Longitudinal Effects Of Age Research Articles

Differential trajectories of age-related changes in components of executive and memory processes.

Several studies have demonstrated age-related declines in general executive function and memory. In this study, we examined cross-sectional and longitudinal age effects in more specific cognitive processes that constitute executive function and memory. We postulated that, whereas some components of executive and memory functions would show age differences and longitudinal declines, other specific abilities would be maintained or even improve with repeated testing. In a sample of individuals ≥55 years old from the Baltimore Longitudinal Study of Aging, we found longitudinal declines in inhibition, manipulation, semantic retrieval, phonological retrieval, switching, and long-term memory over a maximum of 14 years follow-up. In contrast, abstraction, capacity, chunking, discrimination, and short-term memory were maintained or even improved longitudinally, probably due in part to repeated testing. Moreover, whereas several different abilities were correlated across participants' cross-sectional performance, longitudinal changes in performance showed more heterogeneous trajectories. Finally, compared with cross-sectional performance, longitudinal trajectories showed better distinction between participants with and those without later cognitive impairment. These results show that longitudinal cognitive aging of executive and memory functions is not a uniform process but a heterogeneous one and suggest that certain executive and memory functions remain stable despite age-related declines in other component processes.

Cerebrovascular risk factors and preclinical memory decline in healthy APOE ε4 homozygotes

To characterize the effects of cerebrovascular (CV) risk factors on preclinical memory decline in cognitively normal individuals at 3 levels of genetic risk for Alzheimer disease (AD) based on APOE genotype. We performed longitudinal neuropsychological testing on an APOE ε4 enriched cohort, ages 21-97. The long-term memory (LTM) score of the Auditory Verbal Learning Test (AVLT) was the primary outcome measure. Any of 4 CV risk factors (CVany), including hypercholesterolemia (CHOL), prior cigarette use (CIG), diabetes mellitus (DM), and hypertension (HTN), was treated as a dichotomized variable. We estimated the longitudinal effect of age using statistical models that simultaneously modeled the cross-sectional and longitudinal effects of age on AVLT LTM by APOE genotype, CVany, and the interaction between the two. A total of 74 APOE ε4 homozygotes (HMZ), 239 ε4 heterozygotes (HTZ), and 494 ε4 noncarriers were included. APOE ε4 carrier status showed a significant quadratic effect with age-related LTM decline in all models as previously reported. CVany was associated with further longitudinal AVLT LTM decline in APOE ε4 carriers (p=0.02), but had no effect in noncarriers. When ε4 HTZ and HMZ were considered separately, there was a striking effect in HMZ (p<0.001) but not in HTZ. In exploratory analyses, significant deleterious effects were found for CIG (p=0.001), DM (p=0.03), and HTN (p=0.05) in APOE ε4 carriers only that remained significant only for CIG after correction for multiple comparisons. CV risk factors influence age-related memory decline in APOE ε4 HMZ.

On the confounds among retest gains and age-cohort differences in the estimation of within-person change in longitudinal studies: A simulation study.

Although longitudinal designs are the only way in which age changes can be directly observed, a recurrent criticism involves to what extent retest effects may downwardly bias estimates of true age-related cognitive change. Considerable attention has been given to the problem of retest effects within mixed effects models that include separate parameters for longitudinal change over time (usually specified as a function of age) and for the impact of retest (specified as a function of number of exposures). Because time (i.e., intervals between assessment) and number of exposures are highly correlated (and are perfectly correlated in equal interval designs) in most longitudinal studies, the separation of effects of within-person change from effects of retest gains is only possible given certain assumptions (e.g., age convergence). To the extent that cross-sectional and longitudinal effects of age differ, obtained estimates of aging and retest may not be informative. The current simulation study investigated the recovery of within-person change (i.e., aging) and retest effects from repeated cognitive testing as a function of number of waves, age range at baseline, and size and direction of age-cohort differences on the intercept and age slope in age-based models of change. Significant bias and Type I error rates in the estimated effects of retest were observed when these convergence assumptions were not met. These simulation results suggest that retest effects may not be distinguishable from effects of aging-related change and age-cohort differences in typical long-term traditional longitudinal designs.

