Table 1 Studies investigating aging and the gut microbiome humans

Hopkins et al. (2002) [130]

15

British

21–34 years

67-88 years

67–73 years CDAD

Bacteroides species diversity

Bifidobacteria species diversity

↑

↓

CDAD patients had greater diversity lactobacilli/clostridia but reducted bacteriodes, prevotella, and bifidobacteria

Hayashi et al. (2003) [131]

6

Japanese

79–84 years^a

Clostridium rRNA subcluster XIVa

Bifidobacteria #

Ruminoccoccus obeum

↓

Woodmansey et al. (2004) [132]

28

British

19–35 years

67–75 years

73–101 years HE

Bacterioides

Bifidobacteria (no. and diversity)

↓

Hospitalized patients displayed age-related changes along with increased proteolytic bacteria no. and diversity

Van Tongeren et al. (2005) [74]

23

Dutch

70–100 years

N/A

N/A

High frailty scores associated with reduced lactobacilli, bacteroides, prevotella no.; increased enterobacteria

Biagi et al. (2010) [70]

84

Italian

25–40 years

59–78 years

99–104 years

Clostridium cluster XIVa

Bacilli

Proteobacteria

↓

↑

↑

Young and elderly showed similar microbiota, while differences observed in centenarians only.

Claesson et al. (2011) [72]

170

Irish

28–46 years

>65 years

Firmicutes

Clostridium cluster IV

Ruminococcaceae

↓

↑

↑

Claesson et al. (2012) [73]

191

Irish

28–46 years

64–102 years

N/A

N/A

Microbiota composition clustered by diet and residence location + significantly correlated with frailty, co-morbidity, and inflammation

Rampelli et al. (2013) [71]

9

Italian

38–102 years

Bacterial DNA gene expression for:

short-chain fatty acid production

Proteolytic functions

Pathobionts

↓

↑

↑

Jeffery et al. (2016) [40]

371

Irish

64–102 years

N/A

N/A

Longitudinal samples revealed temporal instability of microbiota

Low microbial diversity associated with greater temporal instability

Long-term care stays and antibiotic use associated with increased alterations in microbial composition and diversity

Jackson et al. (2016) [41]

1008

British

Irish

42–102 years

N/A

N/A

Robust associations between frailty and gut microbiota

F. prausnitzii negatively associated

E. dolichum and E. lenta positively associated

Odamaki et al. (2016) [133]

367

Japanese

0–104 years

Proteobacteria/Bacteroidetes

Firmicutes/Actinobacteria

↓

↑

Cattaneo et al. (2017) [42]

83

Italian

Mean ~ 70 years^b

N/A

N/A

Gut microbial populations and peripheral inflammatory cytokines associated with cognitive impairment and brain amyloidosis