NLSY79 Appendix 19: SF-12 Health Scale Scoring

The SF-12, which stands for short-form 12-question, is a brief inventory of self-reported mental and physical health. This scale was administered to respondents who had turned 40 since their last interview as part of the age 40+ health module, included in the 1998, 2000, 2002, 2004, and 2006 surveys, and in the 50+ health module administered in the 2008, 2010, 2012 and 2014 surveys.

Rather than using the twelve questions separately, SF-12 users often create two summary scores:

• PCS-12 or Physical Component Summary (measures physical health): question name H40-SF12_PCS_SCORE, H50-SF12_PCS_SCORE
• MCS-12 or Mental Component Summary (measures mental health): question name H40-SF12_MCS_SCORE, H50-SF12_MCS_SCORE

CHRR has received permission to calculate these summary scores for NLSY79 respondents and release the scores with the main data set. Scores are created according to the manual by Ware, Kosinski, and Keller (1995) and are provided on the data set with the question names listed above. However, we are not permitted to release the scoring formula; interested users can purchase the scoring manual from Optum (https://www.optum.com/optum-outcomes.html), which now owns the SF surveys.  For users looking at the SF surveys on the Internet (https://www.optum.com/optum-outcomes/what-we-do/health-surveys/sf-12v2-health-survey.html), note that the NLSY79 uses version 1, not version 2 of the survey.

In large national surveys of the entire US population, both the PCS-12 and MCS-12 have a mean of 50 and a standard deviation of 10. The interpretation of these two scores is straightforward. NLSY79 respondents with a score above 50 have better health than the typical person in the general U.S. population (age is not held constant). NLSY79 respondents with scores below 50 have worse health than the typical U.S. person. Each one-point difference above or below 50 corresponds to a one-tenth of a standard deviation. For example, a person with a score of 30 is two standard deviations away from the mean.

Table 1. Summary Statistics for NLSY79 SF-12 Scores

As Table 1 indicates, the typical NLSY79 respondent self-reports better health than the typical U.S. respondent while in their 40s. This matches the results described in the SF-12 scoring manual, which in addition to population norms reports the norms for U.S. residents who are between the ages of 35 and 44. The manual reports the mean PCS score for this subgroup as 52.18 (std. dev. 7.30) and the mean MCS score as 50.1 (std. dev. 8.62).

The SF-12 scoring manual also indicates that for U.S. residents between the ages of 45 and 54, the mean PCS score is 49.71 (std. dev. 9.5) and the mean MCS score is 50.45 (std. dev. 9.55). NLS respondents in 2008, have higher MCS scores than the overall population and similar PCS scores.

Overall, the SF-12 manual shows higher-than-average physical scores prior to age 55 and rapidly falling scores after that age. Mental scores do not appear to decline with age. Information from the NLSY79 40+ and 50+ health modules appear to match this pattern.

Reference

Ware, John, Mark Kosinski and Susan Keller. 1995. SF-12: How to Score the SF-12 Physical and Mental Health Summary Scales, 2nd edition. Boston: The Health Institute, New England Medical Center.