Abstract
Ageing is associated with reduced appetite and energy intakes. However, the mechanisms underlying this phenomenon are not fully understood. This systematic review and meta-analysis quantified differences in circulating concentrations of appetite-related hormones between healthy older and younger adults. Six databases were searched through 12th June 2018 for studies that compared appetite-related hormone concentrations between older and younger adults. Data were pooled using random-effects meta-analysis and are presented as standardised mean difference (Hedges’ g) with 95% confidence intervals (95% CI). Thirty-five studies were included involving 710 older adults (mean ± SD; age: 73 ± 5 years) and 713 younger adults (age: 28 ± 7 years). Compared with younger adults, older adults exhibited higher fasted and postprandial concentrations of the anorectic hormones cholecystokinin (Fasted: SMD 0.41 (95% CI 0.24, 0.57); p < 0.001. Postprandial: SMD 0.41 (0.20, 0.62); p < 0.001), leptin [Fasted: SMD 1.23 (0.15, 2.30); p = 0.025. Postprandial: SMD 0.62 (0.23, 1.01); p = 0.002] and insulin [Fasted: SMD 0.24 (− 0.02, 0.50); p = 0.073. Postprandial: SMD 0.16 (0.01, 0.32); p = 0.043]. Higher postprandial concentrations of peptide-YY were also observed in older adults compared with younger adults [SMD 0.31 (− 0.03, 0.65); p = 0.075]. Compared with younger adults, older adults had lower energy intakes [SMD − 0.98 (− 1.74, − 0.22); p = 0.011], and lower hunger perceptions in the fasted [SMD − 1.00 (− 1.54, − 0.46); p < 0.001] and postprandial states [SMD − 0.31, (− 0.64, 0.02); p = 0.064]. Higher circulating concentrations of insulin, leptin, cholecystokinin and peptide-YY accord with reduced appetite and energy intakes in healthy older adults. Interventions to reduce circulating levels of these hormones may be beneficial for combatting the anorexia of ageing.
Highlights
962 million people worldwide are over the age of 60 years [1] and it is predicted that 22% of the global population will be 60 years and older by 2050 [2]
Standardised mean difference and moderator variables for insulin concentrations Fasted insulin concentrations were higher in older adults than younger adults with a small difference between groups (SMD: 0.24, 95% confidence intervals (95% confidence intervals (CI)): − 0.02 to 0.50; n = 19; p = 0.073; Fig. 3a) The degree of heterogeneity may be substantial between studies (I2=74.3%, Q = 70.1, τ2 = 0.225, df = 18)
There was a trivial but significant difference in postprandial insulin concentrations between younger and older adults (SMD: 0.16, 95% CI: 0.01 to 0.32, n = 17; p = 0.043; Fig. 3b).The degree of heterogeneity was found to be low between studies (I2= 10.5%, Q = 17.9, τ2 = 0.001, df = 17)
Summary
962 million people worldwide are over the age of 60 years [1] and it is predicted that 22% of the global population will be 60 years and older by 2050 [2]. Current observations suggest that this phenomenon has a prevalence of 15–30% in independently living older adults, with higher incidence occurring in hospital and nursing home settings [3]. Current research suggests that changes in appetite-related hormones may mediate the reductions in appetite and energy intake observed in older adults. The purpose of this research was to provide a systematic review and meta-analysis of studies which compared circulating appetite-related hormone concentrations between metabolically healthy older and younger adults in the fasted and/or postprandial state, with no known co-morbidities or pre-existing medical conditions. Comparisons of appetite perceptions and energy intake between the groups were included where available. Understanding these effects contributes to the identification of potential mechanistic targets for future interventions to reduce the anorexia of ageing
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