2.2 Otros
2.2.2 Sistema inmune artificial
The relative contribution of increased fat mass to mortality may be less pronounced in elderly people. There is some variability between studies. In 2032 subjects (999 men, 1033 women; mean age, 80 years) recruited by random sampling of the Old Age and Disability Allowance Schemes in Hong Kong, stratified by sex and 5-year age groups from 70 years onward, overall mortality was negatively associated with body mass index and participation in physical activity, after adjusting for age and sex.33 In another study, older men and women at a BMI range of 25 to less than 32 kg/m2 were shown to have no excess mortality.34 The BMI range of 25 to 27 has also been reported not to be risk factor for all-cause and cardiovascular mortality among elderly persons, whereas overweight (BMI ≥ 27) was a significant prognostic factor for all-cause and cardiovascular mortality among 65- to 74-year-olds, and there was also a significant positive association between overweight and all-cause mortality among those 75 years or older. Overall, it is clear that higher BMI values are associated with a smaller relative mortality risk in elderly persons than in young and middle-aged populations. The standardized mortality rate increases with increasing BMI, but within each BMI group, the standardized mortality rate decreases with age.35
A high waist circumference (in nonsmoking men) may be a better predictor of all-cause mortality than high BMI.19 In a prospective cohort study of 31,702 healthy Iowa women age 55 to 69 years, the waist:hip ratio was the best anthropometric predictor of total mortality.36 In men and women age 67 to 78, the waist circum-ference and supine sagittal abdominal diameter are most closely related to CVD risk factors.37
In 1996, a health survey was mailed to all surviving participants 65 years or older from the Chicago Heart Association Detection Project in Industry Study (1967 to 1973). The response rate was 60%, and the sample included 3981 male and 3099 female respondents. Compared with normal-weight people, both underweight and obese older adults reported impaired quality of life, particularly worse physical functioning and physical well-being. These results reinforce the importance of nor-mal body weight in older age.38
The elderly at greatest risk are those who are simultaneously sarcopenic and obese.17 Low BMI and weight loss in the elderly are both strong and independent predictors of subsequent mortality, and low BMI better predicts mortality than low waist circumference.19 Prior weight history has also been shown to be important in
50 Geriatric Nutrition predicting risk. Older heavier people who gained more than 10% of mid-life body weight or thinner older people who had lost 10% or more of body weight show high risk compared with thinner people with stable weight.39 Using data from a large, population-based California cohort study, the Leisure World Cohort Study, it has been shown that in the elderly obesity has been associated with increased mortality only among persons under age 75 years and among never or past smokers. In addition, being overweight or obese in young adulthood and underweight or obese in later life increases the risk of premature mortality in the elderly.40
4.6.2 GENERAL HEALTHAND WELL-BEING
In the elderly, as in younger individuals, although there have been health improve-ments in a number of areas, chronic and obesity-related diseases are increasing. For example, in Manitoba, Canada, the prevalence of diabetes, hypertension, and demen-tia increased substandemen-tially over a 14-year period in approximately 50,000 individuals over the age of 65.41
4.6.3 DISEASE-SPECIFIC RISKS
4.6.3.1 Mobility-Related Disability
Among 2714 women and 2095 men, 65 to 100 years, there was a positive association between fat mass and disability at baseline. Moreover, fat mass was predictive of disability 3 years later, independent of low fat-free mass, age, physical activity, or chronic disease.42 Data from the U.S. National Health and Nutrition Examination Survey (NHANES) I (1971 through 1987) showed that high BMI is a strong predictor of long-term risk for mobility disability in older women and that this risk persists even to very old age. In the English Longitudinal Study of Ageing, a national population sample of 1030 women and 888 men age 55 to 74 years, body mass and shape were major determinants of disability. Increased waist circumference was the best predictor for most disability outcomes.21 Sarcopenic obesity at baseline is particularly predictive of independent activities of daily living (IADL) disability at follow-up after 8 years.43 Large population-based studies have shown that obesity is a significant indepen-dent predictor for older persons being homebound44 or losing independence, partic-ularly when associated with an unhealthy diet and physical inactivity.45 A paradoxical increase in risk in disability has been associated with weight loss in very elderly women.46 Moreover, the Women’s Health Initiative Observational Study undertaken in 40 U.S. clinical centers and involving 40,657 women age 65 to 79 at baseline and 3 years of follow-up showed that both obesity and underweight were strongly associated with the development of frailty.47
