Harrison FE, Bowman GL, Polidori MC. Ascorbic acid and the brain: rationale for the use against cognitive decline. Nutrients. 2014; 6:1752–81.49 49. Bowman GL. Ascorbic acid, cognitive function, and Alzheimer’s disease: a current review and future direction. Biofactors. 2012; 38:114–22.
50 50. Bowman GL, Dodge H, Frei B, et al. Ascorbic acid and rates of cognitive decline in Alzheimer’s disease. J Alzheimers Dis. 2009; 16:93–8.
51 51. Bang HO, Dyerberg J. Plasma lipids and lipoproteins in Greenlandic west coast Eskimos. Acta Med Scand. 1972; 192:85–94.
52 52. Dyerberg J, Bang HO, Hjorne N. Fatty acid composition of the plasma lipids in Greenland Eskimos. Am J Clin Nutr. 1975; 28:958–66.
53 53. Shahidi F, Ambigaipalan P. Omega‐3 polyunsaturated fatty acids and their health benefits. Annu Rev Food Sci Technol. 2018; 9:345–81.
54 54. Chen CT, Domenichiello AF, Trépanier MO, Liu Z, Masoodi M, Bazinet RP. The low levels of eicosapentaenoic acid in rat brain phospholipids are maintained via multiple redundant mechanisms. J Lipid Res. 2013; 54:2410–22.
55 55. Chen CT, Liu Z, Bazinet RP. Rapid de‐esterification and loss of eicosapentaenoic acid from rat brain phospholipids: an intracerebroventricular study. J Neurochem. 2011; 116:363–73.
56 56. Zhang W, Li P, Hu X, Zhang F, Chen J, Gao Y. Omega‐3 polyunsaturated fatty acids in the brain: metabolism and neuroprotection. Front Biosci (Landmark Ed). 2011; 16:2653–70.
57 57. Bazan NG. Docosanoids and elovanoids from omega‐3 fatty acids are pro‐homeostatic modulators of inflammatory responses, cell damage and neuroprotection. Mol Aspects Med. 2018; 64:18–33.
58 58. Bazinet RP, Laye S. Polyunsaturated fatty acids and their metabolites in brain function and disease. Nat Rev Neurosci. 2014; 15:771–85.
59 59. Dong Y, Xu M, Kalueff AV, Song C. Dietary eicosapentaenoic acid normalizes hippocampal omega‐3 and 6 polyunsaturated fatty acid profile, attenuates glial activation and regulates BDNF function in a rodent model of neuroinflammation induced by central interleukin‐1β administration. Eur J Nutr. 2018; 57:1781–91.
60 60. Witte AV, Kerti L, Hermannstadter HM, et al. Long‐chain omega‐3 fatty acids improve brain function and structure in older adults. Cereb Cortex. 2014; 24:3059–68.
61 61. Schwarz C, Wirth M, Gerischer L, et al. Effects of Omega‐3 fatty acids on resting cerebral perfusion in patients with mild cognitive impairment: a randomized controlled trial. J Prev Alzheimers Dis. 2018; 5:26–30.
62 62. Bowman GL, Dodge HH, Mattek N, et al. Plasma omega‐3 PUFA and white matter mediated executive decline in older adults. Front Aging Neurosci. 2013; 5:92.
63 63. Bowman GL, Silbert LC, Dodge HH, et al. Randomized trial of marine n‐3 polyunsaturated fatty acids for the prevention of cerebral small vessel disease and inflammation in aging (PUFA Trial): rationale, design and baseline results. Nutrients. 2019; 11.
64 64. Rodgers GP, Collins FS. Precision nutrition – the answer to ‘what to eat to stay healthy’. JAMA. 2020; 324:735–6.
65 65. Bowman G, Gouskova N, Dodge H, et al. Pre‐analytical and within‐person reproducibility of nutritional metabolomics over 2 years in elders at risk for dementia (P18‐121‐19). Current Developments in Nutrition. 2019; 3.
CHAPTER 13 The anorexia of aging
Neema Sharda1, Jantira Thomas2, and Ian M. Chapman3
1 Division of Geriatric Medicine, Duke University, Durham, North, Carolina, USA
2 Division of Geriatric Medicine, Wake Forest University, Winston‐Salem, North, Carolina, USA
3 University of Adelaide, Royal Adelaide Hospital, Adelaide, Australia
Introduction
In many older adults, the decrease in energy intake is greater than the decrease in energy expenditure, so body weight is lost. This physiological, age‐related reduction in energy intake has been termed anorexia of ageing.1 Undernutrition is common in older adults, with a significant impact on outcomes including physical function, healthcare utilization, and length of hospital stays.2–5 According to the World Health Organization, malnutrition refers to deficiencies, excesses, or imbalances in a person’s energy intake. Malnutrition encompasses both undernutrition and obesity6; in this chapter, malnutrition and undernutrition are used interchangeably. The Global Leadership Initiative on Malnutrition established that the diagnosis includes a phenotypic criteria (non‐volitional weight loss, low body mass index, or reduced muscle mass) and a etiologic criteria (reduced food intake or absorption, or underlying inflammation due to acute or chronic disease/injury).7 A key predictor of malnutrition in older adults is loss of appetite.8 The prevalence of malnutrition depends on the population, geography, and living situation. One study from 2010 reported a review of the Mini Nutritional Assessment across settings in Europe, the United States, and South Africa; the prevalence of malnutrition was 22.8% (n = 4507, mean age 82.3, 75.2% female), with the highest rates for patients in rehabilitation units (50.5%), less for hospitalized older adults (38.7%), and lower among community dwellers (5.8%).9 More recently, in 2016, a meta‐analysis on malnutrition in various European healthcare settings suggested the following malnutrition rates: 6.0% (95% CI 4.6–7.5); hospital, 22.0% (95% CI 18.9–22.5); nursing homes, 17.5% (95% CI 14.3–20.6); long‐term care, 28.7% (95% CI 21.4–36.0); rehabilitation/sub‐acute care, 29.4% (95% CI 21.7–36.9).10
As indicated in this chapter, (i) ideal weight ranges are almost certainly higher in older than younger adults; (ii) weight loss is often associated with adverse effects in the elderly, particularly if unintentional; and (iii) undernutrition manifesting as low body weight and weight loss is common in older adults and has significant adverse effects. Healthcare providers should maintain a high level of awareness to detect unintentional weight loss and undernutrition in this age group.
‘Ideal’ body weight in older people
There is increasing evidence that the adverse effects of being overweight or obese, as defined by standard body mass index (BMI) criteria, are not as great in the elderly as in younger adults.11 Ideal weight ranges based on life expectancy are higher for older than young adults. For example, in a 12‐year study of 324,000 people in the American Cancer Society Cohort, for people under the age of 75, there was a significant and progressive increase in subsequent mortality as baseline BMI increased above 21.9 kg−2. However, these adverse effects of increasing body weight diminished with increasing age above 45 years and were absent altogether over 75 years. Among 4736 people age 60 or more followed for an average of 4.5 years in the Systolic Hypertension in the Elderly Program (SHEP), those whose baseline BMI was in the lowest quintile (<23.6 kg−2) had the highest subsequent mortality and those within the highest BMI quintile (≥31 kg−2), corresponding to the conventional criteria of obesity, had the lowest mortality.12,13
Recommendations for ideal weight ranges in older people vary, but there is strong evidence that BMI values below about 22 kg−2 in people over 70 are associated with worse outcomes than higher weights, and BMIs below 18.5 kg−2 are a particular concern. The optimum BMI for survival in people over age 70 is
