Change in Smoking Status and Subsequent BMI Change Linked to NAFLD Risk

Change in body mass index (BMI) following change in smoking status is strongly associated with risk of developing nonalcoholic fatty liver disease (NAFLD), according to a study published in Gut and Liver.

While smoking is considered a risk factor for NAFLD, the study authors explained that the link between weight change after a change in smoking status and NAFLD risk is still unclear.

To assess the relationship, the authors gathered data from 2 health examination periods in the Korean National Health Insurance Service–National Sample Cohort, conducted between 2009 and 2010 and between 2011 and 2012. Their analysis included a total of 139,180 adults 40 years or older who were divided into nonsmoking, smoking cessation, smoking relapse, and sustained smoking groups.

Women made up the majority (71.8%) of this sample. The median (IQR) age was 57 (52-67) years, and the median BMI and waist circumference were 23.5 kg/m² and 80 cm, respectively.

NAFLD was defined as a fatty liver index of at least 60, and adjusted odds ratio (aOR) and 95% CI were calculated using multivariable-adjusted logistic regression.

Across all 4 smoking status groups, NAFLD risk increased among individuals who experienced an increase in BMI, and was lower among individuals who saw a decrease in BMI.

Compared with individuals who were nonsmoking and saw no change in BMI, NAFLD risk was significantly increased among those who saw an increase in BMI and:

• nonsmoking (aOR, 4.07; 95% CI, 3.77-4.39)
• smoking cessation (aOR, 5.52; 95% CI, 4.12-7.40)
• smoking relapse (aOR, 7.51; 95% CI, 4.81-11.72)
• sustained smoking (aOR, 6.65; 95% CI, 5.33-8.29)

On the other hand, also compared with nonsmokers who saw no change in BMI, NAFLD risk still slightly increased but was significantly lower among those who saw a decrease in BMI and:

• nonsmoking (aOR, 0.19; 95% CI, 0.16-0.22)
• smoking cessation (aOR, 0.40; 95% CI, 0.17-0.91)
• smoking relapse (aOR, 0.06; 95% CI, 0.01-0.45)
• sustained smoking (aOR, 0.34; 95% CI, 0.21-0.56)

Among individuals with no BMI change, smoking cessation (aOR, 1.76; 95% CI, 1.35-2.29) and sustained smoking (aOR, 1.64; 95% CI, 1.39-1.94) were both associated with higher risk of NAFLD.

The authors also found that liver enzyme levels were higher among participants who experienced both BMI gain and smoking cessation.

While the initial goal was to understand the relationship between weight and smoking status and NAFLD risk, the authors noted that having medical professionals measure BMI rather than having participants self-report their weight may lead to more accurate results.

Additionally, the patients self-reported their smoking status without listing reasons for any smoking cessation. The authors said this may slightly skew results and that reasons for cessation should be further studied.

“It is possible that the quitters may have experienced a certain disease due to smoking, which may have affected the results to a certain degree, and it was the major reason for the inclusion of CCI [Charlson comorbidity index] as an adjustment variable in multivariable analyses,” they said.

Based on these findings, the authors suggested that clinicians recommend weight management for patients following a change in smoking status to reduce the risk and disease burden of NAFLD.

“Based on our data, we conclude that weight gain after change in smoking status is a serious health concern for NAFLD in middle-aged Korean adults,” the authors concluded. “Future studies of the multiethnic cohorts are required to testify the generalizability of our findings.”

Reference

Jeong S, Oh YH, Choi S, et al. Association of change in smoking status and subsequent weight change with risk of nonalcoholic fatty liver disease. Gut Liver. Published online November 3, 2022. doi:10.5009/gnl220038