Analyzing 6,676 participants from the Guangdong Gut Microbiome Project, this cross-sectional study identified 222 OTUs (operational taxonomic units) linked to firsthand smoking and 117 to secondhand smoke exposure. Among never-smokers, aging alone associated with 330 OTUs. Critically, 85 OTUs overlapped between smoking- and age-associated signals, and mediation analysis implicated systolic blood pressure as a partial mediator between this shared microbial signature and atherosclerotic cardiovascular disease (ASCVD) risk scores. Notably, smoking-related microbiome deviations were more pronounced in younger adults than older ones.
The mechanistic implication here is genuinely interesting: smoking may accelerate a microbiome aging trajectory that converges on the same dysbiotic state that older adults reach through time alone. This convergence theory has been emerging in geroscience, where multiple stressors — smoking, obesity, chronic stress — appear to phenocopy accelerated biological aging. The blood pressure mediation finding adds a plausible physiological pathway connecting gut ecology to cardiovascular endpoints, likely through microbial modulation of short-chain fatty acid production and systemic inflammation.
Limitations are significant: this is cross-sectional, precluding causal inference, and the cohort is exclusively Chinese, limiting generalizability. The OTU-level analysis is also less precise than modern amplicon sequence variant approaches. Still, the scale of 6,676 participants lends statistical credibility. This is confirmatory-to-incremental work, but the age-stratified smoking effect is a genuinely novel observation worth pursuing in longitudinal designs.
