The European Journal of Public Health Advance Access published online on June 1, 2008
The European Journal of Public Health, doi:10.1093/eurpub/ckn020
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Predictive items of functional decline and 2-year mortality in nonagenarians—the NonaSantfeliu study
Assumpta Ferrer1, Francesc Formiga2, Domingo Ruiz3, Jordi Mascaró2, Claudia Olmedo1 and Ramón Pujol2
1 Geriatric Unit, Internal Medicine Service, Hospital Universitari de Bellvitge, L’Hospitalet de Llobregat, Barcelona, Spain
2 Primary Health Care Centre "El Plà" CAP -I, Sant Feliu de Llobregat. Barcelona, Spain
3 Geriatric Unit, Internal Medicine Service, Hospital Sant Pau, Barcelona, Spain
Correspondence: Francesc Formiga, MD, Geriatric Unit, Internal Medicine Service, Hospital Universitari de Bellvitge, L’Hospitalet de Llobregat 08907, Barcelona, Spain. tel: +34 93 260 74 19, fax: +34 93 260 74 20, e-mail: fformiga{at}csub.scs.es
Received May 16, 2007, accepted March 12, 2008
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Abstract |
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Background: Few studies have prospectively evaluated predictors of mortality or decline in functional capacity in nonagenarians. The aim of this study is to determine predictors of death or functional decline in basic activities of daily living in nonagenarians after 2 years of follow-up.
Methods: One hundred and seventy-six nonagenarians were prospectively evaluated. Functional status was determined by the Lawton–Brody index (LI) and the Barthel Index (BI), and cognition by the Spanish version of the Mental State Examination. The Charlson score was used to measure co-morbidity. Nutritional status was evaluated by the short version of the Mini Nutritional Assessment questionnaire. Results: The sample comprised 135 women (76.3%) and 41 men. Mean age was 93 ± 3.2 years. Mortality after 2 years was 36.3%. Forty-six (41%) of the 112 survivors presented BI losses >19%. One hundred and ten subjects (63%) presented the combined negative outcome item (death or functional decline). A multiple stepwise logistic regression analysis identified two variables associated with a fall of >19% on the BI or death: a low LI (odds ratio 0.785, 95% CI 0.656–0.940) and a low score at baseline on the Spanish version of the Mental State Examination (odds ratio 0.950, 95% CI 0.914–0.987).
Conclusion: Better cognitive status and higher capacity to perform instrumental activities of daily living (ADL) at baseline are the best predictors to identify which nonagenarians survived without major functional decline after a 2-year follow-up period.
Keywords: functional decline, mortality, nonagenarian, physical performance
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Introduction |
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Increasing longevity of the population induces an increasing in multi-morbidity rates. Most studies of the oldest old in nonagenarian samples in our geographical area have shown a predominance of women, usually widows, many of whom have maintained functional independence.1,2 Male nonagenarians with low co-morbidity probably undergo more successful aging than females or than nonagenarians with high co-morbidity.3–5
In an earlier study in our area we found a mortality rate of 28.5% after 1 year of follow-up in a cohort of 182 nonagenarians hospitalized because of health problem (medical, surgical or orthopedic admission).1 More recently, in the first year of a follow-up study of the NonaSantfeliu cohort we found a mortality rate of 19.3%.6 Few studies have prospectively evaluated predictors of mortality in nonagenarians.7,8 The previous results of the Danish 1905-cohort survey reported that in the oldest old, several known predictors of mortality, such as sociodemographic factors, have lost their importance, but high disability level, poor physical and cognitive performance and self-related health (women only) predict mortality.7
Apart from mortality, an important health measurement in elderly people is functional status. The proportion of subjects with functional dependence in activities of daily living (ADL) increases with age.9 Extensive literature has evaluated the predictors of functional decline (age, cognitive status, etc) in samples of elderly people. However, few studies have prospectively evaluated predictors of loss of functionality in nonagenarian cohorts.2
Since it is important for elderly people to live with the highest possible level of independence, we decided to assess these two items in a 24-month study determining the contributions of a combined item termed ‘negative outcome’, consisting of total mortality or functional decline. We evaluated several measurements of physical and cognitive function, and clinical and sociodemographic characteristics in a cohort of non-selected nonagenarians. The aim of this study is to determine predictors of death or functional decline in basic activities of daily living in this group of oldest old. We have hypothesized that known predictors of mortality or functional decline in younger elderly lose their importance in oldest old when both items were evaluated together.
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Methods |
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The data were taken from the NonaSantfeliu study, a population-based study of nonageznarian inhabitants in the town of Sant Feliu de Llobregat (Barcelona, Catalonia, Spain). The survey has been described in detail elsewhere.2,3,6 In brief, all 305 nonagenarian residents were contacted. Sixty-one per cent replied (n = 186 participants). There were no exclusions due to health criteria, cognition or dwelling status (i.e. community or institutionalized). The population of Spanish nonagenarians is predominantly Caucasian and is ethnically homogenous. After 24 months, assessment could not be performed in 10 participants who changed residence or were lost at the time of follow-up.
