National Health Interview Survey

NHIS at a Glance

NHIS at a Glance
National Health Interview Survey
Data Type National self-report survey
Sample Nationally representative sample
VEHSS Topics Included
  • Visual Function
  • Eye Health Conditions
  • Service Utilization
Years Analyzed 2014/15 merged, 2016/17 merged
Approximate Size Approximately 87,500 people per year

The main objective of the National Health Interview Survey (NHIS) is to monitor the health of the United States population through the collection and analysis of data on a broad range of health topics. The survey has been conducted since 1957, and since 1960 has been conducted by National Center for Health Statistics (NCHS). NHIS data are used widely by the Department of Health and Human Services (DHHS) and the public health research community to monitor trends in illness and disability and to track progress toward achieving national health objectives. NHIS was selected for inclusion in VEHSS due to its wide range of vision-related questions, as well as its inclusion of all three risk factor variables of interest.

Sample Design

The National Health Interview Survey is a cross-sectional household interview survey of the noninstitutionalized US population. Each year, the sample contains approximately 35,000 households and 87,500 individuals. Sampling and interviewing occurs continuously throughout the year. The sampling plan follows a multistage area probability design that permits the representative sampling of households and noninstitutional group quarters (e.g., college dormitories). The sampling plan was redesigned most recently in 2016.

The first stage of the 2006-2015 sampling plan consists of selecting a sample of 428 primary sampling units (PSU’s) drawn from approximately 1,900 geographically defined PSU’s that cover the 50 States and the District of Columbia. Nearly all states have at least two PSUs selected for the sample, with most having notably more. For each PSU, there are two second-stage units—area segments which are defined geographically, and permit segments which cover housing units built after the 2000 census. The NHIS sampling frame consists of the area and permit frames, which consist of all of the area and permit segments, respectively. This sampling design includes the oversampling of black, Asian, and Hispanic people.

The total NHIS sample is subdivided into four separate panels, or sub-designs, such that each panel is a representative sample of the U.S. population. For 2006-2010, the households and noninstitutional group quarters selected for interview each week are a probability sample representative of the target population. Beginning in 2011, the minimum time length for a probability sample changed from a week to a month.

2016-2018 Sampling Plan

A new sample design was implemented with the 2016 NHIS. Sample areas were reselected to take into account changes in the distribution of the U.S. population since 2006, when the previous sample design was first implemented. Commercial address lists were used as the main source of addresses, rather than field listing; and the oversampling procedures for Black, Hispanic, and Asian persons that were a feature of the previous sample design were not implemented in 2016.

The first stage of the current sample design consists of a sample of 319 primary sampling units (PSUs) drawn from approximately 1,700 geographically defined PSUs, with some PSUs in each of the 50 states and the District of Columbia.

The NHIS sampling frame consists of three non-overlapping parts: the unit frame (a list of addresses purchased from a vendor); the area frame (geographic areas that do not have city-style addresses, and geographic areas where the unit frame was not considered to be a sufficient sampling resource); and the college dormitory frame (college residence hall spaces in the NHIS sample PSUs). As with the earlier sample designs, the total NHIS sample is subdivided into four separate panels such that each panel is representative of the U.S. civilian noninstitutionalized population (as is any combination of the four panels).

Data Collection Procedures

NHIS data are collected via an in-person household interview conducted by interviewers who are employed and trained by the U.S. Census Bureau. Since 1997, the NHIS questionnaire has been administered in the computer assisted personal interviewing (CAPI) mode. The questionnaire is administered with a laptop computer, with interviewers entering responses directly during the interview.

