Referee Report Risk of Non-Hodgkin Lymphoma Due to Diet

Initially, when choosing an academic article to read and analyze, I wanted to choose something that I would be really invested in. Throughout my life, my grandfather has battled non-Hodgkin lymphoma (NHL) and I wanted to research what are some possible onsets of this disease. Could it possibly be diet? Could it be hereditary? These are questions I intended to answer through my research. At the conclusion of my research, I narrowed my focus to one article, in particular, that used regressions from data collected to show the correlation between diet, among other things, and non-Hodgkin lymphoma. “Risk of Non-Hodgkin Lymphoma and Nitrate and Nitrite From Drinking Water and Diet” by Mary H. Ward, James R. Cerhan, Joanne S. Colt, and Patricia Hartge explores diet and other impurities we consume as humans in Iowa, Detroit, Seattle, and Los Angeles from 1998 to 2000.

While this study was initially done to observe nitrite and nitrate levels in water and diet in Iowa, Detroit, Seattle, and Los Angeles, Iowa was the only state observed whose nitrate levels were abnormal relative to the other states. Therefore, the study decided to isolate this state in their research and focus solely on Iowa’s diet and water composition. Nitrate is significant in this area because it is more rural, and most traces of nitrate come from fertilizer, waste, and air pollution. “This analysis was part of a population-based case-control study of non-Hodgkin lymphoma conducted in 4 4 Surveillance, Epidemiology, and End Results (SEER) centers to investigate the role of environmental exposures in NHL risk.” (375) Water sources with over 70% nitrate levels since 1960 were studied. 117 item food questionnaires were used to determine how the population’s diet played a role in their health. “Odds ratios and 95% confidence intervals were calculated using logistic regression, adjusting for the study matching factors, education, and caloric intake.” (375) By the conclusion of the study, it was determined that there was no correlation between drinking water and NHL. There was also no correlation between vitamin c, red meat, and NHL. However, it was concluded that bread and cereal did hold significant value in determining NHL susceptibility.

There were many parts of this report that I was able to appreciate. There were a lot of numbers and scientific fact included in the research. This shows me that research was done prior to this and that the review of the research was very thorough. This shows me that this report was not only made for health economists, but scientists and researchers as well. I appreciated the way they used a complete list of residences and the times they lived at these specific residences. They also used very specific dates, different from just a calendar year, to group the population into certain age groups. Data was collected from 28 years prior to when the study was conducted to have a large sample size of data. Every single type of water was examined, from private wells, public water, bottled water, and any other type of water that does not directly fit into one of these categories. (376) Concerning diet, an extensive food questionnaire was put into place that even took dietary and vitamin supplement intake into consideration. The focus of the dietary portion of the research was water intake, meat preparation methods, doneness of food/meat, and vegetable intake. Some vegetables have higher nitrate levels than others. (377) It is actually possible to have an increased risk of NHL from too much or too little vitamin C intake. (378) :The use of monitoring data for assessing exposure to nitrate has several limitations. Distribution samples taken at one or more taps quarterly or annually (as is required) may not adequately reflect exposure if there is substantial seasonal or spatial variation.” (381) I was pleased to see that the study was able to address the struggles they faced during research and the shortcomings they may have experienced. Throughout the study, I noticed parts that were not cohesive with the rest of the study or that may have hindered the overall message that it was trying to send so I appreciate the self-reflection on the part of the researchers. “Our results for NHL in Iowa do not confirm results from our previous study in Nebraska in which NHL risk increased with increasing nitrate levels in public supplies… additional studies of populations with higher exposure levels would be informative.” (382) There was also a study conducted in Nebraska that concluded the exact opposite results so for the researchers to acknowledge that is a step in the right direction for possibly one day correcting their deficiencies and getting an exact result on if these factors correlate to non-Hodgkin lymphoma. There were a few parts of the article that I did not like as well.

There were many science terms that I was not familiar with. I wish I had more of a science background to be able to understand most of the reactions the article was saying would happen with nitrate and nitrite within the body to be able to form NHL. It required me to pay attention to trends within the numbers instead of actually understanding why things are happening the way they are. I do not like that they only focused on Iowa instead of the other 3 states. I feel like you are cutting out a good chunk of your sample size by negating the data from 3 states just because they were not rural enough. During testing, more women were tested than men were and more whites were tested than other racial groups. Having different genetic make-ups, I feel that only focusing on one gender or racial group would skew the results. The study focused mostly on private wells within Iowa since public water supplies were expected to be controlled as far as water impurities and composition. I feel that this is an egregious error in assuming and could very well effect the outcome of the results. Increasing nitrite caused an increase in the risk of NHL. Most of this nitrite came from nitrite rich breads and cereals. (380) “A small percentage of the study population had more than a few years of exposure to nitrate levels.” (380) I do not see how a study can say that it is legitimate if most of the population had even been exposed to nitrate long enough for it to affect their body and possibly give them NHL. “Our study could not evaluate risk at nitrate levels above the maximum contaminant level due to the lack of historical exposure data for private wells and the infrequent exposure above this level among public water supply users.” (381) This particular research group had done 3 previous tests of the same kind in different geographic locations and the results were all different. (380) That makes me question the validity of the research.

As previously stated, I did not understand many of the scientific terms that were used in the research. I also did not understand the 4 pathologic groups that were used in the study: follicular, diffuse, t-cell, and other classifications. It seemed that they wanted to be very specific in certain aspects of the study, such as food questionnaires, but then take shortcuts in other aspects, such as cutting out ¾ of your sample size by not testing the other states. They focused on NHL cases without HIV in ages 20-74. I am not sure what having HIV has to do with NHL. I would assume these are two very separate diseases and do not correlate at all. This also cutting out your sample size. It was determined that most private wells had no nitrate, some had a bit of nitrate, and only 8 wells had concerning levels of nitrate. (377) This goes against the notion that the other 3 testing areas would not have offered any insight into nitrate levels because the rural area they tested ended up having less nitrate than the city. They used unconditional logic regression. I have gone over regressions in Econ Stats and Econometrics but have not encountered this regression yet. Therefore, I was confused as to how this regression is actually used. They also used body mass as a category of the population. I am not sure why this was used because I feel that if you have a higher body mass you will eat or drink more food that potentially contains pollutants, so it will eventually even out and body mass will not have to be taken into account. It is not as if everyone is eating or drinking the same amount. They eat or drink according to their body mass so it does not need to be accounted for. Smoking was introduced halfway into the study and I am not sure why this was not addressed earlier into the study because smoking has shown direct correlations to cancer so this was vital information that needed to be presented to the reader at the beginning of the article. (377)

Overall, the effort of the study was there. Intentions were good, but execution could have been better. There was a lot of over focusing on one aspect while not enough focus was placed in other areas. Allocation of resources, labor, and time management could have made this study a lot more effective and worthwhile because ultimately, the conclusion did not yield anything significant since their previous 3 studies all showed different results.

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