Findings from three methods to identify falls in hospitals: Results from the Ambient Intelligent Geriatric Management system fall prevention trial.

OBJECTIVE: To (a) compare characteristics of patients who fall with those of patients who did not fall; and (b) characterise falls (time, injury severity and location) through three fall reporting methods (incident system reports, medical notes and clinician reports). METHODS: A substudy design within a stepped-wedge clinical trial was used: 3239 trial participants were recruited from two inpatient Geriatric Evaluation and Management Units and one general medicine ward in two Australian states. To compare the characteristics of patients who had fallen with those who had not, descriptive tests were used. To characterise falls through three reporting methods, bivariate logistic regressions were used. RESULTS: Patients who had fallen were more likely than patients who had not fallen to be cognitively impaired (51% vs. 29%, p < 0.01), admitted with falls (38% vs. 28%, p = 0.01) and have poor health outcomes such as prolonged length of stay (24 [16-34] vs. 12 [8-19] days [IQR], p < 0.01) and less likely to be discharged directly to the community (62% vs. 47%, p < 0.01). Most falls were captured from medical notes (93%), with clinician (71%) and incident reports (68%) missing 21%-25% of falls. The proportion of injurious falls identified through incident reports was higher than medical records or clinician reports (40% vs. 34% vs. 37%). CONCLUSIONS: This study reaffirms the need to improve reporting falls in incident systems and at clinical handover to the team leader. Research should continue to use more than one method of identifying falls, but include data from medical records. Many falls cause injury, resulting in poor health outcomes.

The Effect of the ENJOY Seniors Exercise Park Physical Activity Program on Falls in Older People in the Community: A Prospective Pre-Post Study Design.

BACKGROUND: The ENJOY project (Exercise interveNtion outdoor proJect in the cOmmunitY for older people) is a community-based research project actively promoting physical activity engagement through the delivery of an exercise program using outdoor multimodal exercise equipment. This study investigated the impact of the physical activity program on falls in older people. METHOD: This study was a multi-site prospective study with a pre-post intervention design and 12-month follow up. Eighty older people with increased falls risk underwent a 12-week supervised outdoors exercise program followed by a 6-month maintenance phase. The proportion of fallers and falls incidence were compared between the preceding and the prospective years. RESULTS: A sample of 54 (age 72.4±7.3, 79.6% women) was available for the 12 months analysis (due to COVID19 lockdowns, data of 19 participants were excluded and 4 dropped out). Number of fallers (from 51.8% to 31.4%, p=0.03) and falls incidence (from 42 to 29 falls, p<0.01) were significantly reduced at the 12-months follow up. CONCLUSION: The ENJOY Seniors Exercise Park program integrates outdoor multimodal exercise stations including specific exercises designed to challenge dynamic balance during functional daily movements. The outcomes provide preliminary evidence for the potential positive impact of the ENJOY Seniors Exercise Park in reducing falls for older people.

Risk factors for falls in patients with total hip arthroplasty and total knee arthroplasty: a systematic review and meta-analysis.

OBJECTIVE: Falls are common after total hip arthroplasty (THA) and total knee arthroplasty (TKA). While previous studies have investigated various risk factors for falls in patients following THA and TKA, no systematic reviews have summarized these risk factors. Therefore, the current systematic review aimed to summarize evidence regarding risk factors for falls in patients after THA and/or TKA. METHODS: MEDLINE, EMBASE, CINAHL, SPORTDiscus, and Physiotherapy Evidence Database (from inception to June 30, 2018) were searched. The methodological quality and quality of evidence of the included studies were assessed by two independent reviewers. Relevant data regarding participants' characteristics, study design, follow-up time points, and identified risk factors were extracted. Meta-analyses and narrative syntheses were performed. RESULTS: Twelve studies with a total of 1,292,689 participants were included. Twenty-nine identified risk factors for post-THA/TKA falls were classified into either inpatient or post-discharge risk factors. Key risk factors for both post-THA and/or post-TKA inpatient falls that showed moderate level of evidence included: postoperative complications or comorbidities and revision THA/TKA. Likewise, risk factors for post-discharge falls after THA and/or TKA that demonstrated moderate level of evidence included: medications, psychiatric diseases, living alone, prior history of TKA, falls history and female gender. The quality of the included studies varied and sample sizes were not justified. CONCLUSIONS: This review summarized both non-modifiable and modifiable risk factors for post-THA/TKA falls. Our findings highlight the importance of developing strategies to lower the falls risk among patients following THA/TKA.

