Summary Philip James, MD, Bertil Steen, MD, David Lipschitz, MD, lvar Werner, MD, and Robert E. Olson, MD

Life expectancy of nearly all populations of the world has been extended during this century because of changes in the princi- pal causes of death. At the turn of the cen- tury, infections in children and young adults were a common cause of death, but now the principal mortality factors are re- lated to disease of the cardiovascular sys- tem and to cancers. In some Western soci- eties, furthermore, there has been a progressive decline in cardiovascular dis- ease and certain kinds of cancer. These changes have brought an increase in the proportion of people over 65 years of age.

Body composition of the aged is altered from that in youth. Body compositon re- flects the interaction of genetic factors, physical activity, nutrition, and disease. Many studies document an increase in the amount of body fat with increased age. There is also a redistribution of body fat from extremities to trunk in women and from subcutaneous sites to deep adipose tissues in both men and women with in- creasing age.

Obesity in the elderly, as in other age groups, is associated with a number of life- threatening diseases. Increased mortality rates are observed in very obese individ- uals. What is unclear is the cutting point for this vulnerable group. What is the body mass index at which mortality is increased in the old-age group, which might be quite different from that observed in middle-aged individuals?

Body cell mass, especially muscle mass, decreases with age, apparently at a higher rate in males than in females. Type II fibers,

which are responsible for rapid move- ments, are particularly vulnerable to loss in the aged. Physical training, including strength but not endurance training, is ef- fective in improving the function of mus- cles, but no increase in muscle mass or consistent change in fiber type has been demonstrated. The type of training is im- portant, particularly since older people have more difficulty with eccentric move- ments that have to do with rapid adjust- ments in isometric contractions needed for descent on a stairs or a hill. These move- ments are less well conserved in elderly persons than are concentric movements, which have to do with isotonic contrac- tions.

Total body water, involving both extra- cel I u lar and in trace1 I u lar water, decreases with age. The dehydration is especially risky in the elderly because they experi- ence less thirst than younger persons, al- though they have been shown to have higher plasma sodium and osmolality in conditions of water deficit.

Bone mass also declines with age, result- ing in osteopenia. The prevalence of osteo- porosis as the cause of osteopenia is in- creasing more in urban than in rural areas. The etiology of osteoporosis is not fully un- derstood, but is clearly multifactorial. In many countries there has been a marked increase in some fractures in the aged, suggesting bone loss due to osteoporosis. Important contributing factors include physical inactivity, smoking, alcohol intake, leanness, estrogen deficiency and, possi- bly, long-standing low calcium and fluoride

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intakes. Several studies show that exercise intervention can be effective in increasing bone mineral content in those at risk for osteoporosis. Some authorities believe that the recommended intake of calcium may be too low for postmenopausal women, but proof of need is not available. When cal- cium is prescribed, it should be in an ab- sorbable form.

An age-related decline in immune func- tion is well documented. Thymic involution is thought to be the central mechanism ac- counting for the decrease in T-cell function and diminution in cell-mediated immunity that occurs with aging. Modest declines in humoral immunity have also been reported. These changes result in diminished host defenses against infection, which contrib- ute to the high prevalence of a variety of infections in older persons. Reduced im- mune surveillance may also explain, in part, the higher prevalence of malignancy in older persons.

Studies in a number of animal models have shown that restriction of energy (calo- rie) intake can significantly prolong life in both short- and long-lived animal strains. In selected animals, dietary restriction can markedly delay the appearance of age- related diseases such as atherosclerosis, glomerulonephritis, and various cancers. Dietary restriction, in fact, delays immuno- logic senesence so that T-cell function re- mains intact, lymphokine levels do not de- crease, and a unique population of 6-cells with T-cell markers remains detectable for extended periods of time. Thus, energy re- striction in animals appears to be the most important dietary element in prolonging life, with dietary fat playing a significant but less important role. Dietary calorie and fat restriction, furthermore, can delay and re- duce the rate of appearance of carcinoma of the breast and colon in susceptible ani- mal models.

There is some epidemiologic evidence linking the risk of carcinoma of the breast and colon to dietary energy and fat intakes. Although long-term caloric restriction can delay immunologic senesence in animals, the evidence that this occurs in human

beings is not available. Paradoxically, it is true, however, that human nutritional defi- ciencies in later life can significantly aggra- vate age-related abnormalities in immu- nologic and hematologic function. For example, protein-energy malnutrition and zinc deficiency cause a decline in cell-me- diated immunity in aging men and women. There is some evidence that a defect in neutrophil function may also contribute to increased mortality from bacterial infec- tions. Correcting nutritional deficiencies in older people can result in a significant im- provement in host defense, as has been demonstrated in children.