Cross-sectional and Longitudinal Effects of Aging for the Secondary Conditions of Spinal Cord Injury

Purpose: This study evaluates the effects of aging and years post injury (YPI) of secondary conditions common in spinal cord injury (SCI). Method: Aging and YPI are parameterized into cross-sectional and longitudinal components to determine whether changes in a particular secondary condition over time are longitudinal in nature or could be modeled using a cross-sectional design. The study also evaluates whether changes in secondary conditions are more attributable to age or YPI and whether the relationship of age and YPI with the outcome is linear or nonlinear. Results: The longitudinal component of aging was the most associated with secondary conditions, indicating that regardless of age or YPI the risk of the secondary condition changed over time. For some conditions, the direction of change for the longitudinal components and crosssectional components was in the same direction, whereas for other conditions the cross-sectional effect was in the opposite direction of the longitudinal effect. Similarly some of the secondary conditions were more associated with cross-sectional age, whereas others were more associated with cross-sectional YPI. Examples of secondary conditions that have a nonlinear association with age and YPI are provided. Conclusion: The findings of this study suggest that longitudinal study designs are warranted as the crosssectional effects were not able to detect the effects of aging in predicting the risk of secondary conditions in SCI.

Cross-sectional and Longitudinal Effects of Aging for the Secondary Conditions of Spinal Cord Injury

Cross-sectional and Longitudinal Effects of Aging for the Secondary Conditions of Spinal Cord Injury

Cross-sectional and Longitudinal Analyses of Anatomical Sulcal Changes Associated with Aging

Imaging studies of the human brain indicate that the cortex undergoes anatomic changes during the aging process. With the ability to study the human brain in vivo using magnetic resonance imaging, understanding the nature and location of these changes is of increasing interest. In this work, we investigate cross-sectional and longitudinal age effects on the geometric shape and gray matter (GM) volume for regions of interest on the cortical surface. Each of the regions corresponds to the buried cortex surrounding the sulcal spaces and is termed a "sulcal region." The study consists of 35 older adults scanned three times over a 4-year time span. The group includes 19 women and 16 men ranging in ages from 59 to 84 years (mean 70.9, standard deviation 6.2). We analyze 8 sulcal regions-the buried cortex surrounding the left and right central, superior frontal, cingulate, and parietooccipital sulci. We examine surface area, GM thickness, GM volume, sulcal depth, local gyrification index, and measures of curvature. Results indicate cross-sectional age effects in mean thickness, GM volume, sulcal depth, and curvature characteristics of sulcal regions. In addition, we found longitudinal decreases in surface area, mean thickness, GM volume, and sulcal depth measures as well as changes in sulcal curvature.

A longitudinal study of confrontation naming in the “normal” elderly

The longitudinal effects of age on confrontation naming using the 60-item Boston Naming Test (BNT) were studied in 541 "normal" elderly (ages 50-99). For participants with at least 4 annual assessments (n = 238), 150 were followed for > or =6 years, 81 for > or =8 years, and 43 for > or =10 years. A small practice effect (0.21 words, p = 0.06) and moderately high test-retest reliability were found when comparing the first 2 assessments, which were 9-15 months apart (r = 0.76, n = 353). Reliable change index scores indicated that an annual decline of > or =4 points on the BNT is needed for a statistically reliable decline in an individual. A gradient in the mean annual rate of change on the BNT was found with improvement in the 50s age group, no change in the 60s age group, and decline in the 70s and 80s age groups. When projected over 10 years, the magnitudes of the mean changes were relatively small, that is, a 1-word improvement for participants in their 50s and a 1.3-word decline for participants in their 70s. These findings demonstrate that lexical retrieval as measured by a visual object confrontation naming task is generally well preserved in aging with only subtle decline in the 7th and 8th decades of age.

