NCHStats

https://www.cdc.gov/nchs/pressroom/podcasts/2022/20220527/20220527.htm

(Based on the June 16, 2021, webinar, National Health and Nutrition Examination Survey 2017–March 2020 Pre-pandemic Data Release )

HOST:  On this edition of Statcast, we continue with the second part of the NHANES webinar, which focuses on the plans for the prepandemic and partial year 2020 data, with an overview of a published report from 2021 on health estimates from this data set, from Dr. Bryan Stierman

STIERMAN:  The health outcomes selected for estimates include for children, obesity and dental caries; for adults, hypertension, obesity, severe obesity, and diabetes; and for older adults, complete tooth loss. These health outcomes were selected for estimates because they were able to be calculated from the files currently released publicly available on the NHANES website.

Today we present estimates by several covariates including sex, age groups, race and Hispanic origin, and family income. Other covariates and stratification by sex are included in the accompanying National Health Statistics Report publication.

As is usual with NHANES analyses, to calculate these estimates we accounted for the complex, multistage probability design of NHANES, including the unequal probability of selection.

Provided sample weights were used for calculations. For estimates for diabetes, fasting sample weights were used. For all other estimates, examination simple weights for used. Standard errors were estimated using Taylor series linearization. And adult estimates were directly age-adjusted to the 2000 projected U.S. census population.

As would be expected, the overall estimates for each health outcome calculated for 2017 through March 2020 are similar to those from 2017 through 2018 alone. This reflects both the methodological adjustments, as well as the patterns in the prevalence estimates, which typically are not expected to vary by large amounts from when one year to the next in NHANES due to the relatively small sample size and a one-year data collection.

The data from 2017 through March 2020 provide an increase in sample size, generally about 1.5 to 2 times the sample size of that from 2017 through 2018 alone. As expected, this increase in sample size generally leads to smaller standard errors, as can be seen with all health outcomes here except for complete tooth loss. However, for some estimates in some demographic subgroups, increased variation in the sampling weights, increased variation in the true underlying population values of the health outcomes from the data added from 2019 through March 2020, or both may result in equivalent or increased variance of estimates, as seen here with complete tooth loss, which has equivalent standard errors from both time periods.

We found that 19.7% of children aged 2 through 19 years had obesity, defined as a body mass index greater than or equal to the 95th percentile for age and sex. There was no difference in obesity by sex. Obesity increased with increasing age groups. The highest prevalence of obesity was among non-Hispanic Black and Hispanic children. While non-Hispanic Asian children had a lower prevalence of obesity than other race and Hispanic origin groups, obesity decreased with increasing family income.

Dental caries in childhood was defined here as untreated or restored dental caries in one or more primary or permanent teeth. 46% of children aged 2 through 19 had dental caries. There is no difference in dental caries by sex. Dental caries increased with increasing age groups. Hispanic children had the highest prevalence of dental caries among children. And dental caries decreased with increasing family income. For hypertension, the estimates are based on a different methodology than those previously published for NHANES. Prior NHANES hypertension estimates have used an auscultatory protocol for blood-pressure measurements. During 2017 through 2018, both an auscultatory protocol, which utilizes a manually obtained blood pressure with a mercury sphygmomanometer, and an oscillometric protocol, which utilizes an automated machine to obtain blood pressure, were used. However, during 2019 through March 2020, only an oscillometric protocol was used. Therefore, blood-pressure measurements and hypertension estimates for the combined 2017-through-March 2020 pre-pandemic data required the use of the oscillometric protocol. The differences in these protocols and a comparison of the blood-pressure values from each protocol are available in a separate Series 2 report from NCHS.

We define hypertension here as meeting any of the following three conditions: a mean systolic blood pressure of greater than or equal to 130 millimeters of mercury, a mean diastolic blood pressure of greater than or equal to 80 millimeters of mercury, or taking a medication to lower blood pressure. Again, the blood pressure measurements were taken using an oscillometric protocol. During 2017 through March 2020, 45.1% of adults had hypertension. More men had hypertension then woman. Hypertension increased with increasing age. And Non-Hispanic Black adults had a higher prevalence of hypertension than other race and Hispanic origin groups.

