Effects of cognitive impairment and loss of physical capacities on survival of the elderly

Geriatric conditions, rather than multimorbidity, as predictors of disability and mortality among octogenarians: A population-based cohort study

AIM

To examine the impact of geriatric conditions and multimorbidity on the risk of incident disability and mortality among young-old and old-old adults.

METHODS

The present study used nationally-representative data from the "Survey of Health and Living Status of the Elderly in Taiwan" for the years 2003 and 2007. Non-disabled older adults were divided into two age groups (65-79 years and ≥80 years). Chronic morbidities and geriatric conditions were assessed in 2003. Incident disability was defined as dependency in one or more activities of daily living in 2007. Vital statistics of the participants was linked to death registration data through 31 December 2007. Multivariable logistic regression and Cox regression were used to determine the effect of multimorbidity and geriatric conditions on health outcomes.

RESULTS

Among those aged 65-79 years (n = 1874), the presentation of multimorbidity or two or more geriatric conditions was related to incident disability. Among octogenarians, the presentation of one or more geriatric conditions, but not multimorbidity, was shown to be independently associated with the risk of disability. Multimorbidity was related to a higher adjusted risk of mortality in the young-old group (hazard ratio 1.54; 95% confidence interval 1.1-2.2) but not in the old-old group. Among octogenarians, those with two or more geriatric conditions had a higher adjusted risk of mortality (hazard ratio 1.7; 95% confidence interval 1.2-2.5), compared with those with 0-1 geriatric conditions.

CONCLUSIONS

The risk of incident disability and mortality increased in octogenarians with geriatric conditions, but not in cases with multimorbidity.

Sex differences in the impact of diabetes on the risk of geriatric conditions

AIM

To examine whether sex differences exist in the relationship between diabetes and geriatric conditions.

METHODS

This was a cross-sectional analysis of 2629 community-dwelling older adults, drawn from the 2003 wave of the "Survey of Health and Living Status of the Elderly in Taiwan." Selected geriatric conditions included cognitive impairment, depression, falls and urinary incontinence (UI). Diabetes and comorbid conditions (heart disease, hypertension, chronic lung disease, stroke, hip fracture, arthritis, chronic kidney disease and cancer) were assessed using questionnaires.

RESULTS

A greater proportion of older women, compared with men, had cognitive impairment (15.8% vs 7.3%), depression (22.6% vs 10.4%), falls (26.7% vs 16.3%), and UI (20.9% vs 15.1%). After adjustment for basic demographics and comorbid conditions, diabetes was associated with increased risk for cognitive impairment (RR 1.85 [CI 1.12-3.05], P=0.017), depression (RR 2.03 [CI 1.39-2.97], P=0.0003) and falls (RR 1.72 [CI 1.2-2.48], P=0.003), but not UI (RR 1.4 [CI 0.9-2.1], P=0.067) among older women. However, we did not find any associations in men.

CONCLUSIONS

Diabetes was associated with excessive risk for geriatric conditions among older women, but not men. The effect of sex differences on the relationship between diabetes and geriatric conditions requires further exploration.

Functional decline in cognitive impairment--the relationship between physical and cognitive function

BACKGROUND

Physical function decline is associated with dementia, which might either be mediated by the coexisting sarcopenia or directly related to the impaired cognition. Our objectives are to examine the relationship between cognitive function and performance-based physical function and to test the hypothesis that cognitive function is related to poor physical function independent of muscle mass.

METHODS

We measured muscle strength, performance-based physical function and muscle mass using dual-energy X-ray absorptiometry and cognitive function using the cognitive part of the Community Screening Instrument of Dementia (CSI-D) in 4,000 community-dwelling Chinese elderly aged >65 years. A CSI-D cognitive score of >28.40 was considered as cognitively impaired. The effect of cognitive impairment on muscle strength and physical function was analyzed by multivariate analysis with adjustment for age, appendicular skeletal mass (ASM), the Physical Activity Scale for the Elderly (PASE) and other comorbidities.

RESULTS

In both genders, the cognitively impaired (CSI-D cognitive score >28.40) group had a weaker grip strength (-5.10 kg, p < 0.001 in men; -1.08 kg in women, p < 0.001) and performed worse in the two physical function tests (in men, 6-meter walk speed, -0.13 m/s, p < 0.001, chair stand test, 1.42 s, p < 0.001; in women, 6-meter walk speed, -0.08 m/s, p < 0.001, chair stand test, 1.48 s, p < 0.001). After adjustment for age, ASM, PASE and other comorbidities, significant differences in grip strength (-2.60 kg, p < 0.001 in men; -0.49 kg, p = 0.011 in women) and the two physical function tests persisted between the cognitively impaired and nonimpaired group (in men, 6-meter walk speed, -0.072 m/s, p < 0.001, chair stand test, 0.80 s, p = 0.045; in women, 6-meter walk speed, -0.049 m/s, p < 0.001, chair stand test, 0.98 s, p < 0.001).