Longitudinal Effects of Age at Onset and First Drinking Situations on Problem Drinking

The purpose of this study was to describe aspects of the first alcohol-use experience, and examine the predictive relations among age of first use, context of alcohol use initiation, and problem drinking with and without controls for psychosocial risk factors. Data were from the Rutgers Health and Human Development Project, a five-wave, prospective study of substance-use behaviors in a community sample. Respondents, who were first interviewed at age 12 (1979–81) and most recently at age 30 or 31 (1999–2000) (N = 371), reported on their first drinking experience, and on a range of known risk factors for alcohol abuse. Most alcohol initiation occurred during a family gathering. Regardless of initiation context, youth who drank at an early age were more likely than youth who initiated later to become problem drinkers, although the risk was relatively greater for the youth who first drank outside a family gathering. Based on multivariate logistic regressions, feeling drunk at initiation was the only onset-related variable significantly associated with problem drinking; other significant risks factors included male gender, delinquency, and family history of alcoholism. Because most initiation occurs at a family gathering, alcoholism prevention research may benefit from examining the role that drinking in family contexts could play with regard to socializing young drinkers to less risky drinking behaviors in adulthood. In particular, further research focusing on the subjective effects experienced by youth when they first drink may be merited.

Degenerative age changes in white matter connectivity visualized in vivo using magnetic resonance imaging.

Age effects on the signal characteristics of white matter (WM) were examined via magnetic resonance imaging (MRI). Global and local patterns of WM degeneration were demonstrated using a new image analysis methodology. Significant cross-sectional and longitudinal age effects were found in the WM, primarily in the left hemisphere. Importantly, signal changes, which likely reflect WM demyelination, and changes in water, protein and mineral content of tissue, were unrelated to volumetric changes. Thus, measures of tissue characteristics provide unique and complementary information to widely used measures of brain atrophy. Moreover, signal measurements displayed stronger associations with age and can potentially be more sensitive than volumetric measures as indicators of preclinical disease, because they reflect changes in the underlying tissue composition. To our knowledge, our study is the first documentation of longitudinal age- and region-dependent changes in magnetic resonance signal characteristics of WM fibers, reflecting underlying degenerative effects of aging.

Longitudinal effects of aging on serum total and free testosterone levels in healthy men. Baltimore Longitudinal Study of Aging.

Many studies have shown cross-sectional (and two small studies, longitudinal) declines in total and/or free testosterone (T) levels, with age, in men. The extent to which decline in T is the result of the aging process per se, as opposed to chronic illness, medication use, and other age-related factors, remains controversial. The frequency with which aging leads to T levels consistent with hypogonadism has also not been defined. These issues bear on the potential use of T replacement in aging men, because aging and hypogonadism have, in common, reduced bone and lean body mass and muscle strength and increased total and abdominal fat. We measured T and sex hormone-binding globulin (SHBG), by RIA, in stored samples from 890 men in the Baltimore Longitudinal Study on Aging. Using a mixed-effects model, we found independent effects of age and date of sampling to reduce T levels. After compensating for date effects, which investigation suggested was artifactual, we observed significant, independent, age-invariant, longitudinal effects of age on both T and free T index (free T index = T/SHBG), with an average change of -0.124 nmol/L.yr and -0.0049 nmol T/nmol SHBG.yr. T, but not free T index, also decreased with increasing body mass index. Use of beta-blocking drugs was associated with higher T and higher free T index levels. Using total T criteria, incidence of hypogonadal T levels increased to about 20% of men over 60, 30% over 70 and 50% over 80 yr of age, and even greater percentages when free T index criteria were employed. Our observations of health factor independent, age-related longitudinal decreases in T and free T, resulting in a high frequency of hypogonadal values, suggest that further investigation of T replacement in aged men, perhaps targeted to those with the lowest serum T concentrations, are justified.

