Introduction: Smoking affects the occurrence and
development of many diseases. We attempt to study the structure of
intestinal flora in the middle-aged and elderly population as well
as how smoking affects the intestinal flora. Methods: We collected population information, biochemical indicators, and
patient feces from 188 middle-aged and elderly male patients, and
their feces were tested for the 16S rRNA gene of intestinal flora. Results: We performed a cluster analysis on the intestinal
structure of the included population and found that there was a significant
difference in the number of smokers between each group (p = 0.011). Subsequently, the microbiological diversity analysis of
current smokers and nonsmokers was carried out. The results indicated
that there was a significant difference in species composition between
the two groups (p = 0.029). Through the analysis
on LEfSe differential bacteria, it was found that in current smoking
patients, the abundances of the genus Bifidobacterium and the genus
Coprobacillus were less, while the abundances of the genera Shigella,
Paraprevotella, Burkholderia, Sutterella, Megamonas, and p-75-a5 under
the family level of Erysipelotrichaceae were slightly high. We analyzed
the correlation between the abundances of these eight different bacteria
and clinical indicators. The results revealed the following: the abundance
of the genus Bifidobacterium was negatively correlated with fasting
blood glucose (r = −0.198, p = 0.006) and positively correlated with uric acid (r = 0.207, p = 0.004) and total bilirubin (r = 0.175, p = 0.017); Shigella bacteria
were positively correlated with fasting blood glucose (r = 0.160, p = 0.028) and uric acid (r = 0.153, p = 0.036) levels; the genus Paraprevotella
and BMI (r = −0.172, p =
0.018) are negatively correlated; the abundance of the genus Burkholderia
was positively correlated with γ-glutamyltransferase (r = 0.146, p = 0.045) levels; Sutterella
was correlated with fasting blood glucose (r = 0.143, p = 0.05) and creatinine level (r = −0.16, p = 0.027), which was positively correlated with fasting
blood glucose and negatively correlated with creatinine. Conclusions: In middle-aged and elderly patients with cardiovascular disease,
smoking can reduce the abundance of Bifidobacterium, while the abundances
of some negative bacteria such as Burkholderia, Sutterella, and Megamonas
increase.