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Biomedical subjects

Lewis A Lipsitz

Publications and source records attributed to Lewis A Lipsitz.

44 records · Page 3Linked to original sources
PubMed2002

Does aspirin attenuate the effect of angiotensin-converting enzyme inhibitors on health outcomes of very old patients with heart failure?

OBJECTIVES: Concomitant ischemic heart disease (IHD) is common in older individuals with heart failure (HF). We estimated the effect of aspirin use on the rate of mortality, morbidity, and decline in physical functioning in nursing home residents with HF taking angiotensin-converting enzyme (ACE) inhibitors. DESIGN: We conducted a retrospective cohort study using a nursing home database linking resident information collected via the Minimum Data Set (MDS) with drug utilization data. SETTING: Nursing homes in four states (1992-1995). PARTICIPANTS: Of 49,779 residents with HF admitted to these homes, 12,703 residents were taking an ACE inhibitor; 2,046 of these took aspirin. MEASUREMENTS: Medicare enrollment files provided the date of death, and we used the Part A Medicare files to identify hospital admissions. The activity of daily living scale from repeat MDS assessments allowed us to evaluate decline in physical function. Cox proportional hazards models provided adjusted estimates of the aspirin effect, with nonusers as the reference group. RESULTS: The overall mortality rate, hospitalization rate,and rate of decline in physical function of aspirin users were not different from those of nonusers (e.g., hospitalization rate ratio = 0.99, 95% confidence interval = 0.92-1.07). This effect did not vary by presence of concomitant IHD or by dose or type of ACE inhibitor. CONCLUSION: In a cohort of older HF residents receiving ACE inhibitors in nursing homes, we found that treatment with aspirin did not appear to affect outcomes negatively.

Activities of Daily Living↗
PubMed2002

Noise-enhanced vibrotactile sensitivity in older adults, patients with stroke, and patients with diabetic neuropathy.

OBJECTIVE: To test the hypothesis that vibrotactile detection thresholds in older adults, patients with stroke, and patients with diabetic neuropathy can be significantly reduced with the introduction of mechanical noise. DESIGN: A randomized controlled study. SETTING: A university research laboratory. PARTICIPANTS: Twelve healthy elderly subjects (age range, 67-85y), 5 patients with stroke (age range, 24-64y), and 8 patients with diabetic neuropathy (age range, 53-77y). INTERVENTIONS: Each subject's detection thresholds (ie, minimum level of stimulus to be detected) for a vibrotactile stimulus without and with mechanical noise (ie, random vibration with a small intensity) were determined by using a 4-, 2-, and 1-stepping algorithm. The stimuli were applied to the fingertip and/or to the first metatarsal of the foot. MAIN OUTCOME MEASURE: Detection threshold for a vibrotactile stimulus. RESULTS: The detection threshold at the fingertip for the vibration stimulus with mechanical noise was significantly lower than that without mechanical noise for all 12 elderly subjects, for 4 of the 5 patients with stroke, and all 8 patients with diabetic neuropathy. For the 8 patients with diabetes, mechanical noise also significantly reduced the vibrotactile detection threshold at the foot. CONCLUSIONS: Reduced vibrotactile sensitivity in older adults, patients with stroke, and patients with diabetic neuropathy can be significantly improved with input mechanical noise. Noise-based techniques and devices may prove useful in overcoming age- and disease-related losses in sensorimotor function.

Adult↗
PubMed2002

Dynamics of stability: the physiologic basis of functional health and frailty.

Under basal resting conditions most healthy physiologic systems demonstrate highly irregular, complex dynamics that represent interacting regulatory processes operating over multiple time scales. These processes prime the organism for an adaptive response, making it ready and able to react to sudden physiologic stresses. When the organism is perturbed or deviates from a given set of boundary conditions, most physiologic systems evoke closed-loop responses that operate over relatively short periods of time to restore the organism to equilibrium. This transiently alters the dynamics to a less complex, dominant response mode, which is denoted "reactive tuning." Aging and disease are associated with a loss of complexity in resting dynamics and maladaptive responses to perturbations. These alterations in the dynamics of physiologic systems lead to functional decline and frailty. Nonlinear mathematical techniques that quantify physiologic dynamics may predict the onset of frailty, and interventions aimed toward restoring healthy dynamics may prevent functional decline.