Build better bones with exercise (B3E pilot trial): results of a feasibility study of a multicenter randomized controlled trial of 12 months of home exercise in older women with vertebral fracture.

We pilot-tested a trial of home exercise on individuals with osteoporosis and spine fracture. Our target enrollment was met, though it took longer than expected. Participants stayed in the study and completed the exercise program with no safety concerns. Future trials should expand the inclusion criteria and consider other changes. PURPOSE: Osteoporotic fragility fractures create a substantial human and economic burden. There have been calls for a large randomized controlled trial examining the effect of exercise on fracture incidence. The B3E pilot trial was designed to evaluate the feasibility of a large trial examining the effects of home exercise on individuals at high risk of fracture. METHODS: Community-dwelling women ≥ 65 years with radiographically confirmed vertebral compression fractures were recruited at seven sites in Canada and Australia. We randomized participants in a 1:1 ratio to a 12-month home exercise program or equal attention control group, both delivered by a physiotherapist (PT). Participants received six PT home visits in addition to monthly phone calls from the PT and a blinded research assistant. The primary feasibility outcomes of the study were recruitment rate (20 per site in 1 year), retention rate (75% completion), and intervention adherence rate (60% of weeks meeting exercise goals). Secondary outcomes included falls, fractures and adverse events. RESULTS: One hundred forty-one participants were recruited; an average of 20 per site, though most sites took longer than anticipated. Retention and adherence met the criteria for success: 92% of participants completed the study; average adherence was 66%. The intervention group did not differ significantly in the number of falls (IRR 0.97, 95% CI 0.58 to 1.63) or fragility fractures (OR 1.11, 95% CI 0.60 to 2.05) compared to the control group. There were 18 serious adverse events in the intervention group and 12 in the control group. CONCLUSION: An RCT of home exercise in women with vertebral fractures is feasible but recruitment was a challenge. Suggestions are made for the conduct of future trials.

Bone loss with antiepileptic drug therapy: a twin and sibling study.

Changes in areal bone mineral density (aBMD) and other predictors of bone loss were evaluated in 48 same-sex twin/age-matched sibling pairs discordant for antiepileptic drug (AED) use. AED users had reduced BMD at the hip regions. Prolonged AED users had greater aBMD loss, predicting a higher risk of bone fragility. INTRODUCTION: To investigate the longitudinal associations of bone mineral measures with antiepileptic drug (AED) use, including enzyme-inducing (EIAED) and non-enzyme-inducing (NEIAED) types, and other predictors of bone loss in a study of 48 same-sex twin/age-matched sibling pairs (40 female, 8 male) discordant for AED use. METHODS: Using dual-energy X-ray absorptiometry (DXA), areal bone mineral density (aBMD) and content (BMC) at the hip regions, forearm, lumbar spine, and whole body were measured twice, at least 2 years apart. The mean within-pair difference (MWPD), MWPD%, and mean annual rate of aBMD change were adjusted for age, weight, and height. Predictors of bone loss were evaluated. RESULTS: AED users, compared to non-users, at baseline and follow-up, respectively, had reduced aBMD at the total hip (MWPD% 3.8, 4.4%), femoral neck (4.7, 4.5%), and trochanter regions (4.1, 4.6%) (p < 0.05). For the whole cohort, the annual rate of change in all aBMD/BMC (p > 0.05) regions did not differ within pairs. Nevertheless, EIAED users had greater aBMD loss than non-users (n = 20 pairs) at the total hip (1.7 vs. 0.3%, p = 0.013) and whole body regions (0.7% loss vs. 0.1% BMD gain, p = 0.019), which was not found in NEIAED-discordant pairs (n = 16). AED use >20 years predicted higher aBMD loss at the forearm (p = 0.028), whole body (p = 0.010), and whole body BMC (p = 0.031). CONCLUSIONS: AED users had reduced aBMD at the hip regions. Prolonged users and EIAED users had greater aBMD loss, predicting a higher risk of bone fragility. Further prospective studies of AED effects on bone microarchitecture are needed.

