Of the 18,024 participants in the Vukuzazi cohort (68% female, median age 37 years [interquartile rage 23–56 years]), 1,301 (7.2%) reported current smoking, 150 (0.8%) reported former smoking and 16,573 (92%) reported never smoking. Of those who currently smoked, 1069 (82%) reported smoking cigarettes, 175 (13%) smoking cigars, 23 (1.8%) smoking pipes, 441 (33.9%) smoking bidis, and 37 (2.8%) smoking hukkah either daily or weekly. Table 1 shows the demographic characteristics of the participants by smoking status. Among people who reported current smoking, the median age was 37 years (interquartile rage 27–49 years) and the majority were male (n = 1,177; 90.5%). Compared to people reporting former or never smoking, people reporting current smoking were more likely to be male, younger, and more overweight or obese. People who reported former smoking were older, more likely to be unemployed, and more likely to be in the poorest household socio-economic status quintile compared to those who reported current or never smoking.
P-values shown are from Chi-Square tests for smoking category (including former smoking) with demographic characteristics. All values are frequencies are reported with percentages in parenthesis. *BMI: Less than 18.5 = Underweight, 18.5 to 24.9 = Healthy, 25 to 29.9 = Overweight and 30 or higher = Obese.
The percentage of participants with HIV was similarly high among the three smoking categories (current 34.6%, former 33.6%, never 33.9%; p-value = 0.879) (Table 2). However, among PLWH, detectable viremia was more common in people reporting current smoking compared to people reporting former or never smoking (28.8% vs. 12.0% vs. 16.6%; p-value < 0.001). The percentage of participants with active TB was significantly higher among people reporting current or former smoking (current, 3.1%; former, 4.7%) compared to people who reported never having smoked (1.3%, p-value < 0.001). In contrast, hypertension and diabetes mellitus were less common in people reporting current smoking (17.1% and 2.5%, respectively) than people reporting former smoking (31.5% and 14.8%) or never smoking (26.2% and 10.2%, p-values for both hypertension and diabetes mellitus were < 0.001). Stratification of these data by sex revealed that among males, the percentage of participants who had each of the conditions defined (HIV, HIV with detectable viremia, active TB, hypertension and diabetes mellitus) all differed significantly by smoking status (Table 3). This includes a significantly higher prevalence of HIV in males reporting current smoking compared with males reporting former or never smoking. In contrast, in females, there were no significant differences in CDs or NCDs by smoking status (Supplementary Table 1).
Multivariable regression models comparing percentage of participants with CDs and NCDs among people with current smoking and never smoking status, stratified by sex and adjusted for potential confounders (age and socio-economic status), are shown in Table 4. We did not include former smoking in the multivariable regression models since only 150 participants (0.8%) were in this category. In the multivariable model, we found no relationship between being HIV-positive and current smoking in either males or females (adjusted odds ratio [aOR] = 1.10, 95% confidence interval [CI]: 0.93–1.30, p = 0.272; and aOR = 1.25, 95% CI: 0.83–1.89, p = 0.278, respectively), nor did we find any relationship between viremic HIV and current smoking in either males or females (aOR = 0.85, 95% CI 0.63–1.15, p = 0.291; and aOR = 0.87, 95% CI 0.43–1.77, p = 0.698, respectively). In males, we found an increased odds of active TB among people reporting current smoking compared with never smoking (aOR = 1.95, 95% CI: 1.22–3.13, p = 0.006). Also in males, current smoking was associated with lower odds of hypertension (aOR = 0.67, ,95% CI: 0.54–0.83, p-value < 0.001) and diabetes mellitus (aOR = 0.38, 95% CI: 0.24–0.61, p-value < 0.001) compared with never smoking. In females, there was no increase in odds of active TB, hypertension or diabetes mellitus in people reporting current smoking compared with people reporting never smoking. To better understand the relationship between body weight, tobacco use and chronic disease, we included BMI in the multivariable regression (Supplementary Table 2). The direction of all relationships held true in this analysis.
Table 4
Association between communicable and non-communicable diseases and smoking status, multivariable regression.
VARIABLE
|
MALES
|
FEMALES
|
|
Adjusted odds ratio (95% CI)
|
P-value
|
Adjusted odds ratio (95% CI)
|
P-value
|
HIV (positive ELISA result)
|
|
|
|
|
Never smoking
|
Reference
|
|
Reference
|
|
Current smoking
|
1.10 (0.93; 1.30)
|
0.272
|
1.25 (0.83; 1.89)
|
0.278
|
Viral load < 400 copies/mL among those with HIV
|
|
|
|
|
Never smoking
|
Reference
|
|
Reference
|
|
Current smoking
|
0.85 (0.63; 1.15)
|
0.291
|
0.87 (0.43; 1.77)
|
0.698
|
Active tuberculosis
|
|
|
|
|
Never smoking
|
Reference
|
|
Reference
|
|
Current smoking
|
1.95 (1.22; 3.13)
|
0.006
|
1.95 (0.58; 6.53)
|
0.280
|
Hypertension
|
|
|
|
|
Never smoking
|
Reference
|
|
Reference
|
|
Current smoking
|
0.67 (0.54; 0.83)
|
< 0.001
|
0.80 (0.49; 1.30)
|
0.366
|
Diabetes mellitus
|
|
|
|
|
Never smoking
|
Reference
|
|
Reference
|
|
Current smoking
|
0.38 (0.24; 0.61)
|
< 0.001
|
0.63 (0.30; 1.34)
|
0.227
|
For each outcome variable (HIV, viral load < 400 copies/mL, tuberculosis, hypertension, and diabetes mellitus), we ran separate multivariable logistic regression models, adjusting for age and household socio-economic status. All logistic regression models excluded former smoking due to small numbers in the category. CI: Confidence Interval |