Complementarity of the Mini-Nutritional Assessment (MNA) and Activities of Daily Living (ADL) for predicting follow-up mortality risk in elderly Taiwanese
Alan C. Tsai,1,2,* Li-chin Lee1,3 and Jiun-Yi Wang1
1Department of Healthcare Administration, Asia University, Taichung 41354, Taiwan 2Department of Health Services Management, School of Public Health, China Medical University, Taichung 404, Taiwan
3Center of Administration, Tungs' Taichung MetroHarbor Hospital, Wuchi, Taichung, 43503, Taiwan
*Address all correspondence to: Alan C. Tsai, Ph. D., Professor
Department of Healthcare Administration, Asia University 500 Liufeng Rd., Wufeng, Taichung 41354, Taiwan Phone: 886-4-2332 3456 x1943; Fax: 886-4-2332-1206 e-mail: [email protected]
Keywords: Mini Nutritional Assessment (MNA); Activities of Daily Living (ADL); Mortality; Functional status; Elderly
Short title: MNA and ADL for predicting mortality risk 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
Abstract
Physical functional ability and nutritional status are two major indicators for predicting the risk of mortality in older adults. This study examined the complementarity of the Activities of Daily Living (ADL) and the Mini-Nutritional Assessment (MNA) for predicting follow-up four-year all-cause mortality risk in elderly Taiwanese. We analyzed data of the “Survey of Health and Living Status of the Elderly in Taiwan” (SHLSET), a population-based longitudinal cohort study which involved 2872 ≥65 years old men and women at baseline (1999). We rated their functional dependency with the ADL scale and nutritional status with the MNA (both the long-form, LF and the short-form, SF) at baseline, and analyzed the complementarity of the two scales in predicting follow-up four-year all cause mortality with Cox regression analysis and Net Reclassification Improvement (NRI) to quantify the improvement. Results showed that the ADL and the MNA both offered improvement in predicting follow-up mortality risk beyond that predicted by either one alone according to Akaike Information Criterion (AIC) and NRI. The MNA-SF was nearly as effective as the MNA-LF in improving the predictive ability of the ADL. The study suggests that the MNA (especially the SF because of its simplicity and time-saving feature) together with ADL scale might be of value for predicting mortality risk of frail elderly living in most settings.
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Introduction
Physical functional ability and nutritional status are two major indicators for predicting mortality in older adults. Decline in functional status is a profound predictor of mortality(1). The death rate increases from 8% in individuals with no disability, to 15% with one or more IADL (Instrumental Activities of Daily Living) disabilities, to 21% in persons with one or two ADL (Activities of Daily Living) dependencies, and up to 37% in those with five or six ADL dependencies during a two-year period(2). On the other hand, nutritional status is also a strong predictor of mortality. Numerous studies have shown that death rate is much higher for elderly who are malnourished than those who are well nourished(3-7). In a recent study, we have shown that the relative mortality risk is about 7 times for individuals who are malnourished and 2.5 times for those who are at risk of malnutrition compared to those who are normal when rated with the MNA (Mini-Nutritional Assessment)(8). The two indicators have been shown to be highly correlated, but the complementary effect between the two has not been well studied. Hence, the study was aimed to determine the extent by which the two tools (functional status and nutritional assessment) together can improve the ability to identify those who otherwise would not be identified by either one alone.
Methods
Data and Subjects
The study analyzed datasets of the “Survey of Health and Living Status of the Elderly in Taiwan” (SHLSET), a population-based longitudinal cohort study conducted by the Bureau of Health Promotion of Taiwan. The goal of the survey was to gain an understanding of the role of demographic, socioeconomic, environmental, lifestyle, and healthcare factors on health, well-being, and quality of life of older Taiwanese(9). SHLSET employed a three-stage national probability sampling method. Stage one stratified the Taiwanese population into 361 primary sampling units (PSU) and (after excluding 30 lightly populated mountainous PSUs) randomly selected 56 PSUs for further sampling. Stage 2 was a proportional-to-size random selection of blocks from the selected PSUs and the final stage was a random selection of two eligible persons from each of the selected blocks. A total of 4412 men and women aged 60 years or older were drawn with this process and among them, 4049 completed the first interview in 1989. A second sample of 2462 subjects, 50-66 years old, was drawn from the population with the same
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procedure in 1996 to maintain/extend the age of cohort. Subjects in the combined cohort were interviewed with a structured questionnaire for eliciting demographic, socioeconomic, lifestyle and health or healthcare-related data every 3 or 4 years (in 1989, 1993, 1996, 1999, 2003 and 2007). The completion rates ranged from 79.1% to 91.8%. The 1999 survey had a special emphasis on diet and nutrition and the questionnaire included most items in the MNA, meeting the need of the present study and thus was chosen as baseline of this analysis. The method and procedure was reviewed and approved by government-appointed representatives. The detailed sampling process of the survey has been described previously(10). This study was conducted according to the guidelines laid down in the Declaration of Helsinki and all procedures involving human subjects were approved by the ethics committee. Written informed consent was obtained from all subjects.