RESPOND: a programme to prevent secondary falls in older people presenting to the emergency department with a fall: protocol for an economic evaluation.

BACKGROUND: Falls remain common for community-dwelling older people and impose a substantial economic burden to the healthcare system. RESPOND is a novel falls prevention programme that aims to reduce secondary falls and fall injuries among older people who present to a hospital emergency department (ED) with a fall. The present protocol describes a prospective economic evaluation examining the incremental cost-effectiveness of the RESPOND programme, compared with usual care practice, from the Australian health system perspective. METHODS AND DESIGN: This economic evaluation will recruit 528 participants from two major tertiary hospital EDs in Australia and will be undertaken alongside a multisite randomised controlled trial. Outcome and costing data will be collected for all participants over the 12-month trial. It will compare the RESPOND falls prevention programme with usual care practice (current community-based falls prevention practices) to determine its incremental cost-effectiveness according to three intermediate clinical outcomes: (1) falls prevented, (2) fall injuries prevented and (3) injurious falls prevented. In addition, utilities will be derived from a generic quality-of-life measure (EQ-5D-5L) and used to calculate the 'incremental cost per quality-adjusted life years gained'. DISCUSSION: The results of this study will provide healthcare decision makers with evidence to assist with setting spending thresholds for preventive health programmes and inform selection of emergency and community service models of care. TRIAL REGISTRATION NUMBER: The protocol for this study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12614000336684); Pre-results.

Older Adult Perceptions of Participation in Group- and Home-Based Falls Prevention Exercise.

This paper describes why older adults begin, continue, and discontinue group- and home-based falls prevention exercise and benefits and barriers to participation. Telephone surveys were used to collect data for 394 respondents. Most respondents reported not participating in group- (66%) or home-based (78%) falls prevention exercise recently. Reasons for starting group-based falls prevention exercise include health benefits (23-39%), health professional recommendation (13-19%), and social interaction (4-16%). They discontinued because the program finished (44%) or due to poor health (20%). Commonly reported benefits were social interaction (41-67%) and health (15-31%). Disliking groups was the main barrier (2-14%). Home-based falls prevention exercise was started for rehabilitation (46-63%) or upon health professional recommendation (22-48%) and stopped due to recovery (30%). Improvement in health (18-46%) was the main benefit. These findings could assist health professionals in prescribing group-based falls prevention exercise by considering characteristics of older adults who perceive social interaction to be beneficial.

RESPOND: a patient-centred programme to prevent secondary falls in older people presenting to the emergency department with a fall-protocol for a mixed methods programme evaluation.

