Survey Measurement of Sex and Transgender Identity

in the Behavioral Risk Factor Surveillance System

Kathryn O’Neill

October 2023

FCSM
Herman, J. L., Flores, A. R., & O’Neill, K. K. (2022). How many adults and youth identify as transgender in the United States? The Williams 

Institute, UCLA School of Law. https://williamsinstitute.law.ucla.edu/publications/trans-adults-united-states/

1.3 million adults

300,000 youth
● BRFSS data have allowed for research into not only the size of the 

transgender population, but also its health (Du Bois et al., 2021; Alzahrani et al., 

2019; Downing & Przedworski, 2018; Du Bois et al., 2018; Meyer et al., 2017) and 

socioeconomic status (Carpenter et al., 2020) .

● The BRFSS remains the largest and most reliable source of populationbased sexual orientation and gender identity data since it began collecting 

such data in some states in 2014. 

● The survey consists of a rotating core of questions asked by all states, 

CDC-provided optional modules, and state-provided additions.
● The BRFSS sexual orientation and gender identity (SOGI) module has also 

attracted research into survey measures and methodology (Jesdale, 2021; 

Riley et al., 2017; Tordoff et al., 2019; Cicero et al., 2020; Lett & Everhart, 2022)

● A sex at birth (SAB) module was introduced in 2019, and has since been 

adopted by 11 states for at least one year in 2019-2021.
2019-2021
Research Questions

● How many people received different survey questions than they 

otherwise would have because of the sex at birth module? 

● How did transgender respondents respond? Were their answers about 

SAB consistent with the question about transgender identity?

● How does this affect missingness patterns for sex-specific health 

questions?
BRFSS measures

Screening section

Are you male or 

female?

● Male

● Female

Sex at Birth module

What was your sex at 

birth? Was it male or 

female? 

● Male

● Female

● Don’t know/not 

sure

● Refused

SOGI module: 

Transgender identity

Do you consider yourself to 

be transgender?

● Yes, Male to Female

● Yes, Female to Male

● Yes, Gender nonconforming

● No

● Don’t know/not sure

● Refused

If these contradict, the SAB module takes precedence 

in determining the sex-specific survey questions that 

are administered.
BRFSS measures

Screening section

Are you male or 

female?

● Male

● Female

Sex at Birth module

What was your sex at 

birth? Was it male or 

female? 

● Male

● Female

● Don’t know/not 

sure

● Refused

SOGI module: 

Transgender identity

Do you consider yourself to 

be transgender?

● Yes, Male to Female

● Yes, Female to Male

● Yes, Gender nonconforming

● No

● Don’t know/not sure

● Refused

California did not use this 

question; some state-years 

allowed ‘don’t know’ and 

‘refused’ responses Some states used their own version of a 

sex at birth module which differs from 

this, although this data is not included in 

national dataset. Such answers do affect 

classification of respondents and the 

health questions people receive
Screening section: Are you male or female?

Cell phone cellsex

State BRFSS 

administration

Landline

College housing

Multi-person household

One-person household

colgsex

landsex

respslct

sexvar
Screening section: Are you male or female?

Cell phone cellsex

State BRFSS 

administration

Landline

College housing

Multi-person household

One-person household

colgsex

landsex

respslct

sexvar

About 3% of respondents from 2019-2021, spread across states, have no 

values for any of these component variables, but do have a value for sexvar.
Screening section: Are you male or female?

Cell phone cellsex

State BRFSS 

administration

Landline

College housing

Multi-person household

One-person household

colgsex

landsex

respslct

sexvar

For some respondents, the values of the component variables do not 

match the value of sexvar. This is concentrated in some states.
BRFSS measures

Screening section

(sexvar)

Sex at Birth module

Survey classification of sex (_sex)
BRFSS measures

Screening section

(sexvar)

Sex at Birth module

Survey classification of sex (_sex)

Some states overrode the value of the screening section 

variable with the answer to the sex at birth question
BRFSS measures

Screening section

(sexvar)

Sex at Birth module

Survey classification of sex (_sex)

Some states overrode the value of the screening section 

variable with the answer to the sex at birth question

State-added SAB module
BRFSS measures

By relying on the final 

sex variable available in 

the dataset, we do not 

know what question(s) 

that value came from.