The institutional ethics committee of the ‘Fundació Jordi Gol i Gurina per a la Recerca a l’Atenció Primària de Salut’ approved the study. All patients, or the carers of cognitively impaired subjects, gave their written informed consent prior to enrolment. The participants were interviewed at their home, rest home or health centre by a geriatric-trained research team. A proxy-responder was encouraged to participate in the interview if the nonagenarian was unable to participate due to mental or physical handicap. Geriatric assessment and sociodemographic data (gender, marital status, place of residence and educational level) were recorded.
Geriatric global assessment
The usual current tools were used for the assessment of functional status, cognitive status and nutritional status in our subjects. Functional status was measured using the Barthel Index (BI)10 for basic ADL (BADL), and the Lawton and Brody Index (LI)11 for instrumental ADL (IADL). The total score of the BI ranges from 0 to 100 points (from ‘help needed’ to ‘independent in all activities’), and the LI scale ranges from 0 to 8 points (8 meaning that no help is needed). Cognitive function was measured by the Spanish version of the Mini-Mental State Examination (MEC),12 with a score up to 35 (scores below 24 indicate cognitive impairment). Nutritional risk was evaluated by the short version of the Mini Nutritional Assessment questionnaire (short-MNA).13 This includes six items from the MNA (body mass index, appetite, weight loss, mobility, current illness and neuropsychological problems). The height and weight data used for the analysis of body mass index were self-reported. Scores range from 0 to 14 points, scores below 11 denoting patients at risk of or suffering from protein-energy malnutrition.
Sensorial status
Shortsightedness was measured with Snellen charts. A score below 20/40 at 40 cm, with the best eye, wearing glasses was considered abnormal. Hearing ability was measured by the Whisper test, with the examiner sitting 60 cm behind the subject, so that he/she could not read the examiner's lips.14 Failure on this test is equivalent to a hearing loss of more than 30 decibels in audiometric studies. Subjects’ hearing was classified as intact or deteriorated.
Co-morbidity and cardiovascular risk factors
The Charlson co-morbidity Index was used to measure overall co-morbidity.15 The score ranges from 0 to a theoretical maximum of 33, depending on the presence of certain diseases with assigned values. Our investigation placed special emphasis on the presence of diagnoses of hypertension, diabetes, dyslipidaemia, ischaemic cardiopathy, heart failure, chronic obstructive pulmonary disease (COPD), dementia, presence of previous stroke and chronic drug prescription.
Overall mortality and functional decline at 1 year of follow-up
Vital status for the total cohort was evaluated. Individuals were followed up for 24 months or until they died, whichever occurred first. In the patients who survived BI was recorded. Decline in functional status was considered significant when the BI had fallen >19% in the last 2 years. Patients who died or had a BI loss of >19% were compared with the rest.
Statistical analyses
Normally distributed continuous variables are reported as means ± standard deviation. Categorical variables are reported as proportions. Student's t-test was used to compare continuous normally distributed variables, and the chi-square statistic or Fisher's exact test was used for the comparison of categorical or dichotomous variables. Age, gender and the covariates shown to be significantly associated with death or BI loss of >19% were then explored by means of a multiple logistic regression analysis, adjusted odds ratio (OR) with 95% confidence interval (CI) were used. The results were considered significant when P < 0.05. SPSS 11.0 statistical software (SPSS Inc, Chicago, III) was used to perform the analyses.
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Results |
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One hundred and seventy-six nonagenarians were finally evaluated. The sample comprised 135 (76.3%) women and 41 men, with a mean age of 93 ± 3.2 years at baseline. 79.5% were widowed, 9.73% married and 11.42% unmarried. Most lived in community-based housing (72.3%) and the remaining 27.1% were institutionalized. As regards educational level, 1.1% had a university degree, 6.82% had reached high school, 67.2% had completed primary school and 24.3% had received no basic education.
Geriatric assessment
The mean values of geriatric assessment scales at the beginning of the follow-up study period were: LI 2.1 ± 2.2; BI 60.8 ± 30; MEC 21 ± 11; MNA-SF 11.1 ± 2.4.
Twenty-six per cent had a previous diagnosis of dementia, 38.6% had auditory impairment and 39.8% had visual impairment.
Co-morbidity evaluation and cardiovascular risk factors
The mean score of the Charlson Index was 1.4 ± 1.7. Hypertension was found in 59.7% of subjects, diabetes in 16.6% and dyslipidaemia in 18.1%. Previous clinical history of ischaemic cardiopathy (11.9%), heart failure (26.1%), COPD (15.3%) and stroke (19.3%) were recorded. Patients were taking an average of 4.3 ± (2.5) drugs; 134 patients (76.1%) were on treatment with three or more drugs.
Evaluation after 2 years’ follow-up
Sixty-four patients died during the 24 months of follow-up period (36.3%). Thirty-six patients (20.4%) died during the first 12 months.
After a 24-month follow-up the mean BI score of the 112 survivors had fallen from 68.6 to 57.4; this 11-point change was statistically significant (P < 0.004). Forty-six of the 112 survivors (41%) had a BI loss >19%.
