[The effect of specialised medical procedures on the hosptial standardised mortality ratio in cardiac centers]. / Hartcentra en het effect van bijzondere medische verrichtingen op het gestandaardiseerde ziekenhuissterftecijfer.

OBJECTIVE: To examine the impact of specialised medical procedures (SMPs) on the hospital standardized mortality ratio (HSMR) in Dutch cardiac centres. DESIGN: Retrospective, calculation of the HSMR. METHOD: Data from 2004 from the National Medical Registration (LMR) were used to calculate the HSMR in 12 cardiac centres and all other hospitals in the Netherlands. The HSMRwas then recalculated for the 12 cardiac centres excluding either percutaneous transluminal coronary angioplasty (PTCA) or open heart surgery or both to determine the impact of these SMPs on the HSMR. RESULTS: Exclusion of SMPs from the HSMR calculation changed the HSMR for individual cardiac centres, ranging from a 4.7% decrease to a 5.3% increase. Change in HSMR was related to the relative frequency of the two procedures at each cardiac centre. Mortality risk was lower than average for PTCA and higher than average for open heart surgery. PTCA accounted for 5.6%-20.2% of total admissions in the 12 cardiac centres. A relatively high proportion of PTCA procedures was associated with a lower HSMR, to a maximum decrease of nearly 7% in one cardiac centre. Open heart surgery accounted for 2.1%-12.6% of total admissions per cardiac centre. A relatively high proportion ofopen heart procedures was associated with an increased HSMR, to a maximum increase of nearly 8% in one cardiac centre. CONCLUSION: Specialised medical procedures for heart conditions influence the HSMR of cardiac centres. The increase or decrease in HSMR is related to the relative frequency of PTCA and open heart surgery. These results can be used to help interpret the differences in HSMR among cardiac centres and other hospitals.

[CBO guidelines to prevent accidental falls in the elderly: how can it be used in the institutionalized elderly?]. / CBO richtlijn preventie van valincidenten bij ouderen: wat kunnen verpleeghuizen hiermee?

Fall incidents occur frequently in the community dwelling elderly and even more in the institutionalised elderly. Fall-related research data indicate positive effects of a multifactorial intervention targeted on prevention of falls and fall-related injuries. In November 2004 the guideline "Prevention of fall incidents in the elderly" developed by The Dutch Institute for Healthcare Improvement (CBO) was published. This guideline pays attention to the risk factors for falling and the prevention of fall incidents in all settings. The highlights for nursing homes are: all nursing home patients are at risk; perform a fall risk assessment to direct fall preventive activities; together with specific fall prevention for the patient general fall prevention for the institute has to be undertaken; a multifactorial approach is indicated. In nursing homes it is possible to perform such approach multidisciplinary.

CBO Richtlijn Preventie van valincidenten bij ouderen: wat kunnen verpleeghuizen hiermee?

Fall incidents occur frequently in the community dwelling elderly and even more in the institutionalised elderly. Fall-related research data indicate positive effects of a multifactorial intervention targeted on prevention of falls and fall-related injuries.In November 2004 the guideline "Prevention of fall incidents in the elderly" developed by The Dutch Institute for Healthcare Improvement (CBO) was published. This guideline pays attention to the risk factors for falling and the prevention of fall incidents in all settings. The highlights for nursing homes are: 1.all nursing home patients are at risk;2.perform a fall risk assessment to direct fall preventive activities;3.together with specific fall prevention for the patient general fall prevention for the institute has to be undertaken;4.a multifactorial approach is indicated. In nursing homes it is possible to perform such approach multidisciplinary.

Daily physical activity and the use of a walking aid in relation to falls in elderly people in a residential care setting.