The role of nutrition in preserving mental function into old age is uncertain, but the problems of confusion, mental depression, and dementia in the elderly are very sub- stantial. Mental disease itself can lead to nutritional deficiencies because confused, depressed, and demented people forget to eat or become anorectic. Occasionally, the elderly may actually have increased nu- trient requirements, which are usually re- duced with old age, i f hypermetabolism as- sociated with infection supervenes, and this may, in turn, contribute to their con- fused state. Widespread malnutrition is evi- dent in geriatric hospitals despite the avail- ability of food. Feeding sick, infirm, and mentally confused oldsters can be time- consuming and demanding and requires special training of the hospital staff.

Specific nutritional deficiencies of thia- min, niacin, pyridoxine, and vitamin B,,, and excessive alcohol cause well-recog- nized disorders of the central nervous sys- tem, but the subtle effects of energy depri- vation associated with semistarvation are often overlooked. The availability of amino acids or choline to the brain for neuro- transmitter synthesis is of hypothetical im- portance, but whether one can alter the pattern of mental function in the old person by altering diet is less certain.

In most societies the pattern of mental disease is affected by the frequency of strokes and by cerebral atherosclerosis. These complications of stroke are more frequent in Japan, but Alzheimer’s disease

110 NUTRITION REVIEWSIVOL 46, NO PIFEBRUARY 1988

is a major problem in many countries. The patterns of mental disease in different com- munities require additional study. Further- more, the effectiveness of different nutri- tional therapies in subgroups of sick, elderly patients remains to be established.

Atherosclerosis accounts for more than half of the deaths among elderly people in the affluent world. In addition, cerebral and cardiovascular disease is the main cause of physical and psychic disability and reduced quality of life in persons over 50 years of age.

The risk factors for atherosclerosis in- clude hypercholesterolemia, cigarette smoking, hypertension, obesity, physical inactivity, and diabetes. Although these risk factors will predict CHD in individuals over 65 years of age, the precise contribution of these factors to risk in the older age group will not be quantitatively the same as in younger individuals. Obesity is clearly identified as an independent risk factor for CHD at ail ages. The reduction of body weight, preferably by both increasing phys- ical activity and reducing energy intake, has a beneficial effect on diabetes and hy- pertension. A reduction in total fat intake, particularly those fats containing saturated fatty acids, may also be beneficial. Addi- tionally, there is increasing current interest in the possible differential effects of 17-6 and n-3 polyunsaturated fatty acids derived from vegetables and fish in preventing ath- erosclerosis and even reducing atheroma- tosis. A reduction in sodium consumption may also reduce blood pressure in the por- tion of the hypertensive population that is responsive to sodium intake.

The role of nutrition in preserving the health of the elderly begins with healthful diets in youth and middle age. The nutri-

tion-sensitive risk factors for the major chronic degenerative diseases including osteoporosis, diabetes, atherosclerosis, and cancer should be controlled prior to the at- tainment of age 65. There is a great individ- ual variation in the response to nutritional measures in all age groups. These mea- sures include calorie control for preserva- tion of appropriate weight, regulation of calcium intake for preservation of bone mass, alteration of the intake of saturated fats and polyunsaturated fats of both n-6 and n-3 varieties for the adjustment of serum cholesterol and lipoprotein patterns, and reduction of salt intake for the possible control of blood pressure.

Conferees raised the question of whether the whole elderly population should be ad- vised to adjust their dietary patterns to pre- vent progression of chronic diseases or only those who are particularly at risk and responsive to dietary changes. Certainly the medical profession has a responsibility to ensure that individuals at risk are identi- fied and given advice regarding smoking, physical activity, and diet.

It was recommended that particular care should be taken to encourage older people who are sick and underweight to take more appetizing food of high nutrient quality. This advice should not be prejudiced by the idea that all the elderly should be on a pru- dent diet. Dietary plans for the elderly under medical treatment, therefore, should be adjusted to the needs of the patient, many of whom are undernourished and need encouragement to eat more rather than less. General advice to the elderly to practice variety and moderation in their food choices is an essential part of sound medical and public health practice.

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