Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 354

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 probably in the range 25–30 kg⁻², and there is some recent evidence that BMIs above ‘normal’ may be somewhat more protective in women than men.¹⁴

Although optimum body weight for older adults is higher than that for young adults, they tend to weigh less. The decline in body weight with age, as measured by BMI, has been well documented in population‐based, cross‐sectional, and longitudinal studies. For example, in the 1997–1998 US National Health Interview Survey of 68,556 adults, more people 75 and older than those 45–64 were ‘underweight’ (BMI <18.5; 5 vs. 1.2%) and substantially fewer were ‘overweight’ (BMI >25; 47.2 vs. 63.5%).^15,16