For the Household Composition section, one household member who is at least the age of legal majority for the state of residence is identified as the household respondent. The household respondent provides basic demographic and relationship information about all household members; these relationships determine the number of families that comprise the household. For the Family core component, all adult members of the household who are 18 years and older and at home during the time of the interview are invited to participate and respond for themselves, however a family respondent may respond for all children and adults in the family. If a child or adult is not home during the interview, a responsible adult family member who is 18 years or older and resides in the household can provide the answers. For the Sample Adult questionnaire, one civilian adult per family is randomly selected to be interviewed. Similarly, a child is randomly selected for the Sample Child questionnaire. Information for this questionnaire is provided by an adult knowledgeable about the child’s health.[1]

Analysis Overview

We estimated the prevalence rate and sample size for each survey instrument selected for inclusion. We merged samples from the 2014 and 2015 rounds and then the 2016 and 2017 rounds for analysis in order to maximize the available sample sizes at more detailed levels of stratification.  This partition corresponds to the new sampling frame, as well as more vision-related questions were fielded in 2016-2017. New weights were created by dividing the original weights by two [2].

For binary response questions included in the analysis, prevalence rate was defined as the number of persons who gave an affirmative response to the question divided by the total number of respondents who gave an affirmative or negative response and then multiplied by 100 for presentation in percentage format.  For scaled responses, the data value is the proportion of respondents that selected any one of the possible response option, and all responses should sum to 100%. We estimated upper and lower confidence intervals and the relative standard error of the prevalence estimate using the Clopper-Pearson method with the smaller of the effective sample size and the sample size. The respondent sample size was reported for each response.

All estimates were calculated using SAS proc survey freq. Suppression was determined using the National Center for Health Statistics Data Presentation Standards for Proportions released in August 2017 [3].

A detailed description of the analytical steps is described in the report “VEHSS Survey Analysis Plan pdf icon[PDF – 480 KB]external icon.”  Full analysis documentation is included in the “VEHSS NSCH Data Report pdf icon[PDF – 568 KB]external icon.”

Variables Analyzed in VEHSS

Across all the NHIS core and supplemental questionnaires, there were 16 vision-related questions during 2014-2015 period. For the 2016-2017 period, there were 46 vision-related questions. Many of these questions are duplicative of one another, as the same question may be asked of two different target populations—e.g., children and adults–in two different questionnaires. For the 2014-2015 analyses, we prioritized the six questions that provide an understanding of the prevalence of visual impairment in children and adults. For the 2016-2017 analyses, with the increase in the number of questions, we included questions from the child and adult sample files that asked about service utilization in addition to those that provide an understanding of the prevalence of visual impairment. Questions we have not yet included in these analyses focus on access to vision-related healthcare and aids and duration of vision problems.

Child Questionnaire

We analyzed eight questions from the child sample file, six of those questions are asked with the same or very similar wording in the adult sample questionnaire. Two of the questions were asked all four years while the other six were only asked in 2016-2017. Five questions were categorized under the ‘Service Utilization’ Topic and three under the ‘Visual Function’ Topic. Each ‘Visual Function’ Topic question fell into its own category –‘Blind of Difficulty Seeing’, ‘Difficulty Seeing with Glasses,’ and ‘Vision Correction’.

Adult Sample Questionnaire

We analyzed 18 questions from the adult sample file, covering three Topics areas – ‘Visual Function’, ‘Eye Health Conditions’, and ‘Service Utilization’. Six of the nine ‘Visual Function’ questions asked about difficulty performing a range of routine activities and fell into the ‘Far-Distance Visual Function’, ‘Night Vision’, ‘Miscellaneous Life Impact’, ‘Near-Distance Visual Function’, and ‘Peripheral Visual Function’ categories. The other three ‘Visual Function’ questions each fell into their own categories– ‘Difficulty Seeing with Glasses’, “Blind or Difficulty Seeing’, and ‘Vision Correction’. The four ‘Eye Health Conditions’ questions asked respondents whether a doctor ever told them they had diabetic retinopathy, cataracts, glaucoma, or macular degeneration. The five ‘Service Utilization’ question were related to eye exam with dilation, cataract surgery, use of eye protection when participating in potential eye-injury-causing  activities, and interacting with an eye health provider. The functioning and disability questionnaire was administered to approximately half of the adult sub-sample, via random selection through 2017. In 2018 the functioning and disability questions are being asked to the entire adult sample. Table 1 presents additional details about these questions,  including the VEHSS Topic and Category, the NHIS variable name, the year(s) survey data are available, the survey question, and the response options. The table also includes the universe included in the question as there were several questions that had follow-up questions if the response was ‘Yes’ to the main question.

