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Danan Gu

service providers to offer people-centered programs, and benefit clinical programs that are
oriented to enhance the health of older adults.
2. Methods

2.1 Study Sample

The data came from five waves of the Chinese Longitudinal Healthy Longevity Survey
(CLHLS) in 2000, 2002, 2005, 2008, and 2011. Started in 1998, the CLHLS is a national
survey focusing on the oldest-old to investigate the determinants of health and longevity.
The CLHLS is supported by an ongoing National Institute on Aging grant awarded to
Duke University (USA) and Peking University (China). To avoid probable age exaggera-
tion among ethnic minorities, the CLHLS only covered 22 Han-ethnicity dominated prov-
inces in mainland China, which accounted for more than 80% of the population in the lat-
est census.
The CLHLS aims to interview all centenarians in a randomly selected half of the coun-
ties/cities in 22 provinces. Age of each centenarian was validated from various sources as
available, including birth certificates, genealogical documents, household booklets, and
ages of their children and siblings (Zeng and Gu, 2008). For each centenarian interviewed,
one nearby respondent from each of three age groups (ages 65–79, ages 80–89, and ages
90–99) with predesignated age and sex was randomly chosen to be interviewed based on a
random code assigned to the centenarian. All information was obtained through in-home
interviews and informed consent was obtained from each respondent. The accuracy of age
reporting of centenarians and the data quality of other variables in the CLHLS are quite
good (Gu, 2008; Gu and Dupre, 2008; Zeng and Gu, 2008). Detailed sampling procedures
can be found elsewhere (Gu, 2008; Zeng and Gu, 2008).
The first wave (1998) of the CLHLS was not used in this study because the wording of
the responses to questions related to distress in the 1998 wave was not the same as those in
other waves. Furthermore, those who were lost to follow-up at a subsequent wave were
dropped in the analysis because our focus is on mortality risk and because we do not know
their survival status. This exclusion resulted in a final sample size of 30,948 respondents
aged 65 and older with 49,218 observations. Figure 1 illustrates the sample distribution
across waves.

2.2 Measurements
2.2.1 Measures of Objective Successful Aging
Objective successful aging (OSA) was defined by absence of any chronic disease, no
functional disability, and no cognitive impairment. By contrast, a respondent was consi-
dered as not-OSA if he or she reported any of these three conditions. The CLHLS adopted
a list of twenty diseases to measure comorbidity. An individual was coded as having no
chronic conditions if he or she did not self-report any of the twenty disease conditions (e.g.,
heart diseases, stroke, diabetes, hypertension, cancers, cataracts, Parkinson's disease) at the
time of the surveys. As 95% of these self-reported diseases were confirmed by physicians,
chronic disease conditions are assumed to be reliable, although underreporting is still
possible (Gu, 2014). Activities of daily living (ADL) were used as a proxy measure of
physical function. A respondent was considered as ADL disabled if he or she needed as-
sistance in performing any of six tasks (bathing, dressing, indoor transferring, toileting,
eating, and continence) at the time of the surveys. Cognitive impairment was measured by
the Chinese version of the Mini-mental Status Examination (MMSE), which includes six
domains of cognition (orientation, reaction, calculation, short memory, naming, and lan-
guage) with a total score of 30. The Chinese version of the MMSE was adapted from the

International Journal of Population Studies | 2015, Volume 1, Issue 1 31