We found that 41.9% of adults had obesity, defined as a body mass index greater than or equal to 30 kilograms per meter squared. There was no difference in obesity by sex or by age. Non-Hispanic Black adults had the highest prevalence of obesity. Non-Hispanic Asian adults had a lower prevalence of obesity than other race and Hispanic origin groups.

Severe obesity was defined here as a body mass index of greater than or equal to 40 kilograms per meter squared. During 2017-from-March 20, 9.2% of adults had severe obesity. More women had severe obesity than men. Severe obesity was less common in those aged 60 and above, compared to those aged 20 to 39, and those aged 40 through 59. The prevalence of severe obesity was highest among non-Hispanic Black adults, and the least among non-Hispanic Asian adults. Severe obesity was lowest among those with a family income of greater than 350% of the federal poverty level.

Diabetes was defined here as having previously been given a diagnosis of diabetes, having a fasting plasma glucose of greater than or equal to 126 milligrams per deciliter, or having a hemoglobin A1C greater than or equal to 6.5%. Fasting sample weights were used to calculate these estimates.

14.8% of adults had diabetes. The prevalence of diabetes was higher among men than women. The prevalence of diabetes increased with increasing age but decreased with increasing family income and the prevalence of diabetes was lower in non-Hispanic White adults compared to other race and Hispanic origin groups.

Complete tooth loss among adults aged 65 years and older was defined here as having no natural tooth, dental root fragment nor implanted tooth and was based on 28 teeth, excluding third molars. The prevalence of complete tooth loss was 13.8%. The prevalence did not differ by sex but did increase with age. Tooth loss was higher among non-Hispanic Black adults than non-Hispanic White adults but otherwise did not differ by race and Hispanic origin and tooth loss decreased with increasing family income.

So with regards to the future, more data releases are anticipated. These data releases will occur in several different forms. Other combined 2017-through-March 2020 pre-pandemic data are expected to be released on the NHANES website and would be treated like a probability sample. And provided sample weights should be used for analysis with these data.

In the future, this data would be released on the NHANES website along with the currently available data, which can be found under the NHANES 2017 through March 2020 Pre-pandemic data page.

In some cases, 2017-through-March 2020 pre-pandemic data determined to have disclosure risk will be released through the NCHS Research Data Center to ensure additional measures to protect confidentiality. For these data, which are treated like a probability sample, the provided sample weights should also be used for analyses.

For those data released as limited access data files, once released, information about the variables will be available on the NHANES website under limited-access files, under the 2017-to-March 2020 Pre-pandemic data page. However, the actual data will only be available through NCHS’s Research Data Center.

There are some measures that are unique to the 2019-through-March 2020 NHANES data collection. These cannot be combined with 2017-through-2018. And, for these measures, nationally representative estimates are not possible. These data will instead be released through the NCHS Research Data Center.

For these data, released as limited access data files, once released, information about the variables will be available on the NHANES website under limited-access files under the 2019-through-2020 data page. However, again, the actual data will only be available through NCHS’s Research Data Center.

And this can be found on the NCHS website. Information about accessing restricted data, including submission of research proposals, can be found here. Thank you.

HOST:  May has been a busy month, one in which several milestones were observed through NCHS data.  On May 11, full-year 2021 provisional data was released on drug overdose deaths in the country.  Drug deaths topped 107,000 last year, and fentanyl and other synthetic opioids were involved in two-thirds of those deaths.  Overdose deaths increased 15% in 2021, which was half the increase observed in 2020, when overdose deaths increased 30% from 2019.  In 2021, Alaska saw the biggest increase in overdose deaths – a 75% increase for the year.  Hawaii was the only state to have a decline in overdose deaths – a 1.8% drop from 2020.