Table 1. NHIS Variables analyzed in VEHSS

Overview of NHIS Variables Included in VEHSS
VEHSS Indicator Topic VEHSS Indicator Category NHIS Variable Name Years Available1 Question Universe Response Options
Sample Child File
Visual Function Blind or Difficulty Seeing CVISION 1999-2018 Does [NAME] have any trouble seeing, even when wearing glasses or contact lenses? Sample children <18 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Visual Function Blind of Difficulty Seeing CBLIND 1999-2018 Is [NAME] blind or unable to see at all? Sample children <18 who said Yes to CVISION 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Eye Exams CVISTST 2016-2017 Has [NAME] EVER had [his/her] vision tested by a doctor or other health professional? Sample children <6 who are not blind 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Eye Exams CVISLT 2016-2017 When was [his/her] vision last tested? Sample children <6 who said Yes to CVISTST 1 in the last 12 month
2 in the last 13-24 months
3 Over 24 months
7 Refused
8 Not ascertained
9 Don’t know
Visual Function Vision Correction CVISGLAS 2016-2017 Does [NAME] wear eyeglasses or contact lenses? Sample children 6-17 who are not blind 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Use of eye protection CVISACT 2016-2017 Does [NAME] participate in sports, hobbies, or other activities that can cause eye injury? This includes activities such as baseball, basketball, soccer and mowing the lawn. Sample children 6-17 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Use of eye protection CVISPROT 2016-2017 When doing these activities, on average, does [he/she] wear eye protection always, most of the time, some of the time, or none of the time? Sample children 6-17 who said YES to CVISACT 1 Always
2 Most of the time
3 Some of the time
4 None of the time
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Eye Health Provider Interaction

CHCSYR11

CHCSYR2

2016-2018

DURING THE PAST 12 MONTHS, has anyone in the family seen or talked to any of the following health care providers about [NAME]’s health?

An optometrist, ophthalmologist, or eye doctor (someone who prescribes eyeglasses)?

Sample children <18 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Sample Adult File
Visual Function Difficulty Seeing with Glasses AVISION 1999–2016 Do you have any trouble seeing, even when wearing glasses or contact lenses? Sample Adult 18+ 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Visual Function Blind of Difficulty Seeing ABLIND 1999–2016 Are you blind or unable to see at all? Sample adults 18+ who said Yes to AVISION 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Eye Health Conditions Self-Report Diabetic Retinopathy VIM_DREV 2016-2017 Have you EVER been told by a doctor or other health professional that you had Diabetic retinopathy? Sample Adult 18+ 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Eye Health Conditions Self-Report Cataract VIM_CAEV 2016-2017 Have you EVER been told by a doctor or other health professional that you had Cataracts? Sample Adult 18+ 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Cataract Surgery VIMCSURG 2016-2017 Have you ever had cataract surgery? Sample Adult 18+ who said Yes to VIM_CAEV 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Eye Health Conditions Self-Report Glaucoma VIM_GLEV 2016-2017 Have you EVER been told by a doctor or other health professional that you had glaucoma Sample Adult 18+ 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Eye Health Conditions Self-Report Age Related Macular Degeneration VIM_MDEV 2016-2017 Have you EVER been told by a doctor or other health professional that you had Macular Degeneration? Sample Adult 18+ 1 Yes
2 No
7 Refused
8 Not ascentained
9 Don’t know
Visual Function Vision Correction VIMGLASS 2016-2017 Do you currently wear eyeglasses or contact lenses? Sample Adult 18+ who said No to ABLIND 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Visual Function Far-Distance Visual Function AVDF_NWS 2016-2017

