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. Author manuscript; available in PMC: 2016 Jan 31.
Published in final edited form as: Soc Sci Med. 2014 Jul 30;127:181–189. doi: 10.1016/j.socscimed.2014.07.065

Table 2.

Cross-Section and Within-MZ Twin Pairs Association between Grades of Schooling and Health

Cross-Section Cross-Section with
measurement error		 Within-MZ Twins Within-MZ Twins for
twin pairs where one
has ≥16 & other
has ≤14 grades		 Within-MZ Twins with
measurement error
β 95% CI β 95% CI β 95% CI β 95% CI β 95% CI
MATR-MTR
Self-reported health 0.07 0.06 to 0.08 0.08 0.06 to 0.08 0.04 0.01 to 0.06 0.04 0.01 to 0.07 0.05 −0.01 to 0.10
N 5638 5638 2819 367 2819
BMI −0.23 −0.27 to −0.17 −0.28 −0.34 to −0.21 −0.02 −0.11 to 0.07 0.03 −0.11 to 0.17 −0.03 −0.22 to 0.16
N 5562 5562 2781 364 2781
Overweight −0.02 −0.03 to −0.02 −0.03 −0.04 to −0.02 −0.00 −0.01 to 0.01 −0.00 −0.01 to 0.01 −0.01 −0.04 to 0.02
N 5562 5562 2781 364 2781
MATR
Never Smoked 0.02 0.01 to 0.02 0.02 0.01 to 0.03 0.00 −0.01 to 0.02 0.00 −0.02 to 0.02 0.01 −0.04 to 0.06
N 4126 4126 2063 256 2063
Alcohol Consumption 0.09 −0.02 to 0.18 0.12 0.01 to 0.22 −0.06 −0.29 to 0.17 0.17 −0.22 to 0.57 −0.35 −1.25 to 0.56
N 3392 3392 1696 207 1696
Exercise 0.04 0.03 to 0.05 0.04 0.03 to 0.05 0.01 −0.01 to 0.03 0.02 −0.01 to 0.05 0.08 0.01 to 0.14
N 4240 4240 2120 258 2120
NAS-NRC
Self-reported health 0.07 0.05 to 0.08 0.03 −0.00 to 0.07 0.02 −0.02 to 0.08
N 1868 934 116
BMI −0.12 −0.16 to 0.07 −0.06 −0.15 to −0.04 −0.05 −0.18 to 0.08
N 1844 922 114
Overweight −0.01 −0.21 to −0.01 −0.00 −0.02 to 0.01 −0.00 −0.02 to 0.22
N 1844 922 114
Limiting Activities −0.26 −0.33 to −0.18 −0.03 −0.19 to 0.13 0.06 −0.16 to 0.28
N 1726 863 107
No. of health problems −0.01 −0.03 to 0.02 −0.03 −0.08 to 0.06 −0.02 −0.09 to 0.05
N 1342 671 81
Never Smoked 0.03 0.02 to 0.04 0.01 −0.01 to 0.02 0.01 −0.01 to 0.03
N 1902 951 117

Notes: Cross sectional regressions in MATR-MTR control for age, age squared, gender, early health problems and an indicator for MATR. Cross-sectional regressions for MATR control for age, age squared, gender and early health problems. Cross-sectional regressions in NAS-NRC control for age and age squared. For the cross-section corrected for measurement error, twin 1’s schooling is instrumented by twin 2’s report of twin 1’s schooling and vice versa. Within-MZ twins estimates for MATR-MTR and MATR control for early health problems. For within-MZ twins estimates corrected for measurement error, the difference in self-reported schooling is instrumented by the difference in the co-twin’s report of the other’s schooling. 95% confidence intervals based on standard errors clustered by twin pairs.