activities of daily living in an elderly community sample. Am J Epidemiol 1995;141: 41-9.
Brayne C, Best N, Muir M, Richards SJ, Gill C. Five-year incidence and prediction of dementia and cognitive decline in a population sample of women aged 70-79 at baseline. Int J Geriatr Psychiatry 1997;12: 1107-18.
Lee S, Kawachi I, Berkman LF, Grodstein F. Education, other sociodemographic indicators, and cognitive decline. Am J Epidemiol 2003;157: 712-20.
Whalley LJ, Deary IJ. Longitudinal cohort study of childhood IQ and survival up to age 76. BMJ 2001;322; 819-22.
Snowdon DA, Kemper SJ, Mortimer JA, Greinier LH, Wekstein DR, Markesbery WR. Linguistic ability in early life and cognitive function and Alzheimer's disease in later life: findings from the nun study. JAMA 1996;21: 528-32.
Rabbitt P, Chetwynd A, McInnes L. Do clever brains age more slowly? Further exploration of a nun result. Br J Psychol 2003;94: 63-71.
Wadsworth MEJ. The imprint of time: childhood, history and adult life. Oxford: Clarendon Press, 1991.
Wadsworth MEJ, Butterworth SL, Hardy R, Kuh D, Richards M, Langenberg C, Connor M. The life course design: an example of benefits and problems associated with study longevity. Soc Sci Med (in press).
Heim AW. The AH4 group test of intelligence. Windsor: NFER-Nelson, 1970.
Pigeon DA. Details of the fifteen years tests. In: Douglas JWB, Ross JM, Simpson HR, eds. All our future. London: Davies, 1968.
Nelson HE, Willison JR. National adult reading test (NART). 2nd ed. Windsor: NFER-Nelson, 1991.
Deary IJ, MacLennan WJ, Starr JM. Is age kinder to the initially more able?: differential ageing of a verbal ability in the healthy old people in Edinburgh study. Intelligence 1999;26: 357-75.
Richards M, Hardy R, Wadsworth MEJ. Does active leisure protect cognition? Evidence from a national birth cohort. Soc Sci Med 2003:56: 785-92.
Richards M, Jarvis MJ, Thompson N, Wadsworth MEJ. Cigarette smoking and cognitive decline in midlife: evidence from a prospective birth cohort study. Am J Public Health 2003;93: 994-98.
Salthouse TA. The processing speed theory of adult age differences in cognition. Psychol Rev 1996;103: 403-28.
Plomin R. Genetics and general cognitive ability. Nature 1999;402 (6761 suppl): C25-9.
Berger A. Insulin-like growth factor and cognitive function. BMJ 2001;322: 203.
Wellberg LAM, Seckle JR. Prenatal stress, glucocorticoids and the programming of the brain. J Neuroendocrinol 2001;13: 113-28.
Douglas JWB. The home and the school. London: MacGibbon & Kee, 1964.
Rutter M. Family and school influences on cognitive development. J Child Psychol Psychiatry 1995;26: 683-704.
Schmand B, Smit JH, Geelings, Lindeboom J. The effect of intelligence and education on the development of dementia. Psychol Med 1997;27: 1337-44.
Rabbitt P. Does it all go together when it goes? Q J Exp Psychol 1993;46(A): 385-433.(Marcus Richards, MRC scie)
Correspondence to: M Richards m.richards@ucl.ac.uk
Abstract
Cognitive decline is associated with functional impairment1 and is a risk factor for frank dementia.2 Considerable effort has therefore been invested in identifying its causes. While sociodemographic factors have been examined,3 much less is known about the lifetime influence of cognitive ability. Lower ability in childhood4 and early adulthood5 is associated with increased risk of dementia, but the influence of early ability on general cognitive decline is less understood. A recent study found no difference in rate of cognitive change throughout life according to estimated level of early ability.6 Using data from the British birth cohort we investigated the association between measured ability in childhood and rate of decline in memory, speed, and concentration in mid-life, controlling for educational and occupational attainment. Because cohort members had been administered the national adult reading test (NART) at the age of 53 years we were also able to investigate possible independent effects of ability in childhood and adulthood on rate of decline in these measures.
Methods
Missing data
Of the 3035 cohort members interviewed at 53 years, 2058 (1004 men and 1054 women) had complete data for ability at 15 years, educational attainment, adult social class, memory and search speed at 43 and 53 years, and the adult reading test score at 53 years. Those with missing data for any of these variables had lower ability scores at the age of 15 than those with complete information (P < 0.001). Table 1 shows means and frequency distributions for these variables, separately for males and females.
Table 1 Unadjusted means (SD) for cognitive test scores and frequency distributions (number (percentage)) for educational attainment and occupational social class
Childhood ability and decline in memory
Table 2 shows regression coefficients () for the association between AH4 score at the age of 15 and decline in memory from 43 to 53 years. Positive coefficients indicate that higher AH4 scores were associated with slower decline in memory in men and women (model 1). The magnitude of this association was reduced after we adjusted for education and social class (model 2) and reduced further after additional adjustment for the reading test score at 53 years (model 3), although the AH4 remained independently associated with decline below the 1% significance level after all these adjustments.
Table 2 Regression coefficients (95% confidence intervals) representing rate of decline in memory per unit increase in AH4 ability score at age 15. Positive coefficients indicate slower decline
We saw a similar pattern when we repeated these analyses using Watts-Vernon comprehension instead of the AH4 (data not shown), with higher score associated with slower decline in memory after we adjusted for education, social class, and the reading test score in men (regression coefficient 0.12, 95% confidence interval 0.05 to 0.19, P < 0.001) and women (0.10, 0.04 to 0.17, P = 0.003).