BACKGROUND: Programme evaluations conducted alongside randomised controlled trials (RCTs) have potential to enhance understanding of trial outcomes. This paper describes a multi-level programme evaluation to be conducted alongside an RCT of a falls prevention programme (RESPOND). OBJECTIVES: (1) To conduct a process evaluation in order to identify the degree of implementation fidelity and associated barriers and facilitators. (2) To evaluate the primary intended impact of the programme: participation in fall prevention strategies and the factors influencing participation. (3) To identify the factors influencing RESPOND RCT outcomes: falls, fall injuries and emergency department (ED) re-presentations. METHODS/DESIGN: 528 community-dwelling adults aged 60-90 years presenting to two EDs with a fall will be recruited and randomly assigned to the intervention or standard care group. All RESPOND participants and RESPOND clinicians will be included in the evaluation. A mixed methods design will be used and a programme logic model will frame the evaluation. Data will be sourced from interviews, focus groups, questionnaires, clinician case notes, recruitment records, participant-completed calendars, hospital administrative datasets and audio-recordings of intervention contacts. Quantitative data will be analysed via descriptive and inferential statistics and qualitative data will be interpreted using thematic analysis. DISCUSSION: The RESPOND programme evaluation will provide information about contextual and influencing factors related to the RESPOND RCT outcomes. The results will assist researchers, clinicians and policy makers regarding decisions about future falls prevention interventions. Insights gained may be applicable to a range of chronic conditions where similar preventive intervention approaches are indicated. TRIAL REGISTRATION NUMBER: This programme evaluation is linked to the RESPOND RCT which is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12614000336684).

Differences in Eccentricity Index and Systolic-Diastolic Ratio in Extremely Low-Birth-Weight Infants with Bronchopulmonary Dysplasia at Risk of Pulmonary Hypertension.

OBJECTIVE: To compare the left ventricular eccentricity index (EI) and tricuspid valve systolic-diastolic (SD) ratio in infants at risk of bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH). STUDY DESIGN: Review of echocardiograms performed on infants born at ≤ 28 weeks' postmenstrual age, categorized into the following three cohorts: BPD and PH (n = 13); BPD only (n = 16); and controls (n = 59). EI was measured from a parasternal short axis 2D image. The SD ratio was measured from the continuous wave Doppler tracing. Groups were compared using Kruskal-Wallis and Wilcoxon rank sum tests. RESULT: EI and SD ratios were successfully measured in all infants. There were no differences between controls and BPD cohort. In contrast, the BPD and PH cohort had increased systolic EI (1.46 vs. 1.00-1.01), diastolic EI (1.47 vs. 1.00), and SD ratio (1.12 vs. 0.97-1.00) compared with controls and BPD only cohort (p ≤ 0.01 for all). CONCLUSION: The EI and SD ratio may be useful as a screening tool for PH in this population.

RESPOND--A patient-centred programme to prevent secondary falls in older people presenting to the emergency department with a fall: protocol for a multicentre randomised controlled trial.

INTRODUCTION: Participation in falls prevention activities by older people following presentation to the emergency department (ED) with a fall is suboptimal. This randomised controlled trial (RCT) will test the RESPOND programme, an intervention designed to improve older persons' participation in falls prevention activities through delivery of patient-centred education and behaviour change strategies. DESIGN AND SETTING: A RCT at two tertiary referral EDs in Melbourne and Perth, Australia. PARTICIPANTS: 528 community-dwelling people aged 60-90 years presenting to the ED with a fall and discharged home will be recruited. People who require an interpreter or hands-on assistance to walk; live in residential aged care or >50 km from the trial hospital; have terminal illness, cognitive impairment, documented aggressive behaviour or a history of psychosis; are receiving palliative care or are unable to use a telephone will be excluded. METHODS: Participants will be randomly allocated to the RESPOND intervention or standard care control group. RESPOND incorporates (1) a home-based risk factor assessment; (2) education, coaching, goal setting and follow-up telephone support for management of one or more of four risk factors with evidence of effective interventions and (3) healthcare provider communication and community linkage delivered over 6 months. Primary outcomes are falls and fall injuries per person-year. DISCUSSION: RESPOND builds on prior falls prevention learnings and aims to help individuals make guided decisions about how they will manage their falls risk. Patient-centred models have been successfully trialled in chronic and cardiovascular disease; however, evidence to support this approach in falls prevention is limited. TRIAL REGISTRATION NUMBER: The protocol for this study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12614000336684).

