Cognitive reserve and mortality in dementia: the role of cognition, functional ability and depression

OBJECTIVE: This study examined whether dementia patients with greater cognitive reserve had increased mortality rates, and whether this association was different across strata of cognition, functional ability and depression. METHODS: In the community-based Amsterdam Study of the Elderly, 261 non-institutionalized dementia patients, identified using the Geriatric Mental State Schedule (GMS), were followed for an average of 55.5 months after which mortality data were obtained. Cognitive reserve was indicated by years of education and pre-morbid intelligence (measured using the Dutch Adult Reading Test). Cognition, functional ability and depression were indicated by Mini-Mental State scores, ADL and IADL measurements and GMS depressive syndrome, respectively. RESULTS: During the follow-up 146 persons (55.9%) died. Cox regression analyses showed that more highly educated dementia patients had higher mortality rates, only if they had low MMSE scores or if they had a concurrent depression. Pre-morbid intelligence was associated with a higher mortality rate, independent of cognition, but this association was much stronger among patients with depression. The positive association between education or intelligence and mortality was not modified by functional disabilities. CONCLUSIONS: The results suggest that dementia patients with greater cognitive reserve have increased mortality rates, only if the disease has progressed to such an extent that clinical symptoms are more severe. In this respect, the reserve hypothesis needs a modification. Depression in dementia patients with greater cognitive reserve may reflect a subgroup of patients with poor prognosis.     

Survival and developmental disability in infants with birth weights of 501 to 800 grams, born between 1979 and 1994

OBJECTIVE: Because the survival rate has increased for extremely low birth weight neonates, many have raised the concern that the rate of developmental disability among survivors will also increase. To address this concern, we analyzed changes over time in survival and major neurosensory impairment in a sample of extremely low birth weight infants born between July 1, 1979, and June 30, 1994. METHODS: The study sample included 513 infants with birth weights of 501 to 800 g who were cared for in either of the two neonatal intensive care units that serve a 17-county region in northwest North Carolina and who were born to mothers residing in that region. At 1 year of age (corrected for gestation), survivors were examined by a pediatrician and were tested using the Bayley Scales of Infant Development. Major neurosensory impairment was defined as cerebral palsy, a Bayley Mental Developmental Index <68, or blindness. A total of 209/216 (97%) of survivors were examined at 1 year of age. Epoch of birth was defined as follows: epoch 1, July 1, 1979 to June 30, 1984; epoch 2, July 1, 1984 to June 30, 1989; and epoch 3, July 1, 1989 to June 30, 1994. RESULTS: Survival rates for epochs 1, 2, and 3 were, respectively, 24/120 (20%), 63/175 (36%), and 129/218 (59%). In contrast, the proportions with a major neurosensory impairment did not increase over time; rates for successive epochs were 6/24 (25%), 17/61 (28%), and 26/124 (21%). Rates of cerebral palsy were 3/24 (13%), 12/61 (20%), and 9/124 (7%); rates of delayed mental development were 4/24 (17%), 12/61 (20%), and 17/124 (14%); and rates of blindness were 2/24 (8%), 0/62, and 5/124 (4%), respectively. CONCLUSIONS: This analysis suggests that the increasing survival of extremely low birth weight neonates since the late 1970s has not resulted in an increased rate of major developmental problems identifiable at 1 year of age.     

妥卡尼对豚鼠心室肌细胞钙电流和钾电流的抑制作用

利用酶分散的成年豚鼠心室肌细胞和全细胞电压钳技术,研究了妥卡尼(tocainide)对心室肌细胞钙电流(I_ca)、延迟整流钾电流(I_k)和ATP敏感性钾电流(Ik,ATP)的作用。结果表明,妥卡尼对I_ca和I_k均显示浓度相关的抑制作用,妥卡尼50umol·L^-1对I_ca和I_k的抑制率分别为16%和3%。这可能是妥卡尼有效抑制室上性心动过速和缩短心肌动作电位平台期的重要机制。     

Measures of physical performance and risk for progressive and catastrophic disability: results from the Women's Health and Aging Study

BACKGROUND: Physical performance measures can predict incident disability, but little research has assessed and compared how these measures predict progressive and rapid-onset (catastrophic) disability. The authors evaluated the ability of upper and lower extremity performance measures to predict progressive and catastrophic disability in activities of daily living (ADL), mobility, and upper extremity function. METHODS: The incidence of progressive and catastrophic disability was assessed semiannually during a 3-year period in 884 women participating in the Women's Health and Aging Study I. Four-meter walking speed, balance, and chair stands tests were used to evaluate lower extremity function. The putting-on-blouse test, the Purdue pegboard test, and grip strength were used to assess upper extremity function. Summary performance scores (SPS) for the lower and upper extremities were calculated. Among participants in whom disability developed, those who reported no difficulty in the previous year were defined as cases of catastrophic disability, and those who previously reported little or some difficulty were considered to be cases of progressive disability. Cox proportional hazard regression analyses were used to evaluate the association of performance measures and time to incident disability. The predictive ability of performance measures was compared using receiver-operator characteristic curves. RESULTS: All lower and upper extremity measures, with the exception of grip strength, significantly predicted the onset of progressive ADL disability, but only walking speed was significantly associated with the onset of catastrophic ADL disability. The chair stands test, walking speed, and the lower extremity SPS were significantly associated with the onset of both progressive and catastrophic mobility disability. Only lower extremity individual tests and SPS significantly predicted the onset of both progressive and catastrophic upper extremity disability. The receiver-operator characteristic curves for ADL and mobility disability showed that all performance measures evaluated had a greater predictive ability for progressive than for catastrophic incident disability. This finding was not consistent for upper extremity disability. The areas under the curve for walking speed and lower extremity SPS were very similar, ranging from 0.58 to 0.81 and from 0.57 to 0.85, and the predictive ability of these two measures was the greatest for all disability outcomes assessed. CONCLUSION: Physical performance measures of lower extremity and, in particular, walking speed and lower extremity SPS are valuable tools to predict different forms of disability, especially those with a progressive onset.     

Brief Report: Educational attainment does not influence brain aging

Education has been related to various advantageous lifetime outcomes. Here, using longitudinal structural MRI data (4,422 observations), we tested the influential hypothesis that higher education translates into slower rates of brain aging. Cross-sectionally, education was modestly associated with regional cortical volume. However, despite marked mean atrophy in the cortex and hippocampus, education did not influence rates of change. The results were replicated across two independent samples. Our findings challenge the view that higher education slows brain aging.