The Mini-Nutritional Assessment (MNA)
We graded the nutritional status of each subject with both the long-form (LF) and short-form (SF) of the MNA which is well recognized as a simple, easy-to-use, reliable, and non-invasive tool for screening/assessing the risk of malnutrition in older adults. The MNA is a two-part and two-stage scale. The LF includes 18 items and evaluates four aspects of nutritional status (dietary, anthropometric, global, and self-view)(11). Elderly suspected of malnutrition are first screened with the SF consisting of 6 key questions. Those who are rated as at risk of malnutrition are further evaluated with the rest of the LF (additional 12 questions) to complete the diagnosis(12). Under most conditions the SF predicts the LF well and can function
independently as a screening tool.
Measurements
Because of population-related differences, we rated the nutritional status of subjects in the present study with a slightly modified version (Taiwan version-2, T2) of the MNA. MNA-T2 adopted the Taiwanese-specific anthropometric cut-off points(13) and also replaced item R (calf-circumference) for item F (Body Mass Index, BMI)(14). MNA-T2 has been shown to perform better or at least equal to MNA-T1 (a normalized version by adopting population-specific anthropometric cut-off points). Data for all items in MNA-LF, except items I (pressure sore/skin ulcers) and M (fluid intake) were available in the survey database. So, the MNA was based on 15 items with a maximum score of 28 points, rather than 17 items for 30 points. However, the total score was proportionately adjusted to the full score basis. A final score of ≤16.5 suggests 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105
malnourishment; 17-23.5, at risk of malnutrition; and 24 or more, normal. All MNA-SF items were available in the questionnaire. MNA-SF has a maximum score of 14. A score of 0-7 indicates malnourished; 8-11, at risk of malnutrition and 12-14, normal(12).
Functional status was assessed using a self-report questionnaire containing the ADL adapted from the 1984 National Health Interview Survey Supplement on Aging(15). Two types of scores could be derived from the scale. One measured difficulty in carrying out the items (the method used in the present study) and the other measured the degree of difficulty in performing each of the six items (bathing, dressing, transferring, eating, walking, or toileting). An item that one "cannot do independently" is considered "dependent" for that item. The number of items that one "cannot do" was then totaled(16). Mortality data were obtained from records maintained by the SHLSET project and confirmed with records of the Universal Health Insurance Program and the National Household Registration.
Statistical analysis
Subjects' baseline characteristics, nutritional status, number of ADL dependency and follow-up four-year mortality were computed with simple statistics. We used Cox regression analysis (with Akaike Information Criterion, AIC) and Net Reclassification Improvement (NRI) (17) to quantify the improvement offered by the two markers, the MNA and the ADL, in
predicting follow-up four-year all-cause mortality. In Cox regression analysis, we calculated the lengths of survival time for subjects who died during the follow-up 4 years according to records maintained by the SHLSET project and took 48 months as the censoring time for subjects who survived, and we used the changes in AIC values to indicate the improvement in predictive abilities. In an adaptation (18) of NRI analysis (17), we computed the differences in proportions of upward and downward reclassifications in the fatality groups minus the differences in
proportions of upward and downward reclassifications in the survivor groups after the inclusion of the MNA ratings to ADL ratings (17). We considered number of ADL dependencies (0, 1-2, or ≥3) to be the base risk, whereas the augmented risk function was the combination of number of dependencies with the MNA ratings. For each ADL stratum, we defined upward
reclassification as nutritional status worse than normal (at higher risk) and downward as normal nutritional status (at lower risk). All statistical analyses were performed with SAS statistical software package (SAS Institute, Inc., Cary, NC, USA). Statistical significance for all analyses was accepted at α = 0.05. 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136
Results
Table 1 shows the characteristics of subjects. The sample included slightly more men which reflected the composition of the age group. More than half (64.9%) of subjects were 65-74 years of age and the rest were over 75 years; only 21.4% of subjects had more than 6 years of formal education; 11% lived alone; 25% were current smokers; 14% drank once or more per week and 55% exercised more than 3 times per week.