CONCLUSIONS

Poor physical function and muscle strength coexisted with cognitive impairment. This relationship was independent of muscle mass. It is likely therefore that the functional decline in dementia might be related directly to factors resulting in cognitive impairment independently of the coexisting sarcopenia.

Corpus callosum size, reaction time speed and variability in mild cognitive disorders and in a normative sample

Intra-individual variability in reaction time increases with age and with neurological disorders, but the neural correlates of this increased variability remain uncertain. We hypothesized that both faster mean reaction time (RT) and less intra-individual RT variability would be associated with larger corpus callosum (CC) size in older adults, and that these associations would be stronger in adults with mild cognitive disorders. A normative sample (n=432) and a sample with mild cognitive disorders (n=57) were compared on CC area, RT mean and RT variability adjusting for age, sex, education, APOE genotype, smoking, alcohol consumption, grip strength, visual acuity, handedness and lung function. Samples did not differ in CC area or intra-cranial volume. In the normative sample, simple RT (SRT) and choice RT (CRT) were negatively associated with CC area but there were minimal associations between CC area and intra-individual RT variability. In the mild cognitive disorders sample, SRT, CRT and intra-individual variability on the SRT task were associated with CC area. Increased RT variability explained up to 12.7 percent of the variance in CC area in the sample with mild cognitive disorders, but less than 1 percent of the variance in CC area in the normative sample. There were no associations with APOE genotype. We conclude that intra-individual variability is associated with CC area in mild cognitive disorders, but not in normal aging. We propose that biological limits on reserve capacity must occur in mild cognitive disorders that result in stronger brain-behavior relationships being observed.

Cognitive impairment and mortality among nonagenarians: the Danish 1905 cohort survey

Cognitive impairment has been associated with increased mortality. Most studies, however, have only included small numbers, if at all, of the very old. In a large nationwide survey of all Danes born in 1905 and still alive in 1998, where the baseline examination was conducted, we examined the impact of cognitive impairment on mortality over a 2-year period. No cognitive impairment was defined as a score of 24-30 points on the Mini Mental State Examination, mild cognitive impairment was defined as a score of 18-23 points, and severe impairment was defined as a score of 0-17 points. Cox regression analysis was applied to adjust for a number of known and suspected factors known or suspected of being associated with cognition and mortality (e.g. sociodemographic factors, sex, smoking, alcohol consumption, depressive symptoms, and physical abilities), and yielded hazard ratios (95% confidence interval) of 1.24 (1.00-1.55) for mildly impaired and 1.73 (1.37-2.20) for severely impaired Danes compared to individuals with no impairment. Cognitive impairment predicts mortality among the very old, even after controlling for most known predictors of mortality.

Longest held occupation in a lifetime and risk of disability in activities of daily living

OBJECTIVES

To examine the association between the longest held occupation in a lifetime and risk of disability in activities of daily living (ADL) among elderly people (65 years and older) in northern Taiwan.

METHODS

A case-control design was used nested within two cohorts of a total of 2198 elderly people who had been followed up either between 1993 and 1997 or between 1996 and 1997. Cases were 360 elderly people with ADL disability within the study period. For each case, two sex matched controls were randomly sampled from the pool of elderly people free from ADL disability. Occupational data were collected through interviews conducted in 1997. Performed job contents were classified into occupational categories and occupation based social classes. Unconditional logistic regression techniques were used to estimate relative risk and 95% confidence intervals (95% CIs) of ADL disability.

RESULTS

Compared with people who were former legislators, government administrators, or business executives and managers, workers in agriculture, animal husbandry, forestry, or fishing (odds ratio (OR) 1.9, 95% CI 1.1 to 3.5) and workers in craft and related trades (OR 1.9, 95% CI 1.1 to 3.4) had significantly increased risks of subsequent ADL disability. Differential risks of ADL disability were found across social classes, with a significant dose-response trend in which unskilled blue collar workers had an 1.8 times higher risk of ADL disability than higher social classes of white collar workers.

CONCLUSIONS

After adjustment for education, there was still an inverse relation between risk of ADL disability and social class. Although total control for all the known risk factors for ADL disability among elderly people was impossible, the results tend to suggest a potential for an effect of longest held occupation in a lifetime on risk of ADL disability.