4.6.3.2 Impaired Glucose Tolerance and Type 2 Diabetes Mellitus
The prevalence of type 2 diabetes increases progressively with age, peaking at 16.5%
in men and 12.8% in women age 75 to 84 years. Over age 65, diabetes or glucose intolerance was present in 30 to 40% of Framingham Study subjects.48 Among 1972
Obesity in Older Adults 51 male participants in the Department of Veterans Affairs Normative Aging Study cohort, there was a prospective relation between abdominal adiposity and the risk of diabetes.49 An age-associated increase in total adiposity is a major contributor to impaired glucose tolerance in middle-aged and older men. Increased body fatness and increased abdom-inal obesity, rather than aging per se, are thought to be directly linked to the greatly increased incidence of type 2 diabetes mellitus among the elderly.50 Nevertheless, there is evidence that insulin secretion decreases with age even after adjustments for differ-ences in adiposity, fat distribution, and physical activity.51
4.6.3.3 Hypertension and Cardiovascular Disease
Data from the Honolulu Heart Program show that obesity and high blood pressure continue to be highly correlated even in old age.52 Furthermore, the Veterans Admin-istration Normative Aging Study showed that abdominal accumulation of body fat, apart from overall level of adiposity, was associated with both increased blood pressure and an increased risk of hypertension.53
Fat and distribution in the middle appear to be the dominant predictor of cardio-vascular risk in the elderly. Body mass index has been shown to be an important risk factor for fatal coronary heart disease (CHD), and its prognostic significance remains after up to 30 years of follow-up.54 Moreover, for individuals with no cardiovascular risk factors, as well as for those with one or more risk factors, those who are obese in middle age have a higher risk of hospitalization and mortality from CHD, cardio-vascular disease, and diabetes in older age than those who are normal weight.55 4.6.3.4 Fatty Liver
The prevalence of fatty liver has been reported to be 3.3% in male and 3.8% in female nonobese and 21.6% in male and 18.8% in female obese elderly individuals, and was shown to be an independent correlate of coronary risk factors.56
4.6.3.5 Pulmonary Function
Among 1094 men and 540 women from the Baltimore Longitudinal Study of Aging there was a strong inverse association of waist/hip ratio (WHR) with FEV(1) and FVC in men but not women.57 In a cross-sectional evaluation, the effects of fat distribution and body composition on lung function were determined in 2744 men age 60 to 79 years from towns in Britain. All men were free of cardiovascular disease and cancer. Total body fat and central adiposity were found to be inversely associated with lung function. Increased fat free mass (FFM) reflecting increased muscle mass was associated with better lung function and lower odds of low FEV1:FVC with aging.58 Weight loss has been shown to improve static lung volume, not dynamic pulmonary function, in moderately obese, sedentary men.59
4.6.3.6 Autonomic Nervous System Dysfunction
Abdominal-to-peripheral fat distribution explains a significant portion of the variance in a number of autonomic-circulatory functions attributable to aging.60
52 Geriatric Nutrition
4.6.3.7 Cognitive Function
Obesity is defined by BMI and waist circumference is associated with poorer cog-nition in the elderly.61 Moreover, obesity at midlife is associated with an increased risk of dementia and Alzheimer’s disease (AD) later in life, and clustering of vascular risk factors increases the risk in an additive manner.62 A larger WHR may be related to neurodegenerative, vascular, or metabolic processes that affect brain structures underlying cognitive decline and dementia.63
4.6.3.8 Other Adverse Effects of Obesity in the Elderly
Obesity is independently associated with the presence and severity of urinary incontinence64 and lower limb joint pain.65 Obesity also increases the risk of overall cancer, non-Hodgkin’s lymphoma, leukemia, multiple myeloma, and cancers of the kidney, colon, rectum, breast (in postmenopausal women), pancreas, ovary, and prostate.66
4.7 MANAGEMENT OF OBESITY IN THE ELDERLY