Background
Healthy ageing frameworks have been highly explored. Our objective was to assess existing frameworks for healthy ageing and to identify commonly described factors that can potentially act as determinants of healthy ageing.
Methods
We carried out a systematic review by searching five electronic databases (EMBASE, MEDLINE, Cochrane, PsychINFO, and CINAHL) from January 2010 to November 2020 to capture contemporary evidence. Eligible studies needed to report a clear framework of healthy ageing in humans, within one or more of three domains (physical, mental/cognitive, social), in English. No restriction was placed on geographical location. Retrospective studies, studies that did not report a framework of healthy ageing, and studies with a focus on diagnostic measures were excluded.
Results
Of 3329 identified records, nine studies met our eligibility criteria and were included. Most of the studies were qualitative or cross sectional, and a majority were carried out in Asia, followed by North America, Australia, and Africa. The ten determinants identified for healthy ageing include physical activity, diet, self-awareness, outlook/attitude, life-long learning, faith, social support, financial security, community engagement, and independence.
Conclusions
We identified ten determinants of healthy ageing proposed by the contemporary evidence base. There appears to be increasing acknowledgement of the instrumental role of social and mental/cognitive well-being as determinants of healthy ageing. The extent to which each determinant contributes to healthy ageing requires further evaluation.
Supplementary Information
The online version contains supplementary material available at 10.1007/s40520-021-02049-w.
Coupling 13 C natural abundance and 14 C pulse labelling enabled us to investigate the dependence of 13 C fractionation on assimilate partitioning between shoots, roots, exudates, and CO 2 respired by maize roots. The amount of recently assimilated C in these four pools was controlled by three levels of nutrient supply: full nutrient supply (NS), 10 times diluted nutrient supply (DNS), and deionised water (DW). After pulse labelling of maize shoots in a 14 CO 2 atmosphere, 14 C was traced to determine the amounts of recently assimilated C in the four pools and the d 13 C values of the four pools were measured. Increasing amounts of recently assimilated C in the roots (from 8% to 10% of recovered 14 C in NS and DNS treatments) led to a 0.3‰ 13 C enrichment from NS to DNS treatments. A further increase of C allocation in the roots (from 10% to 13% of recovered 14 C in DNS and DW treatments) resulted in an additional enrichment of the roots from DNS to DW treatments by 0.3‰. These findings support the hypothesis that 13 C enrichment in a pool increases with an increasing amount of C transferred into that pool. d 13 C of CO 2 evolved by root respiration was similar to that of the roots in DNS and DW treatments. However, if the amount of recently assimilated C in root respiration was reduced (NS treatment), the respired CO 2 became 0.7‰ 13 C depleted compared to roots. Increasing amounts of recently assimilated C in the CO 2 from NS via DNS to DW treatments resulted in a 1.6‰ d 13 C increase of root respired CO 2 from NS to DW treatments. Thus, for both pools, i.e. roots and root respiration, increasing amounts of recently assimilated C in the pool led to a d 13 C increase. In DW and DNS plants there was no 13 C fractionation between roots and exudates. However, high nutrient supply decreased the amount of recently assimilated C in exudates compared to the other two treatments and led to a 5.3‰ 13 C enrichment in exudates compared to roots. We conclude that 13 C discrimination between plant pools and within processes such as exudation and root respiration is not constant but strongly depends on the amount of C in the respective pool and on partitioning of recently assimilated C between plant pools.
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