Data source
This cross-sectional study utilizes frequency tables from NHIS data on hay fever for both adults and children in 2013, 2014, 2015, 2016, 2017, and 2018 (NHIS Adult Table 2013a; NHIS Child Table 2013b; NHIS Adult Table 2014a; NHIS Child Table 2014b; NHIS Adult Table 2015a; NHIS Child Table 2015b; NHIS Adult Table 2016a; NHIS Child Table 2016b; NHIS Adult Table 2017a; NHIS Child Table 2017b; NIHS Adult Table 2018a; NHIS Child Table 2018b). NHIS is one of the major data collection programs of The National Center for Health Statistics (NCHS) a division of Center for Disease Control and Prevention (CDC). It consists of a cross-sectional household interview survey that monitors the health of the civilian noninstitutionalized population of the US and gives comprehensive information pertinent to various health topics (NHIS 2019). Survey data for children are collected from a parent or a responsible adult family member residing in the household while adult data are self-reported. From 2013 to 2018, the questions asked pertaining to child hay fever were as follows: "During the past 12 months, has {child's name} had any of the following conditions? Hay fever? Any kind of respiratory allergy? Any kind of food or digestive allergy? Eczema or any kind of skin allergy?" (NHIS Child Table 2013a; NHIS Child Table 2014a; NHIS Child Table 2015a; NHIS Child Table 2016a; NHIS Child Table 2017a; NHIS Child Table 2018a). NHIS data are released by the CDC and report the annual total frequency of cases for hay fever along with its demographic factors including race, age, sex, region, and economic factors such as health insurance, family income, and poverty status.
Adults who responded to the survey stating that they were given a diagnosis on any of the respiratory conditions like hay fever, sinusitis, and bronchitis were included in the NHIS table of selected respiratory diseases for the year of their survey (NHIS Adult Table 2013b; NHIS Adult Table 2014b; NHIS Adult Table 2015b; NHIS Adult Table 2016b; NHIS Adult Table 2017b; NHIS Adult Table 2018b). Children whose parents responded to the survey stating that they had hay fever were included in NHIS frequency table category for child hay fever for the year of their response (NHIS Child Table 2013a; NHIS Child Table 2014a; NHIS Child Table 2015a; NHIS Child Table 2016a; NHIS Child Table 2017a; NHIS Child Table 2018a).
The sociodemographic variables used in this study included race; age; sex; health insurance coverage (private, Medicaid, Other, Uninsured, Medicare and Medicaid, Medicare Advantage, and Medicare only); poverty status (poor, near poor, and not poor); region of the United States (northeast, mid-west, south, and west); and employment status (full-time, part-time, not employed but has worked previously, and not employed and has never worked); education level for ages above 25 years (less than high school diploma, high school diploma or GED, some college, and bachelor’s degree or higher). Among the parent-reported hay fever cases for children, the education level of parents was one of the covariates.
The IRB recognizes that the analysis of de-identified, publicly available data does not constitute human subjects research as defined at 45 CFR 46.102 and that it does not require IRB review. The IRB no longer requires the registration or review of studies involving the analysis of public use data sets unless a project merges multiple data sets and in so doing enables the identification of individuals whose data are analyzed.
Statistical analysis
Using frequency values for each year, the total frequency (in thousands) of hay fever each year was recorded. Within each subcategory, age-adjusted percentages of the general population were recorded from the NHIS tables for each year.
Chi-square tests
Chi-square tests were used to examine group differences among the respondents with hay fever within each year by different sociodemographic variables like sex, age group, race, employment status, health insurance, poverty status, region, and education. All statistical analyses were performed using SAS software version 9.4 (SAS Institute, Cary, NC, USA) at an a priori significance level of 0.05. Analysis was performed separately for adults and children.
Additionally, this study evaluated the trend of hay fever. Several graphs were depicted with the year plotted against the total number of hay fever cases and all the sociodemographic variables.