Aged↗
PubMed2002

Quantifying fractal dynamics of human respiration: age and gender effects.

We sought to quantify the fractal scaling properties of human respiratory dynamics and determine whether they are altered with healthy aging and gender. Continuous respiratory datasets (obtained by inductive plethysmography) were collected from 40 healthy adults (10 young men, 10 young women, 10 elderly men, and 10 elderly women) during 120 min of spontaneous breathing. The interbreath interval (IBI) time series were extracted by a new algorithm and fractal scaling exponents that quantify power-law correlations were computed using detrended fluctuation analysis. Under supine, resting, and spontaneous breathing conditions, both healthy young and elderly subjects had scaling exponents for the IBI time series that indicate long-range (fractal) correlations across multiple time scales. Furthermore, the scaling exponents (mean +/- SD) for the IBI time series were significantly (p < 0.03) lower (indicating decreased correlations) in the healthy elderly male (0.60 +/- 0.08) compared to the young male (0.68 +/- 0.07), young female (0.70 +/- 0.07), and elderly female (0.67 +/- 0.06) subjects. These results provide evidence for fractal organization in physiologic human breathing cycle dynamics, and for their degradation in elderly men. These findings may have implications for modeling integrated respiratory control mechanisms, quantifying their changes in aging or disease, and assessing the outcome of interventions aimed toward restoring normal physiologic respiratory dynamics.

Adult↗
PubMed2002

Dynamics of cerebral blood flow regulation explained using a lumped parameter model.

The dynamic cerebral blood flow response to sudden hypotension during posture change is poorly understood. To better understand the cardiovascular response to hypotension, we used a windkessel model with two resistors and a capacitor to reproduce beat-to-beat changes in middle cerebral artery blood flow velocity (transcranial Doppler measurements) in response to arterial pressure changes measured in the finger (Finapres). The resistors represent lumped systemic and peripheral resistances in the cerebral vasculature, whereas the capacitor represents a lumped systemic compliance. Ten healthy young subjects were studied during posture change from sitting to standing. Dynamic variations of the peripheral and systemic resistances were extracted from the data on a beat-to-beat basis. The model shows an initial increase, followed approximately 10 s later by a decline in cerebrovascular resistance. The model also suggests that the initial increase in cerebrovascular resistance can explain the widening of the cerebral blood flow pulse observed in young subjects. This biphasic change in cerebrovascular resistance is consistent with an initial vasoconstriction, followed by cerebral autoregulatory vasodilation.

Blood Pressure↗
PubMedDate not supplied

The microvascular frontal-subcortical syndrome of aging.

Many features of aging suggest dysfunction in both frontal and subcortical regions. Connections between the two areas form a series of pathways that critically influence various aspects of cognition, motor control, affect, and as recently discovered, normal urinary function. Age-related changes in the structure and integrity of these circuits may be associated with cognitive impairment, mood disorders, loss of balance, falls, and urinary dysfunction. In addition, cardiovascular risk factors in elderly people are associated with the development of cerebral microangiopathic changes in both the periventricular white matter and basal ganglia. These lesions are common, usually unsuspected, and were previously believed to be clinically innocuous. However, increasing evidence supports a role for these lesions as a cause for both dysfunction in frontal-subcortical systems, and many clinical features of aging that account for substantial disability. Because this form of cerebrovascular disease is potentially preventable, interventions that address risk factors for the development of cerebral microangiopathy may go a long way in preventing disability for the next generation of elderly persons.

Aging↗