Sex-Related Cochlear Impairment in Cigarette Smokers

Transgenerational effects of maternal exposure to nicotine on structures of pituitary-gonadal axis of rats

Smoking can lead to several diseases and cause a reduction in fertility in men and women. Among the various components of cigarettes harmful during pregnancy, nicotine stands out. It can cause a reduction in placental blood flow, compromising the development of the baby with neurological, reproductive and endocrine consequences. Thus, we aimed to evaluate the effects of nicotine on the pituitary-gonadal axis of rats exposed during pregnancy and breastfeeding (1st generation - F1), and whether the possible damage observed would reach the 2nd generation (F2). Pregnant Wistar rats received 2 mg/kg/day of nicotine throughout the entire gestation and lactation. Part of the offspring was evaluated on the first neonatal day (F1) for macroscopic, histopathological and immunohistochemical analyses of brain and gonads. Another part of the offspring was kept until 90 days-old for mating and obtainment of progenies that had the same parameters evaluated at the end of pregnancy (F2). The occurrence of malformations was more frequent and diversified in nicotine-exposed F2. Brain alterations, including reduced size and changes in cell proliferation and death, were seen in both generations of nicotine-exposed rats. Male and female gonads of F1 exposed rats were also affected. The F2 rats showed reduced cellular proliferation and increased cell death on the pituitary and ovaries, besides increased anogenital distance in females. The number of mast cells was not enough altered to indicate an inflammatory process in brain and gonads. We conclude that prenatal exposure to nicotine causes transgenerational alterations in the structures of pituitary-gonadal axis in rats.

Maternal factors associated with smoking during gestation and consequences in newborns: Results of an 18-year study

BACKGROUND

Tobacco use is one of the most important causes of obstetric and perinatal pathologies. Its frequency during pregnancy is high and could be related to various socioeconomic and cultural characteristics of the mothers.

AIM

The aim of this study is to determine the trend and prevalence of smoking in pregnant mothers in our area over the years and the socio-cultural or obstetric factors associated with smoking as well as the repercussions on the newborns related to its consumption.

METHODS

Retrospective study of 18,959 mothers of healthy newborns in the maternity ward of the regional hospital during the years 2002-2019. The variable under study was maternal smoking during pregnancy compared with various maternal, obstetric, and perinatal factors.

RESULTS

A mean percentage of 20.4% of the mothers smoked, with significantly decreasing percentages over the years. There was a significant association between smoking and mothers' age, origin, level of education, the occurrence of previous abortions, parity, type of breastfeeding at discharge, type of delivery, low birth weight, and need for neonatal resuscitation.

CONCLUSIONS

This defines a profile of pregnant smokers on whom it is important to act: young, Spanish, with a low level of education, multiparous, and with previous miscarriages. Its repercussions are also evident with a lower birth weight in newborns. Knowledge of these factors will make it possible to design more effective intervention strategies to reduce smoking during pregnancy.

RELEVANCE FOR PATIENTS

Any effort that reduces smoking habits can improve the health status of mothers and newborns and the first step is to know who are risk pregnants.

Self-reported and cotinine-verified smoking and increased risk of incident hearing loss

We examined the associations of smoking status and urinary cotinine levels, an objective measure of smoking, with the development of new-onset HL. This cohort study was performed in 293,991 Korean adults free of HL who underwent a comprehensive screening examination and were followed for up to 8.8 years. HL was defined as a pure-tone average of thresholds at 0.5, 1.0, and 2.0 kHz ≥ 25 dB in both ears. During a median follow-up of 4.9 years, 2286 participants developed new-onset bilateral HL. Self-reported smoking status was associated with an increased risk of new-onset bilateral HL. Multivariable-adjusted HRs (95% CIs) for incident HL comparing former smokers and current smokers to never-smokers were 1.14 (1.004-1.30) and 1.40 (1.21-1.61), respectively. Number of cigarettes, pack-years, and urinary cotinine levels were consistently associated with incident HL. These associations were similarly observed when introducing changes in smoking status, urinary cotinine, and other confounders during follow-up as time-varying covariates. In this large cohort of young and middle-aged men and women, smoking status based on both self-report and urinary cotinine level were independently associated with an increased incidence of bilateral HL. Our findings indicate smoking is an independent risk factor for HL.