Physical activity is usually considered as an important component of a healthy lifestyle, including a preventive effect on the risk of falls in the elderly. The relationship between physical activity and falls is complex: physical activity is a prerequisite to maintain neuromuscular functioning, necessary to keep balance and to react to a fall, but a higher level of physical activity also implies a greater exposure to environmental threats, possibly leading to a fall. Related to this greater exposure to threats, the use of a walking aid may protect against falls in those who have impaired mobility. In this cross-sectional study we investigated the relationship between daily physical activity and falls and the use of a walking aid in elderly subjects. Participants were 131 men and 563 women, aged 70 years and over (mean age and standard deviation: 82+/-6 years), living in homes for the elderly (n=335) and apartment houses for elderly (n=359). Data on baseline characteristics and falls in the previous year were obtained using a questionnaire. The level of daily physical activity in the previous year was obtained by means of a questionnaire regarding household and leisure activities. Subjects with a lower extremity fracture in the previous year were excluded from the analyses. Data were analysed using multiple logistic regression, adjusted for age, gender, and residence. In the past year, 40% of the participants fell at least one time, and 19% of the participants fell two times or more. Since falls and recurrent falls were nonlinearly related to the level of daily physical activity, the physical activity score was grouped into quartiles: the highest quartile corresponding to the highest activity level. Odds ratios (and 95% confidence intervals) for falls and recurrent falls for subjects in the highest quartile contrasted with those in the lowest quartile were 0.5 (0.3-0.9) and 0.3 (0.2-0.6), respectively. The risk of falls and recurrent falls was not lower for those with intermediate levels of daily physical activity. The use of a walking aid protected against falls in those with intermediate high activity levels (third quartile). It was suggested that the exposure to environmental hazards, due to some degree of physical activity may have been responsible for the nonlinear relationship between daily physical activity and falling. We conclude that a high activity level and the use of a walking aid may protect against falls.

Suboptimal care and perinatal mortality in ten European regions: methodology and evaluation of an international audit.

BACKGROUND: A European concerted action (the EuroNatal study) investigated differences in perinatal mortality between countries of Europe. This report describes the methods used in the EuroNatal international audit and discusses the validity of the results. METHODS: Perinatal deaths between 1993 and 1998 in regions of ten European countries were identified. The categories of death chosen for the study were singleton fetal deaths at 28 or more weeks of gestational age, all intrapartum deaths at 28 or more weeks of gestational age and neonatal deaths at 34 or more weeks of gestational age. Deaths with major congenital anomalies were excluded. An international audit panel used explicit criteria to review all cases, which were blinded for region. Subjective interpretation was used in cases of events or interventions where explicit criteria did not exist. Suboptimal factors were identified in the antenatal, intrapartum and neonatal periods, and classified as 'maternal/social', due to 'infrastructure/service organization', or due to 'professional care delivery'. The contribution of each suboptimal factor to the fatal outcome was listed and consensus was reached on a final grade using a procedure that included correspondence and plenary meetings. RESULTS: In all regions combined, 90% of all known or estimated cases in the selected categories were included in the audit. In total, 1619 cases of perinatal death were audited. Consensus was reached in 1543 (95%) cases. In 75% of all cases, the grade was based on explicit criteria. In the remaining cases, consensus was reached within subpanels without reference to predefined criteria. There was reasonable to good agreement between and within subpanels, and within panel members. CONCLUSIONS: The international audit procedure proved feasible and led to consistent results. The results that relate to suboptimal care will need to be studied in depth in order to reach conclusions about their implications for assessing the quality of perinatal care in the individual regions.

The reliability of perinatal and neonatal mortality rates: differential under-reporting in linked professional registers vs. Dutch civil registers.

Official Dutch perinatal mortality rates are based on birth and death certificates. These civil registration data are not detailed enough for international comparisons or extensive epidemiological research. In this study, we linked and extrapolated three national, incomplete, professional registers from midwives, obstetricians and paediatricians, containing detailed perinatal information. This linkage and extrapolation resulted in one detailed professional database which is representative of all Dutch births and from which gestational age-specific perinatal mortality rates could be calculated. The reliability of these calculated mortality rates was established by comparing them with the rates derived from the national civil registers. The professional database reported more perinatal deaths and fewer late neonatal deaths than the civil registers. The under-reporting in the civil registers amounted to 1.2 fewer perinatal deaths per 1000 births and was most apparent in immature newborns. We concluded that under-reporting of perinatal and neonatal deaths depends on the data source used. Mortality rates for the purpose of national and international comparison should, therefore, be defined with caution. This study also demonstrated that combining different incomplete professional registers can result in a more reliable database containing detailed perinatal information. Such databases can be used as the basis for extensive perinatal epidemiological research.

Comparability of published perinatal mortality rates in Western Europe: the quantitative impact of differences in gestational age and birthweight criteria.