Even when wearing glasses or contacts lenses, because of your eyesight, / Fill 2: Because of your eyesight,] how difficult is it for you

…To read ordinary print in newspapers

Sample Adult 18+ who said No to ABLIND 0 Not at all difficult
1 Only a little difficult
2 Somewhat difficult
3 Very difficult
4 Can’t do at all because of eyesight
6 Do not do this activity for other reasons
8 Not ascertained
9 Don’t know
Visual Function Far-Distance Visual Function AVDF_CLS 2016-2017

Even when wearing glasses or contacts lenses, because of your eyesight, / Fill 2: Because of your eyesight,] how difficult is it for you

…To do work or hobbies require you to see well up close such as cooking, sewing, fixing things around the house or using hand tools

Sample Adult 18+ who said No to ABLIND 0 Not at all difficult
1 Only a little difficult
2 Somewhat difficult
3 Very difficult
4 Can’t do at all because of eyesight
6 Do not do this activity for other reasons
8 Not ascertained
9 Don’t know
Visual Function Night Vision AVDF_NIT 2016-2017

Even when wearing glasses or contacts lenses, because of your eyesight, / Fill 2: Because of your eyesight,] how difficult is it for you

…To go down steps, stairs, or curbs in dim light or at night

Sample Adult 18+ who said No to ABLIND 0 Not at all difficult
1 Only a little difficult
2 Somewhat difficult
3 Very difficult
4 Can’t do at all because of eyesight
6 Do not do this activity for other reasons
8 Not ascertained
9 Don’t know
Visual Function Miscellaneous Life Impact AVDF_CRD 2016-2017

Even when wearing glasses or contacts lenses, because of your eyesight, / Fill 2: Because of your eyesight, ] how difficult is it for you

…To find something on a crowded shelf

Sample Adult 18+ who said No to ABLIND 0 Not at all difficult
1 Only a little difficult
2 Somewhat difficult
3 Very difficult
4 Can’t do at all because of eyesight
6 Do not do this activity for other reasons
8 Not ascertained
9 Don’t know
Visual Function Near-Distance Visual Function AVDF_DRV 2016-2017

Even when wearing glasses or contacts lenses, because of your eyesight, / Fill 2: Because of your eyesight,] how difficult is it for you

…To drive during daytime in familiar places

Sample Adult 18+ who said No to ABLIND 0 Not at all difficult
1 Only a little difficult
2 Somewhat difficult
3 Very difficult
4 Can’t do at all because of eyesight
6 Do not do this activity for other reasons
8 Not ascertained
9 Don’t know
Visual Function Peripheral Visual Function AVDF_PER 2016-2017

Even when wearing glasses or contacts lenses, because of your eyesight, / Fill 2: Because of your eyesight,] how difficult is it for you

…To notice objects off to the side while you are walking along

Sample Adult 18+ who said No to ABLIND 0 Not at all difficult
1 Only a little difficult
2 Somewhat difficult
3 Very difficult
4 Can’t do at all because of eyesight
6 Do not do this activity for other reasons
8 Not ascertained
9 Don’t know
Service Utilization Eye Exams AVISEXAM 2016-2017 When was the last time you had an eye exam in which the pupils were dilated? This would have made you temporarily sensitive to bright light. Sample Adult 18+ who said No to ABLIND 1 Less than one month
2 1-12 months
3 13-24 months
4 More than 2 years
5 Never
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Use of eye protection AVISACT 2016-2017 Outside of work, do you participate in sports, hobbies, or other activities that can cause eye injury? This includes activities such as baseball, basketball, mowing the lawn, wood working, or working with chemicals. Sample Adult 18+ 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Use of eye protection AVISPROT 2016-2017 When doing these activities, on average, do you wear eye protection always, most of the time, some of the time, or none of the time? Sample Adult 18+ who said Yes to AVISACT 1 Always
2 Most of the time
3 Some of the time
4 None of the time
7 Refused
8 Not ascertained
9 Don’t know
Service Utilization Eye Health Provider Interaction AHCSYR2 2016-2018

DURING THE PAST 12 MONTHS, have you seen or talked to any of the following health care providers about your own health?

