This multicenter study showed that by applying a simple risk assessment instrument at admission, three subgroups of older patients with distinct clinical characteristics and outcomes could be identified. Twenty-seven percent of the patients were at low risk for functional decline, 33% were at intermediate risk and 40% were at high risk for developing new disabilities. Patients at high risk for further functional decline presented with the highest number of geriatric conditions. High-risk patients were also at the highest risk for poor outcomes in terms of mortality and deterioration in ADL functioning and their mean overall decline in functioning was significantly greater.
The low-risk group, as expected, presented with the fewest geriatric conditions and ADL impairments at admission but still had an average of two geriatric conditions besides the acute and chronic diseases leading to hospital admission. The number of geriatric conditions and premorbid ADL impairments gradually increased in the intermediate- and high-risk groups. The findings on the differences between the subgroups are consistent with other studies that used a more detailed risk classification for functional decline or frailty 
The geriatric conditions most often present in the high-risk group (cognitive impairment, delirium, premorbid ADL impairment, urine incontinence and fall risk) reflect the patients' frailty 
and are known risk factors for future functional decline 
. The high-risk group presented with the most baseline impairments and the greatest deterioration of ADLs both in percentage and the mean number of decline over the follow-up period. Lost functions are difficult to recover, and new disabilities or impairment reported at discharge that are still present at one month of follow-up are especially difficult to rehabilitate 
. Patients discharged with new or additional disabilities also have the highest probability of dying in the year after admission 
. The severity of the acute illness leading to admission is an important risk factor for mortality 
. This risk factor might explain the still relatively high mortality rates of 27% and 30% in the low- and intermediate-risk groups, respectively, up to one year after admission.
Compared with the low-risk group, the intermediate group showed an increased risk for functional decline at three months, but this increased risk disappeared at one year. A clear association between the high-risk group and mortality and functional decline was demonstrated at both time points. Only one-third of this group maintained baseline function one year after admission. This finding could indicate that the intermediate group has more potential for further rehabilitation after admission compared with the high-risk group, which might be too frail. Research has demonstrated that once patients begin to decline, they are more prone to further decline, even if they have regained their initial level of functioning 
. More interestingly, one large study on functional decline at the end of life clearly demonstrated that functional trajectories for patients with both organ failure and frailty in the last year of life demonstrated an almost continuous decline in ADL functioning, starting with already many baseline impairments, whereas in patients with end-stage cancer, this decline only starts in the last two or three months of life and these patients predominantly have a good level of ADL functioning 
. In our study this might also be visible; in the low risk group, many patients died, but did not have much premorbid dependencies. These patients were more frequently cancer patients, whereas in the high risk group, many baseline impairments were present, and these patients demonstrated most decline in the year after hospital admission.
An important question is whether risk status can identify the patients most likely to benefit from multidisciplinary intervention by a geriatric consultation team. Results of a meta analysis of inpatient geriatric rehabilitation argued that subgroup evidence in favor of providing geriatric rehabilitation during and after hospital admission is warranted 
and that more tailored approaches to patient selection still need to be tested. A recent randomized clinical trial (RCT) focusing on disease management in older heart failure patients divided participants into three risk groups and found that there was a difference in intervention benefits, in terms of both outcomes and costs, in favor of the intermediate-risk group 
. The authors argued that the low-risk group was too healthy and that the high-risk group too ill to profit from the intervention.
Further research should focus on testing this risk-based approach in acutely hospitalized older patients. This research could be implemented in two ways. The first is an impact study, testing the clinical usefulness of the approach by determining whether the risk assessment outcomes influence decision making and goal setting in both physicians and patients 
. The second study that could be performed is an RCT using the three risk groups as a basis for goal setting and intervention. The ICF rehabilitation model could inform goals for the low-, intermediate- and high-risk groups 
. The ICF rehabilitation model identifies several different health strategies, which can be used to determine rehabilitation outcomes. The three health strategies that might be relevant in relation to this study are the preventive health strategy, in which the main purpose is to prevent health conditions and remain functioning. The second strategy is aimed at rehabilitation in which the primary goal should be to restore functioning and the third strategy is supportive care direct towards maintaining quality of life and preservation of autonomy. These strategies might be relevant for the low, intermediate and high risk group, respectively.
Some limitations need to be addressed. First, in our study, we made a predefined selection with one risk assessment instrument, the ISAR-HP. Our main purpose was to demonstrate that a risk assessment instrument can be helpful to detect low-, intermediate- and high-risk patients. Although our study is a multicenter study, using the ISAR-HP for this purpose in other settings might produce different arising from differences in the case mix of patients, leading to a different distribution of the outcome and predictive factors 
. We clearly demonstrated that this risk-based approach revealed differences in baseline (clinical) characteristics and health outcomes, further enhancing the validity of this screening instrument.
Second, functional decline was operationalized as a one-point decline at follow-up functioning compared with premorbid functioning. For further analyses, we dichotomized the outcome as present or absent. Although this approach is used in most studies of functional decline in hospitalized older patients 
, it leads to a loss of information about the ADL functioning level after hospitalization.
Third, the inclusion percentage was 62%. This expected but still low inclusion rate is a common problem in studies of acutely hospitalized older patients, and most trials conducted in this population demonstrated equal or lower participation rates 
. We did conduct a small non-respondent analysis in which we demonstrated that the patients that were excluded were often younger and died more frequently after discharge. Presumably, these patients more frequently had end stage diseases or were very frail older patients. It would have strengthened the validity of study results, if we would have collected more baseline information on these patients.
In conclusion, by using an easily applied risk assessment instrument at hospital admission, three patients groups (low, intermediate and high risk for functional decline) with distinct clinical characteristics could be distinguished. This approach might contribute to better defining of treatment goals at hospital admission, earlier initiation of appropriate (preventive) interventions and better communication with patients and caregivers about the preferred outcomes of admission. The application of this approach and the effectiveness of risk-based clinical interventions should further be tested in clinical practice and randomized clinical trials.