OBJECTIVE: To quantify the impact of publication criteria on differences in published national perinatal mortality rates among Western European countries. DESIGN: Descriptive study of perinatal mortality rates in Western European countries with adjustments for international differences in publication data. POPULATION: All live births and perinatal deaths in 1994 in Western European countries. METHODS: The 1994 perinatal mortality rates were obtained from national and Eurostat publications for Belgium, Denmark, Finland, France, Germany, Greece, The Netherlands. Norway, Portugal, Spain, Sweden, United Kingdom (England, Wales, Scotland, Northern Ireland). Two methods, one direct and one indirect, were used for adjusting these officially published rates for differences in registration laws or publication practices. For the indirect method adjustment factors were derived from an analysis of a large Finnish database using different cutoff points for gestational age and birthweight. For the direct method a common cutoff point was imposed for birthweight (1000g) and gestational age (28 completed weeks) on national perinatal mortality data, obtained from civil registration or hospital/obstetrics databases in each country. RESULTS: The published perinatal mortality rates ranged from 5.4 per 1000 total births in Sweden and Finland to 9.7 in Greece and Northern Ireland. The indirect adjustment method showed that some countries apply cutoff points for registration or publication of perinatal mortality which may raise the perinatal mortality rate by up to 17% above the most commonly used threshold for including live and stillbirths. The direct adjustment method showed that a common lower limit of 1000g for birthweight or 28 weeks for gestational age would reduce the perinatal mortality rate, but by a differing extent ranging from 14% to 40%. Both adjustment methods reduced the contrast between the countries' perinatal mortality rates, and changed their rank order. CONCLUSION: These quantitative results confirm that international differences in countries' published perinatal mortality rates partly reflect differences between countries' criteria for registration and publication of perinatal deaths.

Ultrasound measurements for the prediction of osteoporotic fractures in elderly people.

In this prospective study we investigated the predictive value of quantitative ultrasound (QUS) measurements and other potential predictors of osteoporotic fractures in the elderly. During a 1-year period, 710 participants (132 men and 578 women), aged 70 years and older (mean age +/- SD: 82.8 +/- 5.9), were recruited from seven homes and apartment houses for the elderly. QUS measurements (broadband ultrasound attenuation (BUA) and speed of sound (SOS)) were assessed with a clinical bone densitometer. A structured questionnaire was used to collect information on other potential predictors. Follow-up of fractures was done each half year by telephone interviews. During the study period (median follow-up 2.8 years, maximum 3.7 years), 30 participants had a first hip fracture and 54 suffered from a first other nonspinal fracture. Cox regression analyses, adjusted for age and sex, showed that the relative risk (RR) of hip fracture for each standard deviation reduction was 2.3 (95% CI, 1.4-3.7) for BUA and 1.6 (95% CI, 1.1-2.3) for SOS. Slightly weaker relationships were found for any fracture (BUA: RR, 1.6; 95% CI, 1.2-2.1; SOS: RR, 1.3; 95% CI, 1.0-1.6). Multivariable analyses identified low BUA values and immobility as the strongest predictors for hip fractures and any fracture. Female gender proved to be the strongest predictor for other nonspinal fractures. It can be concluded that QUS measurements can predict the risk for hip fracture and any fracture in elderly people.

The influence of physical activity and fractures on ultrasound parameters in elderly people.

In this cross-sectional study we investigated the relationship between ultrasound measurements in the calcaneus versus daily physical activity and fractures sustained in the past in elderly subjects. Ultrasound measurements were performed at both heels, which enabled us to examine determinants of differences between contralateral heels. Participants were 132 men and 578 women, aged 70 years and over (mean age and standard deviation (SD): 83 +/- 6 years), living in homes for the elderly (n = 343) or apartment houses for the elderly (n = 367). Broadband ultrasound attenuation (BUA) and speed of sound (SOS) were measured in the right and left calcaneus. The median difference (and interquartile range) between the two heels for BUA and SOS, expressed as a percentage of the mean value for each individual, was 9.6% (4.2-15.7%) and 1.0% (0.4-1.7%), corresponding to 25% and 40% of the study population SD, respectively. Greater differences in BUA between the two heels were associated with variables indicating poorer functional status, such as past fractures at the lower extremities. The level of daily physical activity was obtained by means of a questionnaire regarding household and leisure activities. Subsequently sumscores were calculated for daily physical activity and a subscore indicating weight-bearing physical activity. After adjustment for age, gender, residence, and body weight, physical activity scores were positively linearly related to both BUA and SOS. Each 5 point increase on the weight-bearing physical activity score, corresponding to, for example, walking for 2.5 h per week, was associated with a difference in BUA of 4.7 dB/MHz and in SOS of 5.1 m/s, which is similar to the differences associated with 10 kg higher body weight, or 10 years younger age. After the age of 50 years, 47 subjects had fractured a hip, 61 subjects had sustained another lower extremity fracture, 104 subjects a wrist fracture, and 62 subjects another upper extremity fracture. After adjusting for age, gender and residence, odds ratios for all fracture types in the lowest terciles of BUA and SOS versus the highest terciles ranged from 1.9 to 3.8. This study showed significant differences in ultrasound measurements between the left and the right heel, indicating that measurements at both sides are necessary for optimal evaluation of bone strength. Furthermore, after careful adjustments, ultrasound parameters had higher values with higher daily physical activity in elderly subjects and discriminated subjects with a history of fracture from those without.