Additionally, 

respondents who 

answered different 

questions differently 

are hidden.

Screening section

(sexvar)

Sex at Birth module

Survey classification of sex (_sex)

Some states overrode the value of the screening section 

variable with the answer to the sex at birth question

State-added SAB module
BRFSS measures

Screening section

Are you male or 

female?

● Male

● Female

Sex at Birth module

What was your sex at 

birth? Was it male or 

female? 

● Male

● Female

● Don’t know/not 

sure

● Refused

SOGI module: 

Transgender identity

Do you consider yourself to 

be transgender?

● Yes, Male to Female

● Yes, Female to Male

● Yes, Gender nonconforming

● No

● Don’t know/not sure

● Refused

Rely on component variables 

only

Remove states known to have 

used their own SAB module
Research Questions

● How many people received different survey questions than they 

otherwise would have because of the sex at birth module? 

● How did transgender respondents respond? Were their answers about 

SAB consistent with the question about transgender identity?

● How does this affect missingness patterns for sex-specific health 

questions?
About 1% of all respondents answered these two questions differently
Among those that answered the two questions differently, only about 17% are 

transgender

80.3%

16.9%

2.8%

Not transgender Transgender Don't know or refused

Responses to “Are you male or female” and “What is 

your sex at birth” are different (n=1,514)
About 28% of transgender respondents answered these two questions differently
About half of transgender men and transgender women appear to have answered 

“Are you male or female” with their sex, and half with their implied gender

57.0%

50.2%

43.0%

49.8%

Transgender, "Male to Female” Transgender, "Female to Male”

Are you male or female?

Male

Female
18% to 21% of transgender respondents provide incongruent responses to the SAB 

question and the transgender identity question

79.0%

21.5% 18.1%

78.2%

0.9% 2.1% 0.3% 0.1%

Transgender, "Male to Female” Transgender, "Female to Male”

What was your sex at birth? Was it male or female?

Male Female Don’t Know/ not sure Refused
Sex-specific health questions

Pregnancy

Pap test

Hysterectomy

Mammogram

H.P.V test

Don’t know or refused: 0.6% - 9.9%

Prostate-specific antigen test 

(4 questions)

Don’t know or refused: 2.8%-5%
Sex-specific health questions
Results

● Survey classification of transgender respondents’ sex changes about 28% 

of the time in states which ask the sex at birth module.

● About 1% of all respondents’ sex was re-categorized by the SAB module. 

○ In states without the SAB module, this implies that 3,000 people per year were asked 

questions that were not relevant to them.

● Transgender respondents’ combinations of answers to questions about 

their transgender identity, sex at birth, and the screening question are 

quite diverse, implying a need for improvement in these measures.

● Some evidence that respondents classified as male are more likely to 

answer questions about prostate cancer screening in states which ask the 

sex at birth module. 
Implications - survey design

● As one of the largest health surveys in the world, measures of sex and/or 

gender should be clear, distinct, and measured well and consistently across 

states.

● State-added modules should not affect other items in the survey.

● Questions about sex should be asked consistently in form and method 

across states.

● Justify asking questions about sex at birth - i.e. , this information is needed 

for later health questions.

● Terminology could be more clear in the question of trangender identity; i.e., 

instead of “female to male”, "female sex assigned at birth, identify as a 

male".
Considerations when using BRFSS

● The sex at birth module is important, especially for transgender 

respondents, although only available in 11 states.

● Do not rely upon the recoded sex variables (sexvar and _sex) if the source 

of that variable is important (sex at birth module or screening question).

● Be aware that some states used their own SAB modules which are not 

included in the national dataset.

○ Be aware that some national documentation is misleading on this account. See CA sexvar 

2019.
Thank you!

Kathryn O’Neill

onk@sas.upenn.edu

Sociology & Demography

University of Pennsylvania

she/her
New York 2021
Maine 2020
California 2019

Screening section
About 0.6% of the sample is transgender.

Among those that answered the two questions differently, only about 17% are 

transgender
About half of transgender men and transgender women appear to have answered 

“Are you male or female” with their sex, and half with their implied gender
18% to 21% of transgender respondents provide incongruent responses to the SAB 

question and the transgender identity question

https://translegislation.com/learn