*3.2. Hardy-Weinberg Equilibrium and Genotype Frequencies and Genetic Susceptibility*

The three SNPs that were evaluated comply with the HWE: rs13118928 (*p* = 0.23), rs1828591 (*p* = 0.16), and rs13147758 (*p* = 0.40).

The DNA samples of 743 women with and without COPD who were exposed to biomass-burning smoke were genotyped, and three SNPs (rs13147759, rs1828591, and rs13118928) were evaluated. The relationship between cases and controls is 1 case for 2.99 controls; therefore, the statistical power of our study is 90% using the following parameters: an OR = 2, a ratio of controls to case 3:1, a MAF = 15%, and a confidence interval of 95%.

Table 2 shows the results of the genotype frequencies; in the three polymorphisms, the AA genotype was determined to be the most common genotype, and the GG genotype was the least frequently observed genotype. Interestingly, the heterozygous genotypes in both groups occurred in more than 40% of our study population.

The GG homozygous genotype of rs13118928 shows a decreased risk of developing the disease (*p* = 0.038), and the statistical test used was the χ<sup>2</sup> test. The analyses with the rs13147758 and rs1828591 polymorphisms did not demonstrate significant differences.

Furthermore, all significant results were adjusted for possible confounding variables (age, BMI, and BSEI) through a logistic regression model, where the rs13118928 GG genotype maintained its association with decreased risk (adjusted *p* = 0.021, OR = 0.51, 95% CI 0.27–0.97).


**Table 2.** Genotype frequencies among study groups.

COPD-BS: COPD related to biomass-burning exposure; BBES: exposed to biomass-burning smoke. *p* < 0.05 statistical significance; \* *p*-value adjusted by age, BMI, and BBEI. Associations are shown in the full genotype model.

### *3.3. Genetic Models*

The three polymorphisms were analyzed by the codominant and recessive genetic association models; as observed in Table 3, rs13118928, which showed a decreased risk of disease susceptibility in the genotype frequencies, maintained this result with the GG genotype in the recessive model (*p* = 0.038, adjusted *p* = 0.0023 OR = 0.51, 95% CI = 0.27–0.97). The OR and the confidence interval were maintained in both analyses, and the *p*-value was strengthened after the logistic regression analysis, demonstrating that minor allele homozygous carriers have a decreased COPD risk.

**Table 3.** Analysis by genetic models of rs13118928 in exposed to biomass-burning smoke with and without COPD.


COPD-BS: COPD related to biomass-burning exposure; BBES: biomass-burning smoke-exposed subjects. *p* < 0.05 statistical significance; \* *p*-value adjusted by age, BMI, and BBEI.

#### *3.4. Haplotypes*

Supplementary Figure S1 presents the haplotypes identified in the rs13147758 and rs1828591 polymorphisms. Four haplotypes were formed, with two showing significant trends: AA (*p* = 0.07, OR = 1.25, 95% CI = 0.98–1.60) and AG (*p* = 0.06, OR = 0.53, 95% CI = 0.27–1.02). Figure 1 shows the haplotypes formed by rs1828591 and rs13118928 (r2 = 0.54); the haplotype formed by both minor

alleles (G) presented a decreased risk of disease (*p* = 0.04, OR = 0.65, CI95% = 0.43–0.98). In the analysis examining the three SNPs, no haplotypes were determined to be associated.


**Figure 1.** Haplotypes of rs1828591 and rs13118928 in the *HHIP* gene. COPD-BS: COPD related to biomass-burning exposure; BBES: Biomass-burning smoke-exposed subjects: *p* < 0.05 demonstrates significance; OR: odds ratio; CI 95%: 95% confidence interval; showing r2 values among SNPs.