The perinatal mortality rate as an indicator of quality of care in international comparisons.

The perinatal mortality rate is used as an indicator of the quality of antenatal and perinatal care, yet uncritical application of this indicator in international comparisons can be misleading. The perinatal mortality rate depends on a number of factors and important determinants that need to be assessed separately before reaching conclusions about quality-of-care issues. This article provides a conceptual model of the construction of the perinatal mortality rate. It illustrates the relationship between quality of antenatal and perinatal care and risk factors for perinatal mortality and how these lead to the perinatal mortality rate. It also indicates how differences in registration procedures and practices influence the final mortality figures published by individual countries. For international comparison, the first step is to apply common definitions. The rate can vary by 50% depending on the definition used. Also, sources of registration bias need to be examined, because they differ considerably by country. Underregistration is known to be as high as 20% of perinatal deaths. The next step is to correct perinatal mortality figures according to differences in known risk factors. The perinatal mortality rate then can serve as a reasonable indicator for the quality of antenatal and perinatal care. In western countries, perinatal mortality could be reduced by as much as 25% with improved standards of care. Policies and practices in individual countries concerning ethical issues related to termination of pregnancy and care of newborn infants with (very) poor prognosis need to be taken into account as well. They are not related to quality of care, but do have a relatively large impact on the perinatal mortality rate.

The effect of vitamin D supplementation on the bone mineral density of the femoral neck is associated with vitamin D receptor genotype.

Recent studies suggest that variations of the vitamin D receptor (VDR) gene are related to bone mineral density (BMD). In this study, we examined the effect of vitamin D3 supplementation on BMD at the femoral neck in relation to VDR genotype. We analyzed 81 women, age 70 years and over, who participated in a placebo-controlled clinical trial on the effect of vitamin D3 supplementation (400 IU daily for at least 2 years) on BMD and fracture incidence. VDR genotype was based on the presence (b) or absence (B) of the BsmI restriction site. Mean BMD of the right and left femoral neck was measured at baseline and after 1 and 2 years. Dietary calcium, body mass index, and years since menopause were assessed at baseline while biochemical markers were measured at baseline and after 1 year. There was no difference among the BB, Bb, and bb genotype for baseline measurements of BMD at the femoral neck (mean and SD, g/cm2: 0.70 (0.10), 0.71 (0.12), and 0.69 (0.10), respectively), nor for any of the biochemical indices. The mean increase of BMD in the vitamin D group relative to the placebo group, expressed as percentage of baseline BMD, was significantly higher (p = 0.03) in the BB (delta BMD: 4.4%, p = 0.04) and Bb genotype (delta BMD: 4.2%, p = 0.007) compared with the bb genotype (delta BMD: -0.3%, p = 0.61). No significant changes were found for any of the other measured parameters. The VDR genotype-dependent effect of vitamin D supplementation in these elderly subjects suggest a functional involvement of VDR gene variants in determining BMD.

An European concerted action investigating the validity of perinatal mortality as an outcome indicator for the quality of antenatal and perinatal care.

In this paper the concepts, objectives, design, and data analysis procedures of the EuroNatal study are described. This study started in 1996 and is a concerted action including 14 countries in Europe. The EuroNatal study aims at determining the validity of national perinatal mortality rates as an outcome indicator for the quality of antenatal and perinatal care. It is based on a conceptual model describing the relationships between differences in quality of antenatal and perinatal care, maternal and infant risk factors, variation in applied definitions, reliability of registration procedures and practices, and the outcome in terms of "true" and "observed" differences in perinatal mortality. In the first part of the study data is collected at national and aggregate level; in the second part data is collected retrospectively on individual cases of perinatal mortality in a regional sample area. Analysis of the individual cases of perinatal mortality will be by means of a perinatal audit conducted by an international expert panel. The project builds upon the work done by the participants in their respective countries. By applying common research protocols, international comparability of data collection will be enhanced and will help to create a common body of knowledge in the area of perinatal epidemiology and perinatal care. Comparison between countries is likely to lead to new insights into the strengths and weaknesses of antenatal and perinatal care systems of individual countries.