…An optometrist, ophthalmologist or eye doctor (someone who prescribes eyeglasses).

Sample Adult 18+ 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know
Functioning and Disability File
Visual Function Difficulty Seeing with Glasses VIS_SS22 2011-2018 Do you have difficulty seeing, even when wearing glasses? Sample adults 18+ who were asked the family disability questions (FDB) and were randomly selected to receive the Functioning and Disability (AFD) section 1 No difficulty
2 Some difficulty
3 A lot of difficulty
4 Cannot do at all/unable to do
7 Refused
8 Not ascertained
9 Don’t know
Visual Function Vision Correction VIS_02 2012–2018 Do you wear glasses? Sample adults 18+ who were asked the family disability questions (FDB) and were randomly selected to receive the Functioning and Disability (AFD) section 1 Yes
2 No
7 Refused
8 Not ascertained
9 Don’t know

Table 2 presents the sample sizes for analysis by coded response option for the variables included in this report. The 2016-2017 functioning and disability questions were used for internal validation purposes.

Table 2. Frequency of coded response options for analyzed variables for 2014-2015
Variable Response Sample Size
Sample Child File
CVISION
CBLIND
Yes 655 (CBLIND Yes 31, No 621, Missing 3)
No 24,988
Missing 28
CHCSYR11
CHCSYR2
Not analyzed Not analyzed
Sample Adult File
AVISION
ABLIND
Yes 7202 (ABLIND Yes 309, No 6,890, Missing 3)
No 63,130
Missing 37
Functioning and Disability File
VIS_SS2 No difficulty 27,894
Some difficulty 4,842
A lot of difficulty 605
Cannot do at all/unable to do 69
Refused 73
Not ascertained 1,741
Don’t know 18
VIS_0 Yes 2,099
No 12,429
Missing 1,823
Table 2. Frequency of coded response options for analyzed variables for 2016-2017
Variable Response Sample Size
Sample Child File
CVISION
CBLIND
Yes 661 (CBLIND Yes 30, No 631, Missing 0)
No 19,270
Missing 21
CVISTST     CVISLT Yes 2997 (CVISLT In the last 12 months 2,492, In the last 13-24 months 357, Over 24 months 126, Don’t Know 22, Missing 0)
No 3,367
Missing 103
CVISGLAS Yes 4,472
No 8,981
Missing 2
CVISACT
CVISPROT
Yes 5,943 (CVISPROT Always 1,020, Most of the time 418, Some of the time 676, None of the time 3,812, Refused 1, Don’t know 16, Missing 0)
No 7,527
Missing 9
CHCSYR11  CHCSYR2 Yes 5,455
No 14,386
Missing 111
Sample Adult File
AVISION
ABLIND
Yes 7,030 (ABLIND Yes 265, No 6,765, Missing 0)
No 52,721
Missing 0
VIM_DREV Yes 613
No 59,067
Missing 90
VIM_CAEV
VIMCSURG
Yes 10,767 (VIMCSURG Yes 6,467, No 59,067, Missing 4)
No 48,935
Missing 68
VIM_GLEV Yes 1,996
No 57,687
Missing 87
VIM_MDEV Yes 1,480
No 58,174
Missing 116
VIMGLASS Yes 40,379
No 19,117
Missing 274
AVDF_NWS Not at all difficult 47,881
Only a little difficult 6,474
Somewhat difficult 3,161
Very difficult 1,274
Can’t do at all because of eyesight 318
Do not do this activity for other reasons 370
Refused 8
Not ascertained 0
Don’t know 19
Missing 265
AVDF_CLS Not at all difficult 50,819
Only a little difficult 4,704
Somewhat difficult 2,343
Very difficult 829
Can’t do at all because of eyesight 222
Do not do this activity for other reasons 551
Refused 9
Not ascertained 0
Don’t know 28
Missing 265
AVDF_NIT Not at all difficult 52,206
Only a little difficult 3,062
Somewhat difficult 1,987
Very difficult 975
Can’t do at all because of eyesight 200
Do not do this activity for other reasons 1,044
Refused 12
Not ascertained 0
Don’t know 19
Missing 265
AVDF_CRD Not at all difficult 55,612
Only a little difficult 1,964
Somewhat difficult 1,080
Very difficult 409
Can’t do at all because of eyesight 92
Do not do this activity for other reasons 310
Refused 12
Not ascertained 0
Don’t know 26
Missing 265
AVDF_DRV Not at all difficult 53,527
Only a little difficult 1,161
Somewhat difficult 1,987
Very difficult 194
Can’t do at all because of eyesight 282
Do not do this activity for other reasons 3,781
Refused 11
Not ascertained 0
Don’t know 14
Missing 265
AVDF_PER Not at all difficult 55,824
Only a little difficult 1,619
Somewhat difficult 999
Very difficult 419
Can’t do at all because of eyesight 156
Do not do this activity for other reasons 418
Refused 11
Not ascertained 0
Don’t know 59
Missing 265
AVISEXAM Less than one month 3,445
1-12 months 23,577
13-24 months 9,520
More than 2 years 15,322
Never 7,149
Refused 20
Not ascertained 0
Don’t know 737
Missing 0
AVISACT   AVISPROT Yes 14,842 (AVISPROT Always 4,770, Most of the time 2,291, Some of the time 2,850, None of the time 4,918, Refused 1, Not ascertained 0, Don’t know 3)
No 44,908
Missing 20
AHCSYR2 Yes 26,544
No 32,549
Missing 677
Functioning and Disability File
VIS_SS2 No difficulty 24,289
Some difficulty 4,060
A lot of difficulty 414
Cannot do at all/unable to do 49
Refused 26
Not ascertained 954
Don’t know 11
VIS_0 Yes 19,616
No 9,211
Missing 976