Table 2 shows the classification of ADL status and the follow-up four-year mortality according to the nutritional status rated at baseline. The MNA-LF rated 2.7% as malnourished, 12.7% as at risk and 84.6% as normal while MNA-SF rated 3.5 %, 19.0%, and 77.5%,
respectively. Greater proportions of subjects who were malnourished or at risk of malnutrition had higher numbers of ADL dependency. Applying the MNA and ADL ratings simultaneously identified additional elderly with increased follow-up four-year mortality risk who would otherwise be missed by either scale alone. Compared to the MNA-LF, the MNA-SF showed relatively good ability in predicting follow-up four-year mortality risk.
Table 3 shows that both MNA (both forms) and ADL presented significant independent mortality-predictive abilities and complemented each other in predicting follow-up four-year mortality risk (all p<0.001). It also exhibits the improvement in predicting the follow-up
mortality according to the changes in AIC values by adding the nutritional status and/or the ADL status to the models. The MNA-LF showed greater improvement than the MNA-SF.
Table 4 shows the cross-classification according to ADL and MNA ratings for subjects who died and for those who survived during the follow-up four years. Among those who died, 205 subjects were reclassified in a higher risk and 374 in a lower risk by the MNA-LF; among those who survived, 238 subjects were reclassified in a higher risk and 2055 in a lower risk. The unstratified NRI was estimated to be 0.51 (p<0.001), which suggested a significant improvement after inclusion of MNA-LF. The MNA-SF showed comparable improvement (the unstratified NRI = 0.53, p<0.001). The stratified NRIs after inclusion of MNA-LF were 0.33 (SE 0.042, p<0.001), 0.24 (SE 0.254, p = 0.355) and 0.05 (SE 0.193, p = 0.790) for 0, 1-2 and ≥3 ADL dependencies, respectively. The MNA-LF improved mortality prediction of ADL alone for those with 0, but not for those with 1-2 or ≥3 dependencies. The stratified NRIs after inclusion of MNA-SF were 0.38 (SE 0.047, p<0.001), 0.28 (SE 0.255, p = 0.260) and 0.08 (SE 0.191, p = 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167
0.688), similar to that observed with the MNA-LF.The stratified NRI shows that most of the improvement in classification over ADL alone arises within the people with 0 dependency, and little or no improvement in classification occurs in the people with ≥3 dependencies.
Table 5 shows the cross classification of results rated with the MNA-SF vs. that rated with the MNA-LF. Among 101 elderly rated as malnourished by the SF, 39 were rated as at risk by the LF; among 545 rated as at risk by the SF, 16 were rated as malnourished and 241 as normal by the LF; and among 2226 rated as normal by the SF, 38 were rated as at risk by the MNA-LF.
The follow-up four-year Cox regression curves stratified by the number of ADL
dependency and nutritional status (rated with MNA-LF and MNA-SF, respectively) adjusted for sociodemographic (age, sex and education), lifestyle (smoking, drinking and exercise), and health (hypertension, heart disease, diabetes, stroke and cancer) variables are shown in Fig. 1. The impact on follow-up four-year survival by malnutrition and functional decline reached statistical significance (p<0.05) in most cases.
Discussion
Predicting mortality
Healthcare providers often rely heavily on measures of functional status such as ADL to get an idea of the risk of mortality in frail elderly. But that approach may miss a significant proportion of the vulnerable individuals. Assessing nutritional status (with the MNA) in addition to measuring physical functional status (ADL) may add useful information. Our results suggest that measuring both ADL and nutritional status provides a more accurate indication of mortality risk than assessing either one alone. When ADL status and the risk of malnutrition of general older adults are both graded into three levels and calculate the relative mortality risk, people who are malnourished have markedly elevated risk of mortality in individuals seemingly functionally independent (those without any dependency). Subjects who had greater number of ADL
dependencies and poorer nutritional status were associated with the greater follow-up mortality risk. These results suggest that the MNA can improve the ability of ADL to predict follow-up mortality risk in frail elderly.
The MNA has long been shown to predict the risk of mortality of elderly living in various settings. van Nes et al.(19) observed that elderly hospital in-patients with poor nutritional status as 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198
rated with the MNA was associated with a longer length of stay and increased in-hospital mortality. Similarly, Donini et al.(5) observed that a low MNA score was predictive of greater incidence of adverse clinical events during hospitalization and of higher follow-up mortality in elderly patients. Beck et al.(3) found that an MNA score ≤23.5 points predicted mortality risk in a group of 70–75-year-old Danish population. In a prospective follow-up study, Persson et al.(4) observed that the MNA was able to predict 3-year follow-up mortality risk in geriatric patients.
