Medical Bulletin 25/ February/ 2025 - Video

As traditional candles burn, they can contribute to indoor air pollution by emitting volatile compounds and smoke, which may pose inhalation risks. Scented wax melts are often marketed as safer alternatives to candles because they’re flame- and smoke-free. But in a study in ACS’ Environmental Science & Technology Letters, researchers describe how aroma compounds released from the melted wax can react with ozone in indoor air to form potentially toxic particles.

The potential for nanoparticle formation during wax-melt use was unknown. So, Nusrat Jung, Brandon Boor and colleagues set out to investigate this process using wax melts in a full-scale house model that mimicked a typical residential house.

The researchers conducted experiments on 15 commercially available wax melts, both unscented and scented (e.g., lemon, papaya, tangerine and peppermint), in the model house. They first established a baseline of indoor air pollutants and then switched on the wax warmer for about 2 hours. During and after this period, the researchers continuously sampled the air a few yards (meters) away from the wax melts and found airborne nanoparticles, between 1 and 100 nanometers wide, at levels that were comparable to previously reported levels for traditional, combustion-based candles. These particles could pose an inhalation risk because they are small enough to pass through respiratory tissues and enter the bloodstream, say the researchers.

In the experiments, the main VOCs emitted from the wax melts were terpenes, such as monoterpenes and monoterpenoids. The researchers identified that the airborne terpenes reacted with ozone and formed sticky compounds, which aggregated into nanoscale particles. However, after warming an unscented wax melt, the team observed no terpene emissions or nanoparticle formation, which suggests that these aroma compounds contribute to nanoparticle formation.

The researchers say this study challenges the perception that scented wax melts are a safer alternative to combustion-based candles; however, they emphasize that more toxicology research is needed on the risks of breathing in nanoparticles formed from wax melts.

Ref: Satya S. Patra, Jinglin Jiang et al. Flame-Free Candles Are Not Pollution-Free: Scented Wax Melts as a Significant Source of Atmospheric Nanoparticles, Environ. Sci. Technol. Lett. 2025, 12, 2, 175–182. 10.1021/acs.estlett.4c00986

A team of researchers from Syracuse University and Michigan State University recently explored the personal characteristics that help people handle prolonged stressors, such as the pandemic. Led by Jeewon Oh, assistant professor of psychology in Syracuse University’s College of Arts and Sciences, the group delved into optimism and pessimism and how those mindsets influence well-being.

The group utilized data from the Health and Retirement Study, a large-scale panel study where the participants responded to questions assessing their levels of optimism, such as “In uncertain times, I usually expect the best,” and pessimism, such as “I hardly ever expect things to go my way.” During the COVID-19 pandemic, respondents answered questions on health-related behaviors that either increased or reduced the risk of COVID transmission, including masking frequency, travel habits and the likelihood of staying home.

Among their findings, they found that greater optimism promotes resilience and well-being when faced with stressors like the pandemic, while lower pessimism is linked to safer health behaviors. Their findings appeared in the Journal of Research in Personality.

Separating optimism and pessimism, the researchers found that only pessimism was associated with behaviors that reduce risk, but both optimism and pessimism were associated with psychological well-being. By investigating them in the context of new public health challenges, the team found that while the presence of optimism and absence of pessimism may both be resources for well-being, the absence of pessimism may be particularly important for health-relevant behaviors.

Ref: Jeewon Oh, Emily N. Tetreau, Mariah F. Purol, Eric S. Kim, William J. Chopik,

Optimism and pessimism were prospectively associated with adaptation during the COVID-19 pandemic, Journal of Research in Personality, Volume 113, 2024, 104541, ISSN 0092-6566, https://doi.org/10.1016/j.jrp.2024.104541.

The 2023 American College of Rheumatology and American Association of Hip and Knee Surgeons Clinical Practice Guideline concluded that obesity alone should not delay joint replacement. Therefore, a substantially increased utilization of joint replacement among patients with obesity could be expected. However, patients with obesity are at increased risk of revision, posing unique challenges as the surgery is complex and costly, and it remains unknown whether postoperative weight loss could decrease the risk of revision.

With this, the researchers conducted the present study to examine the association of the proportion of postoperative weight loss following antiobesity medication use with the risk of revision among patients with obesity undergoing hip or knee replacement.

The results showed that among 3691 qualified participants, the 5-year risks of revision were 5.6%, 4.4%, and 3.7% for weight gain or stable, small-to-moderate weight loss, and large weight loss groups, respectively.

Compared with the weight gain or stable group, the hazard ratios (HRs) were 0.75 for the small-to-moderate weight loss group and 0.57 for the large weight loss group. Similar results were observed when the analyses were performed separately for hip or knee replacement. Consistent findings were obtained regarding the association of weight loss with the 10-year risks after initiating antiobesity medications.

Hence, it was concluded that in this cohort study using a target trial emulation, a higher proportion of weight loss after initiating antiobesity medications within 1 year was associated with a lower risk of 5-year and 10-year revision among patients with obesity undergoing joint replacement. These results suggest that antiobesity medication use, with relatively safe and sustainable weight loss, may be an effective strategy for improving implant survivorship of hip and knee replacements in the obese population.

Ref: Xie D, Englund M, Lane NE, Zhang Y, Li X, Wei J, Zeng C, Lei G. Postoperative Weight Loss After Antiobesity Medications and Revision Risk After Joint Replacement. JAMA Netw Open. 2025 Feb 3;8(2):e2461200. doi: 10.1001/jamanetworkopen.2024.61200. PMID: 39982723; PMCID: PMC11846009.

The association of digital screen time with myopia has been documented, but the dose-response association and safe exposure threshold remain unclear.

Therefore, this study was aimed to evaluate the dose-response association of time spent on digital screens with myopia risk. Primary research articles investigating the association of exposure to digital screen devices (ie, smartphones, tablets, game consoles, computers, or television) with myopia-related outcomes (ie, prevalent or incident myopia and the rate of myopia progression) were identified by reviewers.

The results of the reviews showed that of 45 studies with 335 524 participants an additional hour of daily screen time was associated with higher odds of myopia. The nonlinear DRMA of 34 studies with 314 910 participants also indicated higher odds of myopia with increasing screen time, ranging from 1 hour of daily exposure to 4 hours. The dose-response curve showed myopia risk increasing significantly between 1 to 4 hours of daily screen time, and then rising more gradually after 4 hours.

Therefore, the authors revealed that in this systematic review and DRMA, a daily 1-hour increment in digital screen time was associated with 21% higher odds of myopia and the dose-response pattern exhibited a sigmoidal shape, indicating a potential safety threshold of less than 1 hour per day of exposure, with an increase in odds up to 4 hours. These findings can offer guidance to clinicians and researchers regarding myopia risk.

Ref: Ha A, Lee YJ, Lee M, Shim SR, Kim YK. Digital Screen Time and Myopia: A Systematic Review and Dose-Response Meta-Analysis. JAMA Netw Open. 2025;8(2):e2460026. doi:10.1001/jamanetworkopen.2024.60026