Ultrasound measurements in the calcaneus: precision and its relation with bone mineral density of the heel, hip, and lumbar spine.

Broadband ultrasound attenuation (BUA) and speed of sound (SOS) in the heel are suggested to measure bone density and structure and to predict fracture risk. Short-term precision (five consecutive measurements in 1 h) and long-term precision (six within 3 months) of ultrasound parameters were studied in 20 healthy subjects. The coefficient of variation (CV) did not change over a 3-month period for SOS (1.3%). Short-term precision of BUA was 3.4% (CV) and long-term precision was 4.9% (CV) (not significantly different: p = 0.09). Relationships between ultrasound parameters and BMD at various sites were examined in 42 subjects. BMD at the heel was assessed at the location corresponding to that of the ultrasound measurements (BMDheel). Correlation coefficients, corrected for imprecision in the measurements, for BUA and SOS vs. BMDheel, were 0.81 and 0.76, respectively. The correlation coefficients between heel measurements (BUA, SOS, and BMDheel) and BMD in the hip and lumbar spine ranged from 0.37 to 0.57. The relationships between BUA, SOS, and BMDheel vs. BMD of the hip were modified by physical activity and body weight. Higher physical activity and body weight were associated with higher BMD values at the hip. BUA values < 60 dB/MHz predicted BMD at the femoral neck < 0.70 g/cm2 with a sensitivity and specificity of 80% and 93%, respectively. After the age of 30, 11 participants had sustained vertebral fractures and 12 participants nonvertebral osteoporotic fractures. BUA and SOS values were significantly lower in fracture patients than in participants without fractures. It can be concluded that ultrasound measurements at the heel correlate well to BMD at the same site. BUA can predict BMD at the hip and is lower when the subject has sustained fractures.

Falls in the elderly: a prospective study of risk factors and risk profiles.

In this prospective study, the authors determined intrinsic risk factors for falls and recurrent falls and constructed a risk profile that indicated the relative contribution of each risk factor and also estimated the probabilities of falls and recurrent falls. In 1992, over a 28-week period, falls were recorded among 354 elderly subjects aged 70 years or over who were living in homes or apartments for the elderly in Amsterdam and the vicinity. During the study period, 251 falls were reported by 126 subjects (36%), and recurrent falls (> or =2 falls) were reported by 57 subjects (16%). Associations of falls and recurrent falls with potential risk factors were identified in logistic regression models. Mobility impairment regarding one or more of the tested items (i.e., impairment of balance, leg-extension strength, and gait) was associated with falls (adjusted odds ratio (OR) =2.6) and was strongly associated with recurrent falls (OR = 5.0). Dizziness upon standing was associated with falls (OR = 2.1) and recurrent falls (OR = 2.1). However, several risk factors were associated with recurrent falls only: history of stroke (OR = 3.4), poor mental state (OR = 2.4), and postural hypotension (OR = 2.0). The authors constructed a risk profile for recurrent falls that included the five risk factors mentioned above. Inclusion of all risk factors in the profile implied an 84% probability of recurrent falls over a period of 28 weeks, compared with 3% when no risk factor was present. The probability of recurrent falls ranged only from 11% to 29% when predicted by number of falls occurring in the previous year. Physical activity, use of high-risk medication, and the use of vitamin D3, which was randomly allocated to the participants, were not strongly related to either falls or recurrent falls. In conclusion, a large range of probabilities of falls, especially of recurrent falls, was estimated by the risk profiles, in which mobility impairment was the major risk factor. Recurrent fallers may therefore be especially amenable to prevention based on mobility improvement.

Vitamin D supplementation and fracture incidence in elderly persons. A randomized, placebo-controlled clinical trial.