Stratification Variables

All variables from the sample child file (CVISION, CBLIND, CVISTST, CVISLT, CVISGLAS, CVISACT, CVISPROT, and CHCSYR11/CHCSYR2 ) were stratified by age, sex, and race/ethnicity. The variables from the sample adult (AVISION, ABLIND, VIM_DREV, VIM_CAEV, VIMSURG, VIM_GLEV, VIM_MDEV, VIMGLASS, AVDF_NWS, AVDF_CLS, AVDF_NIT, AVDF_CRD, AVDF_DRV, AVDF_PER, AVISEXAM, AVISACT, AVISPROT, AHCSYR2) and 2014-2015 functioning and disability files (VIS_SS2, VIS_0) were stratified by age, sex, and race/ethnicity, diabetes status, hypertension status, and smoking status. Ages (variable: AGE_P) ranged from 0 to 17 years for participants in the sample child file, and from 18 to 85+ in the sample adult and functioning and disability files. Participant sex (variable: SEX) was coded as Male or Female. The Hispanic and race variables (variables: HISPAN_I and RACERPI2) were combined to create a single race/ethnicity variable, with anyone identifying as Hispanic being placed in a single category. The race categories were coded as follows: Non-Hispanic Asian, Non-Hispanic Black, Hispanic, Non-Hispanic North American Native, Non-Hispanic Other, and Non-Hispanic White. The ‘Other’ category consists of those whose race was not releasable due to issues of confidentiality, as well as those who identify with multiple racial categories. Diabetes status (variable: DIBEV) was recoded into ‘Yes,’ ‘No,’ and ‘Borderline’; Hypertension status (HYPEV) as ‘Yes’ and ‘No’; and Smoking status (SMKSTAT2) as ‘Current,’ ‘Former,’ and ‘Never.’ State identifiers are not released in NHIS public use files due to confidentiality concerns. Stratification variables and their frequencies are listed below.