The MNA is a multidimensional and multifunctional scale. Both the LF and the SF scales evaluate multi-aspects of nutritional health. The MNA has been shown to have the ability to predict functional status, hospital cost and mortality risk, in addition to nutritional status(20-24). Thus, it is not surprising that the MNA can enhance the ADL in predicting the risk of mortality in the elderly.
Our regression models suggest that nutritional status and ADL dependency are two major independent predictors of follow-up mortality risk in elderly persons. The models also show that the MNA-SF is comparable to the MNA-LF in improving the ability of ADL in predicting the follow-up mortality risk. Because the SF is much simpler and time-saving to administer than the LF, it is often much more desired in routine practice. Although the MNA-LF is stronger than the MNA-SF in predicting nutritional risk, the SF appears as effective as the LF in predicting follow-up mortality risk.
Results also show that among 101 rated as "malnourished" by MNA-SF; the MNA-LF "clarifies" that 39 of these (39%) are actually at lesser risk (at risk). Among the 545 rated as "at risk" by the MNA-SF, almost half (241) are relabeled as "normal". Thus, among those in whom any action should be taken, the LF shows that a lesser action would suffice in 280/646, or 43%. Changes to a diagnosed greater risk state are less frequent, only 54 people. Thus the MNA-SF has a great deal of similar signal to the MNA-LF, but certain classifications are different in many people. Whether this matters depends on the cost of further diagnosis or intervention action. The 241 who are rated as at risk by the MNA-SF but as normal by the MNA-LF are probably those who are having emerging nutritional problems.
The complementarity can also be demonstrated by adding the ADL classifications to the MNA classifications (Appendix A). With any dependency taken as upward reclassification and no dependency taken as downward reclassification, the unstratified NRI is 0.34 (SE 0.033, p<0.001), while the stratified NRIs are 0.12 (SE 0.027, p<0.001) for those who are rated as 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229
normal by the MNA-LF, 0.35 (SE 0.087, p<0.001) for those who are rated as at risk, and 1.10 (SE 0.211, p<0.001) for those who are rated as malnourished. Similar results are obtained by adding the ADL classifications to MNA-SF classifications. Thus, addition of ADL classifications information to MNA classifications leads to significant reclassification improvement,
particularly in the malnourished subgroup.
Strengths and limitations
A major strength of the study is that the data were from a longitudinal cohort study involving a relatively large population-representative sample. The baseline physical functional (ADL) and nutritional (MNA) status can infer causal relationship with the follow-up mortality risk. However, there are also limitations. (a) Despite relatively large sample size, when classified by ADL and nutritional status simultaneously, the number of observation is relatively small in some cells. (b) Most data were obtained through interviews. In persons who were cognitively impaired, data were mostly obtained through proxies. The quality of such data might be compromised. (c) No biochemical data were available in the datasets to support our current findings. Thus, confirmation the nutritional status graded with the MNA with biomarkers is not possible.
Conclusion
Using Cox regression and NRI, we have conclusively shown that nutritional (MNA) and functional (ADL) ratings complement each other in predicting the follow-up four-year mortality risk in the elderly. Rating the elderly with both tools simultaneously can provide a more accurate prediction of mortality risk than with either one alone. The MNA and ADL are two simple and non-invasive scales that can be easily administered to elderly living in almost any setting. Simultaneous application of the MNA and ADL appears to be an effective and economical way of identifying those elderly who are in need of intervention.
Acknowledgments
The authors thank the David Jacobs, PhD, for contributions concerning the use of NRI in this paper. This study is based on the data from the “Survey of Health and Living Status of the Elderly in Taiwan” (SHLSET), provided by the Bureau of Health Promotion, Department of Health, R.O.C (Taiwan). Descriptions or conclusions herein do not represent the viewpoint of the 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260
Bureau. The authors declare that they have no competing interests. ACT conceived the idea and directed the study, and is the main writer of the manuscript. LCL and JYW performed the statistical analysis and reviewed the manuscript.
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(Legends for Fig. 1)
Fig. 1. Cox regression analyses of the follow-up four-year survival curves stratified by number of ADL dependency and nutritional status (rated with MNA-LF and MNA-SF, respectively)
adjusted for demographic (age, sex and education), lifestyle (smoking, drinking and exercise), and health-related (hypertension, heart disease, diabetes, stroke and cancer) variables. Sets of data in each panel are hazard ratios and 95% confidence intervals for 1-2 dependencies (HR1) and ≥3 dependencies (HR2) using the "ADL-intact" group as the referent. In the Cox regression analysis, lengths of survival time were calculated according to the records maintained by the SHLSET project for subjects who died during the follow-up four years, and taken 48 months as the censoring time for subjects who survived.
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