Physical activity in aging: comparison among young, aged, and nonagenarian individuals

Abstract

Physical activity (PA) is known to decline with age; however, there is a paucity of data on activity in persons who are in their nineties and beyond. We used objective and reliable methods to measure PA in nonagenarians (>or=90 yr; n=98) and hypothesized that activity would be similar to that of aged (60-74 yr; n=58) subjects but less than in young (20-34 yr; n=53) volunteers. Total energy expenditure (TEE) was measured by doubly labeled water over 14 days and resting metabolic rate (RMR) by indirect calorimetry. Measures of PA included activity energy expenditure adjusted for body composition, TEE adjusted for RMR, physical activity level (PAL), and activity over 14 days by accelerometry expressed as average daily durations of light and moderate activity. RMR and TEE were lower with increasing age group (P<0.01); however, RMR was not different between aged and nonagenarian subjects after adjusting for fat-free mass, fat mass, and sex. Nonagenarians had a lower PAL and were more sedentary than the aged and young groups (P<0.01); however, the nonagenarians who were more active on a daily basis walked further during a timed test, indicating higher physical functionality. For all measures of activity, no differences were found between young and aged volunteers. PA was markedly lower in nonagenarians compared with young and aged adults. Interestingly, PA was similar between young volunteers and those who were in their 60s and 70s, likely due to the sedentary nature of our society, particularly in young adults.

Fig. 1.

Absolute total energy expenditure (TEE) and its components. *TEE and resting metabolic rate (RMR) measured by indirect calorimetry were significantly lower with age among all groups in men (P < 0.01) and lower in nonagenarian women compared with young and aged women (P < 0.001). †Activity energy expenditure (AEE), calculated as TEE − (RMR + TEF) was significantly lower in the nonagenarians compared with the young (P < 0.01) and aged groups (P < 0.05) for men and women. TEF = thermic effect of food estimated as 10% of TEE. Overall, women had lower TEE than men (P < 0.001); Table 2 shows that this sex effect was true in each category.

Fig. 2.

Top: physical activity level (PAL) in the 3 groups. PAL is a ratio [TEE/(RMR + 0.1 × TEE)], and no units are assigned to it. *PAL was significantly lower in the nonagenarian group compared with the young and aged groups (P < 0.001). Bottom: residual of TEE after adjusting for RMR. Residual values represent the difference between predicted and measured values of adjusted TEE and indicate the amount of energy expended in activity. *Residuals were lower in the nonagenarian group compared with the aged group (P = 0.02) and young group (P = 0.08). Residuals were not different between the young and aged groups (P = 0.96).

Fig. 3.

Daily physical activity as recorded by an activity monitor (Actigraph) worn over 14 days. Data are presented as minutes per average 24-h day spent in light activity [<574 counts/min (cpm) or activity intensity of 1 to ≤3 metabolic equivalents (METs)] and moderate activity (574–4,945 cpm or activity intensity of >3 to ≤6 METs). Light activity included time spent sleeping. *Nonagenarians spent significantly more time being sedentary or in low-intensity activity than either the aged or young groups (P < 0.001) and less time in moderate-intensity activity (P < 0.001). Activity was not different between the young and aged groups (P = 0.32 and P = 0.34, respectively).

Fig. 4.

Relationship between PAL and distance walked (m) during a 6-min test for nonagenarians and aged subjects. For the combined sample, distance walked was significantly related to PAL (r = 0.44, P < 0.001). When separated by age group, nonagenarians with a higher PAL were able to walk further during the timed test (r = 0.29, P = 0.01), and there was a trend for the same relationship in aged subjects (r = 0.26, P = 0.06).