Stratification variable frequencies
Variables Frequency
2014-2015 2016-2017
Sample Child File Sample Adult File Functioning and Disability File Sample Child File Sample Adult File
AGE
0-17 years 25671 19952
18-39 years 24069 12009 19226
40-64 years 29278 14649 24308
65-84 years 14774 7440 14190
85 years and older 2248 1144 2046
SEX
Male 13137 31469 15778 10351 27087
Female 12534 38900 35242 9601 32683
RACE/ETHNICITY
Non-Hispanic White 11928 43634 21844 10983 41720
Non-Hispanic Black 3475 9359 4660 2272 6397
Hispanic, any race 7342 11644 5843 4390 7050
Asian 11928 3907 1960 1080 2919
Non-Hispanic Other 1227 1309 671 1016 1176
North American Native 222 516 264 211 508
DIABETES
Yes 7471 3717 6331
Borderline 1183 598 1679
No 61670 30904 51706
Missing 45 23 54
HYPERTENSION
Yes 24141 12204 21054
No 46138 22995 38631
Missing 90 43 85
SMOKING
Current Smoker 11793 5836 9355
Former Smoker 16060 8045 14754
Never Smoker 42185 21188 35438
Missing 331 173 223

Stratification Levels Included in the Full Analysis

The full analysis includes additional stratifications beyond those included in this data summary report, and will be made available on the VEHSS project website.  We stratified data using all possible combinations of age, race/ethnicity, sex, and risk factor at the national level. All stratifications are displayed in Table 4.

Stratification Level Stratification Factor
Table 4. Stratification Factor Combinations Included in Full Results
0-level All participants
1-level Age
Race/Ethnicity
Sex
Diabetes
Hypertension
Smoking
2-level Age* Race/Ethnicity
Age*Sex
Race/Ethnicity *Sex
Age*Diabetes
Age*Hypertension
Age*Smoking
Race/Ethnicity *Diabetes
Race/Ethnicity *Hypertension
Race/Ethnicity *Smoking
Sex*Diabetes
Sex*Hypertension
Sex*Smoking
3-level Age* Race/Ethnicity *Sex
Age* Race/Ethnicity *Diabetes
Age* Race/Ethnicity *Hypertension
Age* Race/Ethnicity *Smoking
Age*Sex*Diabetes
Age*Sex*Hypertension
Age*Sex*Smoking
Race/Ethnicity *Sex*Diabetes
Race/Ethnicity *Sex*Hypertension
Race/Ethnicity *Sex*Smoking
4-level Age* Race/Ethnicity *Sex*Diabetes
Age* Race/Ethnicity *Sex*Hypertension
Age* Race/Ethnicity *Sex*Smoking
Limitations

The NHIS data analyzed are limited in a few ways. NHIS does not publicly release state-level data, and therefore only national level data will be included in VEHSS. All responses are self-reported, or household reported in the case of children.  The self-report measures represent indicators that cannot be directly translated into the prevalence of clinically defined visual impairment or blindness. Finally, many of the new vision questions included in the 2016 and 2017 NHIS are not present in the 2018 and 2019 surveys nor in surveys within a similar time frame, making it difficult to compare across surveys or across years.

Please see the full VEHSS NHIS data analysis report for additional details on the analysis and validation of the VEHSS analysis of the NHIS.

Additional information about NHIS can be found on the CDC website.

[1] US Department of Health and Human Services. Centers for Disease Control and Prevention. National Center for Health Statistics. (2016). 2015 National health Interview Survey (NHIS) Public Use Data Release: Survey Description. Retrieved from: ftp://ftp.cdc.gov/pub/Health_Statistics/NCHS/Dataset_Documentation/NHIS/2015/srvydesc.pdf

[2] Parker JD, Talih M, Malec DJ, et al. (2017). National Center for Health Statistics Data Presentation Standards for Proportions. National Center for Health Statistics. Vital Health Stat 2(175).