How Do Active and Passive Cigarette Smokers in Iran Evaluate Their Health? A Sex-Specific Analysis on the Full-Spectrum of Quality of Life.

Introduction: This study aimed to determine the sex-specific effects of active and passive cigarette smoking on the full spectrum of health-related quality of life (HRQoL) among a sizeable adult population.

Methods: This study was conducted within the Tehran Lipid and Glucose Study (TLGS) framework. Participants included 7478 adults in the last examination of the TLGS. We used a quantile regression model to compare sex-specific HRQoL distributions among non-, current, and passive smokers. Two-step cluster analysis was used to consider the synergic effects of confounder variables.

Results: In men, current smoking was negatively associated with only mental HRQoL in all percentiles of its distribution with a decrease in absolute estimation values from the lowest (5th: β = -6.59, p < .001) to the highest (90th: β=-0.93, p = .027). Also, passive smoking was negatively associated with men's physical HRQoL in the upper percentiles of its distribution (75th: β = -1.12, p = .010; 90th: β = -1.26, p = .016). In women, the current (β = -4.17 to -4.45 for 25th to 90th percentiles) and passive smokers (β = -2.05 to -4.25 for 10th to 90th percentiles) had lower mental HRQoL in the mentioned percentiles. Also, the current smoking had a negative association with the 5th percentile (β = -2.04, p = .008), and a positive association with the 50th (β = 1.94, p < .008) and 75th percentile of physical HRQoL (β = 2.25, p = .004).

Conclusions: The present study showed the harmful effect of smoking on mental HRQol in all participants. In contrast, the physical effect of smoking was only observed in female active smokers and at the extreme levels of the physical HRQoL spectrum.

Implications: According to the harmful effect of smoking on HRQoL, understanding active and passive smokers' perceptions of how smoking impacts their health is critical for tobacco control programs. Since most previous studies of smoking and HRQoL have mainly focused on the extreme parts or central values of the HRQoL distribution, the use of a multiple regression approach enables the evaluation of other parts of the conditional distribution of the outcome variable. This study demonstrated the prominent effect of smoking on the mental HRQoL as well as the more serious public health burden of passive smoking in women.