BILATERAL KEY COMPARISON SIM.T-K6.1 ON HUMIDITY STANDARDS IN THE DEW/FROST-POINT TEMPERATURE RANGE FROM -25 °C TO +20 °C.

A Regional Metrology Organization (RMO) Key Comparison of dew/frost point temperatures was carried out by the National Institute of Standards and Technology (NIST, USA) and the National Research Council (NRC, Canada) between December 2014 and April, 2015. The results of this comparison are reported here, along with descriptions of the humidity laboratory standards for NIST and NRC and the uncertainty budget for these standards. This report also describes the protocol for the comparison and presents the data acquired. The results are analyzed, determining degree of equivalence between the dew/frost-point standards of NIST and NRC.

The long-term benefits of a multi-component exercise intervention to balance and mobility in healthy older adults.

We examined the long-term effects of a multi-component exercise program on balance, mobility and exercise behavior. The benefits of a community-based resistance and flexibility exercise intervention in a group of healthy older (60-75 years) individuals were recorded 12 months after completion of the randomized control intervention. Differences between those participants who continued to exercise and those who discontinued were investigated. Significant improvements from baseline in sit to stand (p<0.001), timed up and go (p=0.001), and sway (p<0.001) remained at follow up in the exercise intervention group, with a control group unchanged. Participants who continued exercising had significantly greater improvements in strength immediately after the intervention, compared to those who discontinued (p=0.004). Those who continued regular resistance training performed better in the step test at 12-month follow up (p=0.009) and believed that the program was of more benefit to their physical activity (p<0.001) than those who discontinued exercising. Benefits to balance and mobility persist 1 year after participation in a multi-component exercise program, due in part to some continuing participation in resistance training. Motivation to continue resistance training may be related real and perceived benefits attained from the intervention as well as the environmental context of the intervention.

Systematic and random error in repeated measurements of temporal and distance parameters of gait after stroke.

OBJECTIVE: To obtain intersession estimates of error for temporal and distance (TD) parameters of gait in a sample of stroke patients undertaking inpatient rehabilitation. DESIGN: Thirty-one stroke patients were measured with an instrumented footswitch system (after a median of 46 days poststroke; interquartile range = 26 to 63) walking over a 10-meter distance a total of four times on 3 consecutive days. Two familiarization walks provided intrasession retest data. RESULTS: Metric estimates of systematic and random error have been provided for obtained TD parameters. Proportional indices of reliability (ICC [2,1] and Pearson's r) were generally high, ranging from .72 to .94. CONCLUSION: By quantifying systematic and random error associated with the process of repeated measurements, criteria have been provided for evaluating change in TD variables during rehabilitation. Although error for gait velocity was small relative to individual differences in the stroke group, it was large relative to levels of change derived from measurements reported during typical periods of rehabilitation. Serial measurements of gait during rehabilitation may be better than two consecutive measurements. This study highlights the need to interpret estimates of error according to the purpose of measurement.

Fear of falling revisited.

OBJECTIVE: To evaluate the measurement properties of an expanded version of the Falls Efficacy Scale (FES)-a measure of fear of falling. The original FES measures fear on almost exclusively indoor activities, which may limit the usefulness of the scale in identifying early stages of fear of falling in active community-dwelling older people. DESIGN: Two-group convenience sample. SETTING: An outpatient referral clinic, and community-dwelling older people recruited from various sources. SUBJECTS: A volunteer sample of 111 healthy community-dwelling elderly (mean age 74.0 years) and a sample of 68 older people referred to a Falls and Balance Clinic (FBC) (mean age 79.2). Twenty-one subjects (9 healthy elderly and 12 FBC patients) were tested twice 1 week apart to investigate retest reliability. MAIN OUTCOME MEASURES: A 14-activity questionnaire (the Modified Falls Efficacy Scale [MFES]) was used that incorporated the original 10-activity FES and four additional activities. Falls efficacy was rated on a 10-point visual analogue scale for each activity. RESULTS AND CONCLUSIONS: The MFES demonstrated high internal consistency (Cronbach's alpha.95) and less skew than the original FES (-2.4 and -3.3, respectively). Factor analysis of the MFES revealed two factors accounting for 75% of the sample variance, grouping into an "indoor type activity" factor and an "outdoor type activity" factor. Retest reliability for the MFES was high (intraclass correlation coefficients = .93). Significant differences were evident between the FBC group and the healthy older group on all items of the MFES and on the total MFES score (p < .05). On the basis of these preliminary findings, the MFES appears to be a reliable and valid measure of falls self-efficacy, and could be a useful addition in the comprehensive assessment of older people with balance disturbance or falls.

