Ongoing assessment of the health status of the
population is a core function of local health
departments, and improving the availability of high
quality health information remains a major priority for
the Los Angeles County Department of Public Health (DPH).
The Office of Health Assessment and Epidemiology (OHAE)
within DPH is charged with carrying out this assessment
function by collecting and disseminating
population-based health information to plan, evaluate,
and develop policy, and to serve local communities and
agencies engaged in improving the health status of LA
County residents.
The Los Angeles County Health Survey (LACHS) functions
as a primary vehicle for gathering information about
access to health care, health care utilization, health
behaviors, health status, and knowledge and perceptions
of health-related issues among the LA County population.
The 2007 LACHS is the fifth in a series, following
surveys conducted in 1997, 1999, 2002 and 2005. Each
LACHS has included an adult component and a child
component, administered to the parent or guardian
(usually the mother) of a child 0-17 years old. Recent
surveys have also included 7 or 8 subsample sections,
each administered to a portion of the adult survey
population.
The purpose of the health survey is to provide updates on key health indicators and to identify emerging public health issues among adults and children residing in the County's eight service planning areas (SPAs) and 26 health districts. Importantly, the survey allows the Department of Public Health to track health issues over time. To properly address the root causes of poor health, the survey looks beyond risk factors for individual diseases to factors in the physical and social environment that influence health, such as land use, safety, poverty, and educational attainment.
The large sample size of each LACHS enables the survey to provide estimates not only of the health of the county population overall, but of people residing in the County’s many different geographic regions. The survey also provides valuable information about the health of the county’s major racial/ethnic sub-groups and numerous other demographic groups. Data are collected from households of all educational and income levels, including the most vulnerable residents living below the federal poverty level.
The 2007 Los Angeles County Health Survey (LACHS) was
commissioned by the Los Angeles County Department of
Public Health and was conducted by the Field Research
Corporation. Data collection occurred from April 2007 to
January 2008. Funding for the survey was provided by
grants from First 5 LA and the Department of Public
Health Tobacco Control and Prevention Program, Emergency
Preparedness and Response Program, Alcohol and Drug
Program Administration, Office of AIDS Programs and
Policies, and the Maternal, Child, and Adolescent Health
program.
Sample Size: A total of
7,200 adults (ages 18 years or older) residing in Los
Angeles County were interviewed for the Adult survey. In
addition, 5,728 interviews were conducted among the
parents (primarily mothers) of children ages 17 years or
under. Respondents in each household were randomly
selected using an unrestricted random digit dial
sampling methodology, which included all eligible LA
County households with landline telephones.
Languages: Interviews
were conducted in English, Spanish, Chinese (Mandarin
and Cantonese), Korean and Vietnamese. Over one quarter
(26%) of all interviews in the 2007 LACHS Adult Survey
were completed in non-English languages, while over four
in ten parents (43%) were interviewed in a non-English
language as part of the Child Survey.
Weighting: Statistical
weighting is utilized to generalize the sample survey
data to the overall LA County population. For adult,
child, and subsample data files, appropriate weights
were developed to account for differences in the
probability of selection of households into each sample
and to align the survey results to known geographic and
demographic characteristics of the County’s adult and
child populations. This process involved calculating a
household weight and a population rate for each
individual record, and projecting the data files to the
population of residential housing units and the
population of non-institutionalized adults and children
in Los Angeles County.
Cooperation Rate: The
overall cooperation rates for adult and child surveys
were 40% each, meaning that 40% of the people who
answered the phone were willing to complete the
interview with the surveyor. Notably, the 2007 LACHS
incorporated a pre-approach letter, which notified
households whose phone numbers were randomly generated
for the survey that they would receive a call from the
County Department of Public Health. The cooperation rate
of households mailed the pre-approach letter was nine
percentage points higher (47%) than those that were not
mailed the letter or whose letter was returned as
undeliverable (38%).
Response Rate: The
response rate is the number of completed survey
interviews divided by the total number of phone numbers
selected for the survey sample, including
non-residential numbers, numbers where contact with a
household member was never achieved, and numbers where
the person who answered the phone did not wish to begin
or complete the survey. The 2007 LACHS response rate was
18% for the Adult Survey and 15% for the Child Survey
(including homes ineligible because no children resided
there.) The response rates achieved in the 2007 LACHS
were lower than those achieved in earlier LACHS studies
in 2002 (31.1% Adult, 33.9% Child), and 2005 (22.8%
Adult, 26% Child).
Declining response rates are not just a problem for the LACHS, but for all telephone surveys conducted by the leading survey research organizations in the U.S. in recent years. In Los Angeles County, telephone surveys are particularly difficult to execute. While we understand that lower response rates are not ideal, we believe that the survey procedures employed in the implementation of the 2007 LACHS have yielded accurate and reliable data for both the Adult Survey and the Child Survey.
For more detailed information about the 2007 Los
Angeles County Health Survey methods, please see our
full methodology document.
Topics of 2007 Health Survey