On May 16, the United States reached a tragic milestone, topping the one million death mark for  COVID-related deaths since January 2020.  COVID-19 remains the 3rd leading cause of death for all Americans.

This month NCHS also documented that the number and rate of marriages in the U.S. during 2020 fell over 16% from 2019, and the number of marriages was the lowest in the country since 1963.  46 states and DC saw declines in marriage during 2020, and only four states – Montana, Utah, Texas, and Alabama – saw their marriage rates increase during 2020.  Nevada, as usual, had the highest marriage rate in the country during 2020 – but the rate dropped nearly 19% from 2019.

On May 24, NCHS released 2021 birth statistics for the nation, showing the first increase in the number of births and the general fertility rate in seven years.  The general fertility rate is the number of births per 1,000 women ages 15 to 44.  The teen birth rate continued to drop in 2021, marking the 28th year in the last 30 years that the birth rate for females ages 15-19 has declined.  While birth rates dropped in 2021 for women between ages 15 and 24, rates increased for women between ages 25 and 49.  Meanwhile, cesarean deliveries increased in 2021, and preterm birth rates also increased, to the highest level since 2007.

And last, NCHS released a report on sexual orientation and differences in access to care, health status, behaviors and beliefs.  The new study drew from three different NCHS data sources:  the National Health and Nutrition Examination Survey, the National Health Interview Survey, and the National Survey of Family Growth.  The research found that bisexual men and women, gay men, and lesbian women report smoking and heavy drinking and using marijuana and illicit stimulants more often than heterosexual people.  Lesbian and bisexual women reported diagnoses of arthritis, asthma, cancer, diabetes, heart disease, and hypertension more often than heterosexual women.  Bisexual women reported having been diagnosed with endometriosis, ovulation or menstrual problems, and pelvic inflammatory disease more often than heterosexual women.  Weight and other body measurements also differed by sexual orientation.

Thank you for tuning in to this month’s edition of “Statcast…”

https://www.cdc.gov/nchs/pressroom/podcasts/2022/20220422/20220422.htm

(Based on the June 16, 2021, webinar, National Health and Nutrition Examination Survey 2017–March 2020 Pre-pandemic Data Release )

HOST: NHANES – the National Health and Nutrition Examination Survey – is designed to assess the health and nutritional status of adults and children in the United States. The survey uses complex sampling design to ensure that the data collected are nationally representative. And it also combines information collected across several different survey components. During a home interview, participants provide information on demographic characteristics, health conditions, and risk factors and behaviors, such as which dietary supplements and prescription medications they are using. Then, participants are invited to travel to a nearby mobile examination center to participate in a health exam, in which they undergo tests, provide lab specimens, and take part in additional interviews. After the exam, participants may be contacted again to participate in post-exam content. This could include activities such as dietary recall, interviews, or wearing a physical activity monitor. The survey content varies over time and covers a wide variety of health conditions and public-health topics. Conducting examinations, along with health interviews, provides data that is invaluable for public health. But it also poses operational and statistical challenges.

Dr. Lara Akinbami, a pediatrician and medical officer with the Division of Health and Nutrition Examination Surveys at NCHS, discussed some of those challenges in a webinar last year:

AKINBAMI: NHANES is conducted in 15 sites per year due to the intricate field operations of the survey. The mobile exam centers, or MECs, must be driven to each new site and set up and maintained according to exact specifications. Teams includes interviewers, clinicians, technicians, and engineers live in the field full time as they travel among the different survey locations over the year. Each MEC contains a mobile laboratory with all the equipment needed for specimen processing and storage until specimens can be shipped to laboratories for testing. On-site testing is also performed for some health measures to provide immediate results to participants. There’s also other equipment for medical testing in the MECs. For example, a spirometer has been used to measure lung function and a sound-isolating room is used to test hearing. Depending on which health exams and measures are being performed, equipment can be swapped in and out of the MECs. The range of pre-pandemic activities that occurred in the MECs was broad. These included body measures, such as weight and height, Blood-pressure measurements, DEXA scans to assess bone density, oral health exams, and phlebotomy and urine collection to collect specimens for a wide array of lab tests. In addition, participants responded to additional interviews, such as audio computer-assisted self-interviews for more sensitive topics that included reproductive health and alcohol and substance use. The MECs provide a way to standardize protocols, equipment, and exam environments across different locations and across time, so that results are comparable. This allows for more accurate interpretation of health differences between groups and of trends over time. NHANES began continuous field operations in 1999.