A falls and balance clinic for the elderly.

A Falls and Balance Clinic for the elderly has been developed with the aim of identifying those at risk of subsequent falls, and recommending intervention strategies to reduce this risk. The physical and functional status of 149 clients referred to the Clinic are reported. Neurological and musculoskeletal pathologies were identified as the cause of falls in the majority of clients. Measures of gait velocity and stride length, and ability to stand on one leg were markedly reduced compared with normative data for healthy elderly. A number of other measures of balance, strength, and function are also reported. The results of a questionnaire about home environment indicated that only 28% of those referred had been assessed in their own home in the previous year. Home environment was considered a potential risk in a further 28% of clients and a home visit was instituted in these cases. Other intervention strategies included referral for further investigations (36%), Day Hospital (33%), provision of a home program of balance or strengthening exercises (27%), and medication change (15%). Issues related to the establishment, operation and long term evaluation of the effectiveness of a specialist Falls and Balance Clinic for the elderly are discussed.

Retest reliability of the temporal and distance characteristics of hemiplegic gait using a footswitch system.

Using a footswitch system, the retest reliability of the temporal and distance parameters of gait was investigated within a session for 22 stroke patients in the early phase of rehabilitation. High to very high reliability was found for the temporal and distance parameters of gait, and the temporal symmetry index based on the difference in single-limb support duration between each leg (r = 0.85 to 0.98; intraclass correlation coefficients (ICC)(2,1) = 0.82 to 0.98). Significant differences were found between the two trials for velocity, stride length, and total double support (p < .05). Despite the high reliability coefficients, 95% confidence intervals, which take into account the random and systematic error, were wide for all parameters. These wide confidence intervals indicate that the use of two consecutive measurements for interpreting an individual patient's change would not be a sensitive method for monitoring progress or deterioration during rehabilitation. Strategies that may improve the clinical usefulness of temporal and distance gait measures in stroke rehabilitation are discussed. These include further reducing error sources, increasing data collection per measurement, using serial measurements on each patient, or using less rigorous confidence intervals.

High-performance liquid chromatographic column-switching technique for the determination of intermediates of anaerobic degradation of toluene in ground water microcosm.

A reversed-phase liquid chromatographic column-switching system was used for the determination of phenol, benzoic acid and cresol (PBC) in the presence of toluene in ground water microcosm. A precolumn was connected in series with an analytical column via a column-switching valve. After the injection, as soon as PBC were eluted from the precolumn to the analytical column, the valve was switched so that the precolumn was between the analytical column and the UV detector. Toluene and other non-polar compounds were eluted from the precolumn in a very short time and detected along with the solvent front. Subsequently, PBC were separated on the analytical column and passed through the precolumn one more time before being detected by the UV detector. The total analysis time was 15 min. This technique facilitated the study of the basic mechanism and path way of anaerobic degradation of toluene in ground water aquifer.

Use of ion-exclusion chromatography for monitoring fatty acids produced by bacterial anaerobic degradation of tetrachloroethene in ground water.

