Association between walking 5000 step/day and fall incidence over six months in urban community-dwelling older people.

BACKGROUND: Walking is the most common population-wide campaign for health promotion in older people. However, the cutoff threshold for walking steps/day to identify the older people who are at risk of falling is not recommended. Therefore, the objectives were to investigate the association between all possible risk factors including physical performance, physical activity and fall incidence over the six-month in community-dwelling older people who had low-risk of falling and to identify walking threshold (steps/day) for reducing risk of fall. METHODS: The older people who aged ≥60 years and had free of falling for 1 year were invited to participate in this study. They lived in five communities in Bangkok Thailand. Demographics and physical performances were collected at baseline. Walking (step/day) and 24-h physical activity (PA) were monitored for 5 consecutive days by the Actical® accelerometer wrapped on non-dominant wrists. The Physical Activity Scale for the Elderly (PASE) questionnaire was used to record activities in the past 7 days by interview. A monthly calendar was used to record fall incidence over the 6 months. Unadjusted and adjusted hazard ratio (HR) with 95% confidence interval (CI) were analyzed using the Cox's proportional hazard regression. The Kaplan Meier curve illustrated the probability to survive from fall over the 6 months. RESULTS: Of 255, 33 older people (12.94%) reported first-fall incidence over the 6 months. Fall incidence density rate was 0.79 per 1000 person-day. Our findings showed that significant association between fall incidence and behavioral risk factors including PASE scores < 100 (HR = 3.53; 95% CI: 1.24-10.04), walking < 5000 steps/day (HR = 3.6; 95% CI: 1.76-7.31) and moderate to vigorous intensity of PA at < 60 min/week (HR = 3.66; 95% CI: 1.12-12.01). Fall incidence were related to the following risk factors: age (HR = 3.54; 95% CI: 1.37-9.11), took polypharmacy/antipsychotics (HR = 4.32; 95% CI: 2.12-8.79), presence of urinary incontinence (HR = 2.87; 95% CI: 1.45-5.68), low functional mobility by Timed Up and Go ≥13.5 s (HR = 6.43; 95% CI: 2.65-15.57). CONCLUSIONS: This study proposed walking ≥5000 steps/day as a cutoff threshold to recommend for reducing risk of falling in community-dwelling older people who had low-risk of falling.

Reduction-mediated 99mTc-labeling of antitumor monoclonal antibodies: effect of increasing specific activity on antibody binding kinetics.

Reduction-mediated 99mTc-labeling of antibodies has gained widespread acceptance in preparation of tumor imaging agents. Increased specific activity to enhance detection signals has raised the question of whether such an attempt would cause change in antibody binding kinetics. To answer this question, two antitumor monoclonal antibodies, i.e. IOR-CEA (IgG1) and EMD (IgG2a) were labeled with 99mTc to yield specific activities ranging from 549-4414 MBq/mg. Regression analysis of the binding data revealed that the binding kinetics of IOR-CEA were shifted from monovalent to bivalent binding upon increasing the specific activities. This phenomenon of affinity enhancement was confirmed by the dissociation study where we found soluble CEA had greater difficulty in extracting the cell-bound IOR-CEA labeled at higher specific activity. The bivalent bindings was further supported by the finding that IOR-CEA with higher specific activities delivered less than expected radioactivity to tumor targets despite their immunoreactivities being well preserved. For EMD, the kinetics seemed to be shifted from bivalent to monovalent interaction. At higher specific activities, adverse changes in immunoreactivity were recognized. Breakage of EMD into 99mTc-Fab fragments was likely to occur and was supported by the observation that EMD delivered more than expected radioactivities to target cells upon increasing specific activity. Precaution should be taken when one deals with high specific activity labeling since this might alter the antibody binding kinetics either favorably or unfavorably.