Predictors of mortality or loss of BI >19%
The combined item of negative outcome (death or functional decline >19% of BI at baseline) was recorded in 110 subjects (63%) presented. Table 1 shows the differences between the two cohorts. Multiple stepwise logistic regression analysis identified two variables (LI and MEC) associated with a BI fall of more than 19 points or death (table 2). In this way, better cognitive status and higher capacity to perform instrumental ADL at baseline predicts which nonagenarians survived without major functional decline at 2-year follow-up.
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Discussion |
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Nonagenarians represent one of the fastest growing population groups in developed countries. Establishing an accurate prognosis for a vulnerable population such as nonagenarians is clearly useful for public health policy. In order to identify the factors that may have contributed to survive without major functional decline, we explored a combined item of 2-year mortality and a major loss in basic ADL in a 24-month follow-up study. Only 37% of nonagenarians evaluated were alive and without significant functional decline at the end of the study. In the rest, a negative event occurred. In the present study poor instrumental performance and poor cognitive status were significant predictors of the combined item of functional decline or death in the nonagenarians after 2 years of follow-up.
It seems that the exponential relationship between age and morbidity recorded in subjects aged 65–84 years does not apply to nonagenarians. At this age, the mortality rates and indicators of morbidity are considerably lower than expected.16 In a previous study evaluating Danish nonagenarians, 6 month overall mortality was found to be between 7.2% and 11.8%,17 rising to 25.7% after 15 months.7 When longer periods were evaluated, the proportion of deaths reached 60%, as reported in a study in a Finnish nonagenarian cohort after 4 years of follow-up.18 In the initial NonaSantfeliu study, the mortality rate was 19.3% after 12 months of follow-up,6 rising to 36.2% after 24 months. This percentage is much higher than the rate in the general population (0.91%), similar to that for nonagenarians aged 90–94 (20.6%), and below that found in the >94 years age group (35%) reported in Catalonia in 2004.19
Age is probably the most important factor for functional decline,20 with an increase in the relative risk of a functional loss of about 2.0% for each 10 year increase.21 In this sample of very old people, nearly half of the cohort (41%) had functional decline and BI loss >19% compared with baseline basic ADL after 24 months of follow-up. It is a remarkable finding that high proportion (18.5%) of nonagenarians acquired new severe dependency.
Searching for predictive risk factors of the combined negative item of death or functional decline in these older-old subjects, we found that the best predictors of bad prognosis were low LI values and poor cognitive status at baseline. Instrumental ADL performance requires higher cognitive functioning than basic ADL. Spector et al.22 suggested that disability in instrumental ADL was a more sensitive predictor of functional decline than disability in basic ADL alone. We had confirmed these results previously in subjects aged over 89 who did not show a severe dependence status at baseline. A history of stroke and previous incapacity to undertake instrumental ADL were the best predictors of functional decline in nonagenarians after a 1-year follow-up period.2 As we were measuring the combined item of functional loss and mortality, we used LI to predict functional decline moreover another function measure—the BI—that was used to define functional loss in the present study.
Though the reports in the literature are not entirely consistent, it does seem that cognitive impairment is associated with increased mortality.23 Evaluating data from the Danish 1905 cohort survey, Andersen et al.24 found that cognitive impairment also predicts mortality among nonagenarians, even controlling for most known predictors of mortality. In our study initial cognitive status (MEC) was a significant predictor in the multivariate analysis.
The association of cognitive impairment with functional status decline is strong.20 Dementia is an important determinant of functional status.25 In this sample, the percentage of prior diagnosis of dementia was low, which may explain the lack of association with functional decline. Gill et al.26 demonstrated that among the various components of the Mini Mental Status Examination, orientation and memory items had the strongest predictive value. We evaluated all components of the MEC together.
As well as poor results in basic ADL at baseline and a high percentage of dementia, the bivariate analysis detected higher co-morbidity (Charlson Index), low MNA-SF score, higher percentage of hearing and visual impairment and low hypertension in the cohort with death or functional loss. The majority of these associations seem logical. The most surprising, perhaps, is the association of hypertension with lower mortality or loss of functional status. With respect to hypertension and mortality some studies have reported that in the oldestold subjects, higher systolic blood pressure is associated with better survival, interpreting that low blood pressure may be a marker of approaching frailty or imminent death.27,28 None of these variables remained significant in the multivariate analysis.
The main limitation of this study is the sample size, especially for males. Another limitation was that data related to other functional decline risk factors, such as hospital admissions occurring during the follow-up, were not evaluated. Furthermore, causes of death were not recorded.
Our study highlights the importance of poor instrumental ADL performance and poor cognition at baseline in the prediction of functional changes or mortality in the oldest of elderly subjects. In conclusion, the percentage of death or functional decline among the subjects is high. Better cognitive status and higher capacity to perform instrumental ADL at baseline are the best predictors to identified s which nonagenarians survived without major functional decline after a 2-year follow-up period.
Conflicts of interest: None declared.
Key points
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