Childhood ability and decline in search speed
Table 3 shows regression coefficients for the association between AH4 score at the age of 15 and decline in search speed from 43 to 53 years. Again, higher AH4 scores were associated with slower decline in speed in men and women (model 1), although adjustment for education and social class (model 2) had less of an attenuating effect than it did on the association between AH4 and memory. For men this was also true when we additionally adjusted for the reading test (model 3), although it attenuated the effect for women.
Table 3 Regression coefficients (95% confidence intervals) representing rate of decline in visual search speed per unit increase in AH4 ability score at age 15. Positive coefficients indicate slower decline
For men, Watts-Vernon comprehension was not associated with decline in search speed after we adjusted for education and social class (0.00, -0.07 to 0.06, P = 0.93). For women this score remained significantly associated with decline in search speed after adjustment (0.09, 0.02 to 0.16, P = 0.01), although this was no longer the case after we additionally adjusted for the adult reading test score (0.03, -0.06 to 0.11, P = 0.52).
Adult ability and cognitive decline
Correlations between the AH4 and adult reading test score were 0.59 for men and 0.55 for women. For men and women higher adult reading test scores were associated with slower decline in memory, independent of the AH4 (table 2). These associations were also independent of Watts-Vernon comprehension (data not shown) and of similar magnitude. In women only the adult reading test score was inversely associated with decline in speed (P = 0.008, table 3). This was also the case when we substituted the Watts-Vernon score for the AH4 score. Overall, a 10 point decrease in raw adult reading test score corresponded to 1.4 word increase in memory decline, after we controlled for AH4, education, and occupation, and a 2.1 letter increase in search speed decline. Figures for the AH4 itself were 0.3 and 4.2, respectively. AH4 and reading test scores together accounted for 3% of the variance for memory decline and 1% of the variance for search speed decline, after we controlled for education and occupation.
Education, social class, and health
Increasing educational attainment was associated with slower decline in memory in men and women, independent of ability in childhood (model 2). These associations were attenuated when we adjusted for the reading test score (model 3), particularly in men. Occupational social class had a negligible independent effect on memory decline (see table 2).
There was no independent association between education and decline in search speed (table 3). This was also the case for social class, although in men there was a trend for slower decline with higher occupational attainment.
Coefficients representing associations between ability and decline were not significantly altered when we adjusted, in turn, for smoking, alcohol consumption, affective state, body mass index, exercise, pulse, blood pressure, and forced expiratory volume in one second at 43 or 53 years.
Discussion
Moritz DJ, Kasl SV, Berkman LF. Cognitive functioning and the incidence of limitations in activities of daily living in an elderly community sample. Am J Epidemiol 1995;141: 41-9.
Brayne C, Best N, Muir M, Richards SJ, Gill C. Five-year incidence and prediction of dementia and cognitive decline in a population sample of women aged 70-79 at baseline. Int J Geriatr Psychiatry 1997;12: 1107-18.
Lee S, Kawachi I, Berkman LF, Grodstein F. Education, other sociodemographic indicators, and cognitive decline. Am J Epidemiol 2003;157: 712-20.
Whalley LJ, Deary IJ. Longitudinal cohort study of childhood IQ and survival up to age 76. BMJ 2001;322; 819-22.
Snowdon DA, Kemper SJ, Mortimer JA, Greinier LH, Wekstein DR, Markesbery WR. Linguistic ability in early life and cognitive function and Alzheimer's disease in later life: findings from the nun study. JAMA 1996;21: 528-32.
Rabbitt P, Chetwynd A, McInnes L. Do clever brains age more slowly? Further exploration of a nun result. Br J Psychol 2003;94: 63-71.
Wadsworth MEJ. The imprint of time: childhood, history and adult life. Oxford: Clarendon Press, 1991.
Wadsworth MEJ, Butterworth SL, Hardy R, Kuh D, Richards M, Langenberg C, Connor M. The life course design: an example of benefits and problems associated with study longevity. Soc Sci Med (in press).
Heim AW. The AH4 group test of intelligence. Windsor: NFER-Nelson, 1970.
Pigeon DA. Details of the fifteen years tests. In: Douglas JWB, Ross JM, Simpson HR, eds. All our future. London: Davies, 1968.
Nelson HE, Willison JR. National adult reading test (NART). 2nd ed. Windsor: NFER-Nelson, 1991.
Deary IJ, MacLennan WJ, Starr JM. Is age kinder to the initially more able?: differential ageing of a verbal ability in the healthy old people in Edinburgh study. Intelligence 1999;26: 357-75.
Richards M, Hardy R, Wadsworth MEJ. Does active leisure protect cognition? Evidence from a national birth cohort. Soc Sci Med 2003:56: 785-92.
Richards M, Jarvis MJ, Thompson N, Wadsworth MEJ. Cigarette smoking and cognitive decline in midlife: evidence from a prospective birth cohort study. Am J Public Health 2003;93: 994-98.
Salthouse TA. The processing speed theory of adult age differences in cognition. Psychol Rev 1996;103: 403-28.
Plomin R. Genetics and general cognitive ability. Nature 1999;402 (6761 suppl): C25-9.
Berger A. Insulin-like growth factor and cognitive function. BMJ 2001;322: 203.
Wellberg LAM, Seckle JR. Prenatal stress, glucocorticoids and the programming of the brain. J Neuroendocrinol 2001;13: 113-28.
Douglas JWB. The home and the school. London: MacGibbon & Kee, 1964.
Rutter M. Family and school influences on cognitive development. J Child Psychol Psychiatry 1995;26: 683-704.
Schmand B, Smit JH, Geelings, Lindeboom J. The effect of intelligence and education on the development of dementia. Psychol Med 1997;27: 1337-44.
Rabbitt P. Does it all go together when it goes? Q J Exp Psychol 1993;46(A): 385-433.(Marcus Richards, MRC scie)