A rapid method for the simultaneous quantification of non-volatile and volatile fatty acids in aqueous sample by ion-exclusion chromatography is described. The sample is directly injected into the column and detected by a chemically suppressed conductivity detector, connected in tandem with an UV detector at 210 nm. The method allows detection of fatty acid as low as 1 ppm with a linear dynamic range up to 1000 ppm. At least 13 fatty acids can be determined within 50 min. This technique has been used to monitor the common fermentation products (lactate, acetate, propionate and butyrate) of the reductive dehalogenation of tetrachloroethene by anaerobic bacteria.

Similarity of urinary risk factors among stone-forming patients in five regions of the United States.

STUDY OBJECTIVE: To compare urinary biochemical risk factors among stone-forming patients in the Southeast (SE) or "stone belt" versus four other regions of the United States. DESIGN: Prospective biochemical survey for regional comparisons. SETTING: Referral-based nephrolithiasis clinics, urologists, nephrologists, and family practitioners. PATIENTS: Consecutive sample of 3473 stone-forming patients who submitted 24-hour urine collections for biochemical analyses of stone-forming risk factors. INTERVENTIONS: None. Subjects taking medication known to interfere with stone-forming risk factors were deleted from the final data compilation. MEASUREMENTS AND MAIN RESULTS: Overall, the mean values for each urinary parameter spanned a narrow range without significant difference between the five regions. Among "metabolic" factors, 40% in the SE had hypercalciuria (> 6.25 mmol/d), compared to 35%-43% in other regions, and hyperuricosuria (> 4.2 mmol/d) was found in 16% in the SE versus 17%-19% elsewhere. Among "environmental" factors, low urine volume ( < 2 L/d) was found in 77% patients in the SE compared to 69%-78% elsewhere, and high sodium was encountered in 27% in the SE versus 24%-29% elsewhere. No differences were noted in occurrence of other abnormal risk factors: hyperoxaluria, hypocitraturia, low pH, high sulfate, high phosphorus, or low magnesium. CONCLUSIONS: Despite expected regional differences in nutritional and environmental influences, the results of this study showed a striking similarity in urinary biochemical risk factor profiles of stone-formers in all five regions of the United States.

Relationship of animal protein-rich diet to kidney stone formation and calcium metabolism.

We wished to determine whether different types of dietary protein might have different effects on calcium metabolism and on the propensity for renal stone formation. Fifteen young normal subjects were studied during three 12-day dietary periods during which their diet contained vegetable protein, vegetable and egg protein, or animal protein. While these three diets were constant with respect to Na, K, Ca, P, Mg, and quantity of protein, they had progressively higher sulfur contents. As the fixed acid content of the diets increased, urinary calcium excretion increased from 103 +/- 15 ( +/- SEM) mg/day (2.6 +/- 0.4 mmol/day) on the vegetarian diet to 150 +/- 13 mg/day (3.7 +/- 0.3 mmol/day) on the animal protein diet (P less than 0.02). Despite the increased urinary calcium excretion, there was a modest reduction of urinary cAMP excretion and serum PTH and 1,25-dihydroxyvitamin D levels consistent with acid-induced bone dissolution. There was no change in fractional intestinal 47Ca absorption. The inability to compensate for the animal protein-induced calciuric response may be a risk factor for the development of osteoporosis. The animal protein-rich diet was associated with the highest excretion of undissociated uric acid due to the reduction in urinary pH. Moreover, citrate excretion was reduced because of the acid load. However, oxalate excretion was lower than during the vegetarian diet [26 +/- 1 mg/day (290 +/- 10 mumol/day) vs. 39 +/- 2 mg/day (430 +/- 20 mumol/day); P less than 0.02]. Urinary crystallization studies revealed that the animal protein diet, when its electrolyte composition and quantity of protein were kept the same as for the vegetarian diet, conferred an increased risk for uric acid stones, but, because of opposing factors, not for calcium oxalate or calcium phosphate stones.