What factors may increase the risk of active TB? —Chinese large sample cohort study

Tuberculosis, caused by Mycobacterium tuberculosis, is one of the leading causes of infectious disease death worldwide
.

According to statistics, about 1/4 of people worldwide are infected with Mycobacterium tuberculosis, and about 5% to 15% of infected people develop active tuberculosis
.

This study aims to explore
this study in depth the joint correlation between multiple factors in lifestyle (including smoking, low body mass index, physical inactivity, alcohol consumption, and low dietary quality) and the risk of active tuberculosis.

This study was a prospective cohort study that included health data
from 63,257 Singaporeans aged 45 to 74 who were enrolled between 1993 and 1998.

Information on physical activity, smoking history, alcohol consumption, habitual diet, and medical history (including diabetes, hypertension, coronary heart disease, stroke, and cancer) was collected at baseline
.

After excluding common TB cases (n = 3012) at baseline, 60,245 participants (25 914 males) were included; 43.
0%) for analysis
.

At the same time, a second follow-up was conducted from 2006 to 2010 to update the information of
39,528 participants.

As of December 31, 2016, researchers identified new cases
of active TB through data from the TB Registry Study.

The Cox proportional risk regression model was used to calculate the risk ratio (HR) and 95% confidence interval (CI)
associated with TB risk by the Lifestyle Risk Factor Composite Score.

The five main risk factors in the Lifestyle Risk Factors Composite Score are defined as smoking, underweight (BMI less than 20.
0 kg/^m2), physical inactivity (moderate exercise < 2 hours/week or strenuous exercise <0.
5 hours/week), alcohol consumption, and low dietary quality (low intake of fish/shellfish and vegetables/fruits).
<b11>
The results of each risk factor assessment correspond to a score of 1 (at risk) or 0 (reference value
).

The Lifestyle Risk Factor Composite Score is the sum of 5 individual risk factors, with a score of 0 to 5, and the higher the score, the greater the
number of risk factors.

During follow-up, 1358 new cases
of active tuberculosis were finally confirmed.

The mean age at which participants were diagnosed with TB was 69.
4 years [standard deviation (SD), 9.
2 years
].

The proportion of participants with 0, 1, 2, 3, 4 and 5 risk factors was 14.
7%, 47.
3%, 27.
8%, 8.
4%, 1.
9% and 0.
2%,
respectively.

Subjects with higher overall scores were more male and older at baseline, with lower educational attainment, lower BMI, and lower tea drinking frequency
.

Reports show that each risk factor is independently associated
with a higher risk of active TB.

In the Kaplan-Meier survival curve, elevated risk factor scores correlated with reduced survival (logarithmic rank test P< 0.
0001
).

After adequate correction of potential confounders, subjects with 1, 2, 3, 4, and 5 risk factors multivariate corrected HR (95% CI) for 1.
24 (1.
02-1.
51), 1.
84 (1.
51-2.
23), 2.
52 (2.
03-3.
14), 4.
07 (3.
07-5.
41), and 9.
04 (5.
44-15.
02) (Ptrend), respectively, compared with subjects with 0 risk factors <0.
0001) (Table 1).

Table 1 Correlation between individual/combined risk factors in lifestyle and the risk of active tuberculosis

Note: The covariates in Model 1 include gender, age at recruitment, year of recruitment (1993-1995, 1996-1998), different dialect groups (Hokkien, Cantonese), education level (no formal education, primary school, secondary school or higher), tea drinking (none, monthly, weekly, daily), and total energy intake
.

Individual risk factor analysis is adjusted
in the model.

Model 2 further corrected for diabetes, hypertension, coronary heart disease, stroke, and cancer
in the subjects' medical histories.

In addition, the risk of active tuberculosis in diabetic participants at baseline increased with increasing the number of lifestyle risk factors, and the correlation was significantly stronger than that of non-diabetic subjects (Pinteraction = 0.
01).


HR (95% CI) of 4 to 5 risk factors in participants with diabetes was [9.
14 (4.
27 to 19.
57)] much higher than that of 0 risk factors [4.
34 (3.
25 to 5.
79)].

This prospective cohort study of older middle-aged and older adults suggests that smoking, underweight, physical inactivity, alcohol consumption, and low dietary quality are associated
with a significant increased risk of active tuberculosis.

There were 5 risk factor subjects with a 9-fold increased risk of active TB compared to 0 risk factor subjects, suggesting that risk factors in multiple lifestyles are associated
in a synergistic manner with active TB risk.

Previous studies have shown that smoking and underweight are risk factors for TB, and this study also showed that smokers had a roughly 2-fold higher risk of TB than non-smokers, while subjects with a BMI of less than 20.
0 kg/^m2 had a higher risk of
TB.

Although the relationship between specific dietary factors and TB susceptibility has not been fully established, insufficient intake of fruits and vegetables and fish/shellfish is positively associated
with TB risk.

Studies have also shown that smoking may interact with alcohol consumption and low dietary quality, increasing the risk of
active tuberculosis.

Therefore, improving the quality of diet and reducing alcohol intake may have greater benefits for smokers, and public education programs to quit smoking should also emphasize the importance of
improving diet quality and reducing alcohol intake.

In addition, the coexistence of 4 or more risk factors significantly increases the risk of active TB in patients with diabetes, suggesting that these risk factors may have a synergistic effect with diabetes, further increasing the risk
of disease in this group.

Therefore, lifestyle changes should be included in the management of
diabetic patients.

Huiqi Li, Cynthia B E Chee, Tingting Geng, An Pan, Woon Puay Koh, Joint Associations of Multiple Lifestyle Factors With Risk of Active Tuberculosis in the Population: The Singapore Chinese Health Study, Clinical Infectious Diseases, Volume 75, Issue 2, 15 July 2022, Pages 213–220.