And, although data collection continued from year to year, data were released in two-year cycles. Each two-year cycle is drawn from a multiyear sample design. These sample designs have changed over time to keep up with changes in the U.S. population. For instance, the 2015-to-2018 sample design selected 60 locations to be visited over four years. The 2015-to-2016 data-collection cycle visited the other 30. Although data are available for two-year cycles, NHANES advises combining cycles together into four-year data sets to calculate reliable estimates for subgroups. For example, estimating the prevalence of a health condition by age group separately for men and women, or for race and Hispanic-origin groups among children, is best done with a four-year data set.

HOST: Dr. Akinbami also discussed in the webinar how the pandemic impacted NHANES data collection.

AKINBAMI: So, like almost everything else, NHANES was affected by the COVID-19 pandemic. The 2019-to-2022 sample design also chose 60 locations to be sampled over four years. NHANES entered the field in 2019 with a plan of visiting the first 30 locations in the 2019-to-2020 data collection cycle. In March 2020, a growing number of cases of COVID-19 disease were being reported to CDC. This suggested that community spread was occurring. Widespread shutdowns had not yet occurred, but the environment was starting to change. For example, mobility data show that, during March, normal patterns and movements started to decline. The NHANES program needed to decide whether continuing field operations posed a risk of coronavirus transmission to participants and staff and their close contacts. On March 16, field operations for NHANES were suspended. And, although it wasn’t clear at the time, this meant that the 30 locations planned for the 2019-to-2020 cycle would not all be visited. When field operations were stopped in March of 2020, the survey had been to 18 of 30 planned locations. And, as 2020 progressed, it was clear that there was no feasible way to resume in-person exams. The potentially long pause before field operations could be resumed raised questions about how a break in data collection would affect estimates of health conditions. Resuming data collection when it was safe to do so would mix pre-pandemic data and pandemic data together and potentially introduce bias into the estimates, especially for a two-year cycle that would have to be extended.

Therefore, it was decided not to collect more data for this cycle. Because no additional data would be collected, the 2019-to-March 2020 sample was not nationally representative. There was no method to create sample weights using the 2019-to-2022 sample design. Additionally, publicly releasing the data for fewer than 30 locations could pose disclosure risks for participants. However, the data that were collected represented a significant investment by survey participants, the federal government, and collaborators; and simply not using the data wasn’t an option. So, a solution was found in the creation of a pre-pandemic data file. The 2017-to-2018 two-year cycle contained a complete sample and was nationally representative. It could be used to build a larger data set. And methodology to combine a probability sample with a nonprobability sample was used but adapted to this situation. The probability sample in this case was the 2017-to-2018 sample. And, rather than a nonprobability sample, the2019-to-March 2020 sample was a partial probability sample, because it was selected based on the 2019-to-2022 sample design.