OBJECTIVE: To determine whether vitamin D supplementation decreases the incidence of hip fractures and other peripheral bone fractures. DESIGN: Prospective, double-blind trial. SETTING: Community setting (Amsterdam and surrounding area). PATIENTS: 2578 persons (1916 women, 662 men) 70 years of age and older (mean age +/- SD, 80 +/- 6 years) living independently, in apartments for elderly persons, or in homes for elderly persons. INTERVENTION: Participants were randomly assigned to receive either vitamin D3, 400 IU in one tablet daily, or placebo for a maximum of 3.5 years. MEASUREMENTS: Dietary calcium intake and serum 25-hydroxyvitamin D [25(OH)D] were estimated in a subset of participants. During follow-up, attention was concentrated on hip fractures and other peripheral fractures. The maximal follow-up period was 4 years. The results were evaluated by survival analysis. RESULTS: Mean dietary calcium intake from dairy products was 868 mg/d. Mean serum 25(OH)D concentration in the third year of the study was 23 nmol/L in the placebo group and 60 nmol/L in the vitamin D group. Median follow-up was 3.5 years, and total follow-up was 8450 patient-years. During follow-up, 306 persons in the placebo group and 282 persons in the vitamin D group died (P = 0.20). Hip fractures occurred in 48 persons in the placebo group and 58 persons in the vitamin D group (P = 0.39, intention-to-treat analysis). Other peripheral fractures occurred in 74 persons in the placebo group and 77 persons in the vitamin D group (P = 0.86). CONCLUSION: Our results do not show a decrease in the incidence of hip fractures and other peripheral fractures in Dutch elderly persons after vitamin D supplementation.

Different risk profiles for hip fractures and distal forearm fractures: a prospective study.

In a prospective cohort of elderly persons, aged 70 years and over, we examined risk indicators for which data could be easily obtained, to construct risk profiles for hip fractures and distal forearm fractures. Participants lived independently, in apartment houses for the elderly or in homes for the elderly. At baseline, information was obtained in 2578 subjects on age, gender, residence, mobility and the frequency of going outdoors. Mobility was measured using a walking score ranging from 1 (not able to walk independently) to 3 (able to walk independently for a fair distance). During the study period (median duration 3.5 years, maximum 4 years) 106 participants sustained a hip fracture and 60 participants suffered a distal forearm fracture. Women compared with men, adjusted for age, had a higher risk of hip fracture (adjusted relative risk (RR) = 2.4, 95% confidence interval (CI) 1.3-4.3) and distal forearm fracture (RR = 3.7, 95% CI 1.5-9.2). Age, adjusted for gender, was related to hip fractures only: the relative risk of fracture for those in the highest age category (> 85 years) was 9.5 (95% CI 4.3-21.2) compared with those in the lowest age category (70-75 years). Moderately impaired walking ability compared with normal walking ability, adjusted for age and gender, was associated with a higher risk of hip fracture (RR = 1.8, 95% CI 1.2-2.7) but with a lower risk of distal forearm fracture (RR = 0.4, 95% CI 0.2-0.8). The outdoor score, adjusted for age and gender, was associated with distal forearm fractures only: going outdoors less than once a week, compared with three times or more, was associated with a lower risk of fractures (RR = 0.3, 95% CI 0.1-0.9). In those living in homes for the elderly the risk of hip fracture was higher compared with those living independently (RR = 2.4, 95% CI 1.4-4.2), adjusted for age and gender. Risk profiles were constructed using stepwise Cox's proportional-hazards regression. The risk profile predicted probabilities of sustaining a hip fracture in a 4-year period ranging from 0.4% to 25.9%, and of distal forearm fractures ranging from 0.2% to 4.5%, depending on the subject's characteristics as defined by the risk indicators. We conclude that easily obtainable risk indicators can be used in the prediction of fractures and can discriminate among fracture types.

Additional weight-bearing during exercise is more important than duration of exercise for anabolic stimulus of bone: a study of running exercise in female rats.

Mechanical loading is necessary for maintenance of skeletal integrity, but the most effective type, intensity, and duration of exercise are not known. In vivo experiments have indicated that the strain generated by the stimulus is more important than the duration of the stimulus. To elucidate this question, we studied 5-month-old female Wistar rats exercised on a motor-driven exercise belt for 17 weeks, 5 days per week (average velocity 20 m/min). Group 1 served as controls, group 2 was trained for 30 min, group 3 was trained for 30 min with a 50-g backpack, and group 4 was trained for 15 min with a 50-g backpack. Total body bone mineral content (BMC), bone mass of the lower extremities (LEBMC), total body lean soft-tissue mass (LSTM), and total body fat-tissue mass (FTM) were measured by dual-energy absorptiometry (DXA) at 0, 6, and 17 weeks. The BMC increased more in group 4 than in controls (15% vs. 8%, p < 0.03). In the other two intervention groups, no significant increases of total body BMC occurred compared with controls, although a trend was observed (12%). The LEBMC increased significantly in all exercising groups after 17 weeks, being 16% in group 2, 15% in group 3, and 20% in group 4, compared with 6% in controls (p < 0.05). The increase in LSTM after 6 weeks was most pronounced in group 3, at 20%, compared with 10% in the control group (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)