Cigarette Smoking, Smoking Cessation, and Risk of Hearing Loss in Women

BACKGROUND

Previous studies demonstrated higher risk of hearing loss among cigarette smokers, but longitudinal data on whether the risk is influenced by smoking cessation are limited. We prospectively investigated relations between smoking, smoking cessation, and risk of self-reported moderate or worse hearing loss among 81,505 women in the Nurses' Health Study II (1991-2013).

METHODS

Information on smoking and hearing status was obtained from validated biennial questionnaires. Cox proportional hazards regression was used to estimate multivariable-adjusted relative risks (MVRR, 95% confidence interval).

RESULTS

During 1,533,214 person-years of follow-up, 2760 cases of hearing loss were reported. Smoking was associated with higher risk of hearing loss and the risk tended to be higher with greater number of pack-years smoked. Compared with never smokers, the MVRR (95% confidence interval) among past smokers with 20+ pack-years of smoking was 1.30 (1.09-1.55) and 1.21 (1.02-1.43) for current smokers. The magnitude of elevated risk diminished with greater time since smoking cessation. Compared with never smokers, the MVRR among smokers who quit <5 years prior was 1.43 (1.17-1.75); 5-9 years prior was 1.27 (1.03-1.56); 10-14 years prior was 1.17 (0.96-1.41); and plateaued thereafter. Additional adjustment for pack-years smoking attenuated the results.

CONCLUSIONS

The higher risk of hearing loss associated with smoking may diminish over time after quitting.

Behavioral Hearing Thresholds and Distortion Product Otoacoustic Emissions in Cannabis Smokers

Purpose Cannabis is a widely used drug both medically and recreationally. The aim of this study was to determine if cannabis smoking is associated with changes in auditory function, as measured by behavioral hearing thresholds and/or distortion product otoacoustic emissions (DPOAEs). Method We investigated hearing thresholds and 2f₁-f₂ DPOAEs in 20 cannabis smokers and 20 nonsmokers between 18 and 28 years old. Behavioral thresholds were obtained from 0.25 to 16 kHz. DPOAEs were measured using discrete tones between f₂ of 0.5 and 19.03 kHz using an f₂/f₁ ratio of 1.22 and L₁/L₂ = 65/55 dB SPL. Thresholds and DPOAE amplitudes were compared between groups using linear mixed-effects models with sex and frequency as predictors. Results Behavioral thresholds in smokers did not differ significantly between smokers and nonsmokers (all ps > .05). Although not significant, long-term smokers exhibited poorer thresholds than short-term smokers and nonsmokers. Smokers generally exhibited lower DPOAE amplitudes than nonsmokers, although the differences were not significant. Male smokers had significantly poorer DPOAE amplitudes than male nonsmokers in the low frequencies (f₂ ≤ 2 kHz; p = .0245). Conclusion Results indicate that smoking cannabis may negatively alter the function of outer hair cells in young men. This subtle cochleopathology is evident in the absence of measurable differences in behavioral hearing thresholds between cannabis smokers and nonsmokers.

Chronic cigarette smoke exposure drives spiral ganglion neuron loss in mice

Tobacco use is associated with an increased risk of hearing loss in older individuals, suggesting cigarette smoke (CS) exposure may target the peripheral auditory organs. However, the effects of CS exposure on general cochlear anatomy have not previously been explored. Here we compare control and chronic CS exposed cochleae from adult mice to assess changes in structure and cell survival. Two-photon imaging techniques, including the imaging of second harmonic generation (SHG) and two-photon excitation fluorescence (TPEF) from native molecules, were used to probe the whole cochlear organ for changes. We found evidence for fibrillar collagen accumulation in the spiral ganglion and organ of Corti, consistent with fibrosis. Quantitative TPEF indicated that basal CS-exposed spiral ganglion neurons experienced greater oxidative stress than control neurons, which was confirmed by histological staining for lipid peroxidation products. Cell counts confirmed that the CS-exposed spiral ganglion also contained fewer basal neurons. Taken together, these data support the premise that CS exposure induces oxidative stress in cochlear cells. They also indicate that two-photon techniques may screen cochlear tissues for oxidative stress.