So here’s an overview of how a 2017-to-March 2020 pre-pandemic data set was created and some analytic considerations when working with the data. The 2015-to-2018 sample design specified the locations chosen for the 2017-to-2018 data collection cycle. And, as we mentioned previously, all 30 locations were visited in 2017 to 2018. The 2019-to-2022 sample design specified 30 locations that were supposed to have been visited in the 2019-to-2020 data collection cycle and only 18 were visited. Combining the 2017-to-2018 sample with the 2019-to-March 2020 sample posed a problem. The 2015-to-2018 and the 2019-to-2022 sample designs were different because the 2019-to-2022 sample design was updated to reflect the changing United States. So the chosen solution was to pick one of these sample designs. Because the 2017-to-2018 data collection cycle fully adhered to the 2015-to-2018 sample design, this design was chosen. The 18 sites that were visited in 2019 to March 2020 were reassigned to the 2015-to-2018 sample design. Now that a design was chosen, the sample weights could be calculated. However, there were still some issues that needed to be resolved. The 2019-to-March 2020 locations didn’t line up exactly with the 2015-to-2018 sample design. The result was that some portions of the country were underrepresented in the data. An adjustment factor was used to equalize representation over the sites visited from 2017 to March 2020. And, once that was done, interview weights and exam weights were then calculated using previous methodology. Extensive assessments confirmed that the final sample was nationally representative by making demographic comparisons to the American Community Survey, which is a population survey administered by the U.S. Census.

HOST: Dr. Akinbami concludes by discussing some important analytic considerations for users of the data.

AKINBAMI: The resulting 2017 to March 2020 pre-pandemic data can be used to calculate nationally representative estimates of health conditions and behaviors. It can be used as the previously released data sets for two-year cycles. However, the data from the partial 2019-to-March 2020 cycle by themselves are not nationally representative.

Therefore 2017-to-2018 data cannot be compared to the 2019-to-March 2020 data. And remember that, because the 2019-to-March 2020 data did not conform to the 2019-to-2020 survey design, no separate survey weights could be constructed for this cycle. It is not appropriate to use the 2017-to-March 2020 pre-pandemic weights for the partial sample collected in 2019 to March 2020. The weight adjustment that was applied to the 2017-to-March 2020 data was designed for overall estimates but not necessarily for subgroups. So, therefore, when 2017-to-March 2020 estimates for subgroups are compared to earlier estimates, trends should be interpreted with caution. For example, when the adjustment factor and other measures were applied to the survey weights, national representation by sex

was achieved and so is representation by age. But some sex-specific age

groups, for example, may have larger variation in estimates depending on how the participants are distributed across survey locations.

MUSICAL BRIDGE

HOST: In part two of this feature on pre and post-pandemic NHANES, Dr. Bryan Steirman discusses a published report on health estimates from this NHANES data set.  This webinar is accessible on the NCHS website.

HOST:  On April 12, NCHS released its quarterly mortality data on several leading causes of death, with disease-related mortality rates featured through the third quarter of 2021.  The web feature “Stats of the States” was also updated the same day.  “Stats of the States” features key vital statistics on topics such as Births, Deaths, and Marriages & Divorces by state.  Users can rank States according to rates, either highest to lowest or lowest to highest.  This data visualization was updated with final 2020 data for all these measures.  Included in each State fact sheet are the 10 leading causes of death for each state, which always presents some interesting variation from state to state.  2020, of course, features the introduction of COVID-19 as the 3rd leading cause of death in the U.S.  And at the state level, COVID-19 indeed was the 3rd leading cause of death in 44 states and DC.  As for the other states, COVID was 4th among the leading killers in 3 states:  Alaska, New Hampshire, and Utah.  The virus was the 5th leading cause of death in 2 states:  Washington and West Virginia., as well as the 7th leading cause of death in 2 states:  Hawaii and Oregon, and the 8thth leading cause of death in 2 states:  Maine and Vermont.  Provisional data for 2021 suggests some changes to those rankings, based on regional outbreaks of the virus.

Finally, on April 20th, NCHS released a new report comparing dental utilization rates among adults in 2019 with the arrival of the pandemic in 2020.

Next month promises to be a more active month of data releases for NCHS, including full-year 2021 drug overdose death data, full-year 2021 birth data, and a new report on sexual orientation differences in access to care and health status, behaviors and beliefs.

MUSIC OUT