Longitudinal Effects of Aging on Serum Total and Free Testosterone Levels in Healthy Men

Longitudinal Effects of Aging on Serum Total and Free Testosterone Levels in Healthy Men

Cross-sectional and longitudinal relationships among age, cognition, and processing speed.

Cross-sectional and longitudinal age effects on cognitive function were examined in 302 older adults followed longitudinally. Processing speed was related to cognitive performance at cross-section, and change in speed predicted within-person longitudinal cognitive decline. Statistical control of processing speed greatly reduced cross-sectional age effects but did not attenuate longitudinal aging effects. This difference in processing speed's ability to account for cross-sectional and longitudinal age effects is discussed in the context of theories of cognitive aging and methodological and statistical issues pertaining to the cross-sectional and longitudinal study of cognitive aging.

Age, period, and cohort effects on pulmonary function in a 24-year longitudinal study.

This paper proposes the use of two-factor models (age-period and age-cohort models) to estimate age, period, and cohort effects on pulmonary function by using the data collected in a 24-year longitudinal study in the Netherlands from 1965 to 1990. The analysis included 18,363 pulmonary function measurements on 6,148 subjects aged 20-54 years at the initial visit. The subjects were grouped into four birth cohorts (before 1923, 1923-1934, 1935-1946, and after 1946) and four survey periods (1965-1972, 1973-1978, 1979-1984, and 1985-1990). In the age-cohort model, the decrement in forced expiratory volume in 1 second (FEV1) associated with a yearly increase in age was 28.3 +/- 3.7 ml/year for a man 176 cm tall and 16.0 +/- 1.9 ml/year for a woman 163 cm tall. The estimated acceleration of decline with aging was significant for both men (beta = -0.212; standard error = 0.079 ml) and women (beta = -0.346; standard error = 0.058 ml). Compared with that of the cohort born before 1923, the average level of FEV1 was estimated to increase by 156, 277, and 379 ml, respectively, for the three younger cohorts in men (p = 0.01) and by 133, 213, and 328 ml for the three younger cohorts in women (p < 0.01). In the age-period model, the estimated linear age effect on FEV1 was 36.2 +/- 4.2 ml/year for a man and 30.5 +/- 2.3 ml/year for a woman. The age quadratic term was significant for women, but not for men. Average FEV1 was estimated to be increased by 141, 169, and 250 ml, respectively, for the periods 1973-1978, 1979-1984, and 1985-1990 in men and by 131, 138, and 219 ml in women. These period effects were significant for both men and women. In summary, this study applied the two-factor models to estimate cross-sectional and longitudinal effects of aging on FEV1 and demonstrated significant period and cohort effects, which could be attributed in part to changes in air pollutants, respiratory infections, vaccinations, types of cigarettes, diet, and lifestyles over time.

Age and Aerobic Power in Women: A Longitudinal Study

Thirty-six women from an original cross-sectional population of 81 were retested after an average time span of 6.1 years to determine the longitudinal effects of aging on aerobic power. Women in their 20s maintained a constant level of VO2max. All other age groups showed a decrease in aerobic power (l . min-1 and ml . kg-1 . min-1) similar to that observed in the cross-sectional study. Although the decline in VO2max was similar for both groups, active women increased walk time on the treadmill, while sedentary women decreased in endurance time. Maximal heart rate also decreased with age but the rate of decrease was not constant across time. HRmax remained relatively steady during the middle years and then declined at a faster rate in the 50- and 60-year-old age groups. The results of the present study suggest that cross-sectional studies can provide valid information about the effect of age on response to maximal exercise provided that close attention is paid to the limitations underlying regression therapy. The data also indicate a need to consider alternatives to linear regression analysis of aging effects, since the rate of change of some variables is not constant across age.