Meet a CTS Researcher

Charlie Zhong was recently awarded his PhD in Epidemiology from the University of Southern California (USC). He shared with us how his work on the California Teachers Study has shaped his future research goals.

Tell us about how you first got involved with the California Teachers Study.

I started working on the CTS on a project focused on stroke. When you do studies on health like we do in the CTS, you need to find out who has a certain disease, and you need to think about which data source is most reliable for the health outcome you’re interested in.

One way to identify who has had a stroke is to look at hospitalization data; generally, when you have a stroke, you’re hospitalized. The Office of Statewide Health Planning and Development (OSPHD) database collects data on anyone who is hospitalized in California for an in-patient stay.

The goal of this project was to identify how accurately OSPHD data captured who in the CTS had had a stroke. In other words, can we use OSPHD data for our studies on stroke and be confident that those data are accurate for our population?

To answer this question, we recruited 200 CTS participants who had had a stroke according to OSPHD data who gave us permission to review their medical records. The medical records confirmed that they had indeed had a stroke.

By doing this comparison we determined that OSPHD is a reliable source of stroke data. This means that instead of asking every single CTS participant whether they have had a stroke, we can use OSPHD data to study risk factors for stroke and use data all the way back to when the cohort started.

Did the California Teachers Study play any role in your PhD research?

Yes! My dissertation was about environmental sources of inflammation and non-Hodgkin lymphoma (NHL) risk. Lymphoma is a blood cancer/ cancer of your lymph nodes. Established risk factors for lymphoma are family history, certain diseases that cause inflammation—like lupus—and infections that cause your immune system to go into overdrive.

Because there is an established relationship between inflammation and lymphoma, I was curious about whether sleep disruption—particularly sleep disruption due to light at night— was also associated with NHL risk. A lot of research has shown sleep disruption to be carcinogenic for breast cancer. My hypothesis was that light pollution disrupts your sleep, which causes inflammation, which may increase the risk of NHL.

The study that I conducted for my dissertation from 2016 – 2019 found that there is an association between light at night and risk of NHL, particularly for diffuse large B-cell lymphoma (DLBCL).

So, what’s next for you?

I want to build upon the light at night research in the future. I haven’t examined noise pollution yet; light and noise are likely the two major sleep disruptors, so it would be interesting to see if there is any association between noise pollution and NHL risk.