Table 4.
Hazard Ratios for Mortality Risk Associated with Higher Levels of Subjective Wellbeing (SWB): Individual-Level and Within-Pair Difference Effects of Life Satisfaction and Affect
| Individual-level analyses | Within-pair analyses | |||||
|---|---|---|---|---|---|---|
|
| ||||||
| All twins | DZ twins | MZ twins | ||||
| HR (95% CI) | p-value | HR (95% CI) | p-value | HR (95% CI) | p-value | |
|
| ||||||
| Affect | N=6,802 | N=2,283 | N=2,102 | |||
| Affect | 0.77 (0.74, 0.80) | <0.0001 | 0.76 (0.69, 0.83) | <0.0001 | 0.77 (0.68, 0.87) | <0.0001 |
| Age at intake | 0.89 (0.89, 0.90) | <0.0001 | 0.91 (0.89, 0.93) | <0.0001 | 0.91 (0.90, 0.93) | <0.0001 |
| Sex (female) | 0.56 (0.51, 0.61) | <0.0001 | 0.64 (0.55, 0.74) | <0.0001 | 0.68 (0.56, 0.82) | <0.0001 |
| Cohort (MADT) | 0.68 (0.57, 0.82) | <0.0001 | 0.72 (0.54, 0.98) | 0.034 | 0.98 (0.70, 1.39) | 0.927 |
| Affect adjusted | N=6,674 | N=2,253 | N=2,066 | |||
| Affect | 0.85 (0.81, 0.88) | <0.0001 | 0.82 (0.75, 0.90) | <0.0001 | 0.82 (0.72, 0.92) | 0.001 |
| Age at intake | 0.88 (0.87, 0.89) | <0.0001 | 0.90 (0.88, 0.91) | <0.0001 | 0.90 (0.89, 0.92) | <0.0001 |
| Sex (female) | 0.53 (0.49, 0.58) | <0.0001 | 0.61 (0.52, 0.71) | <0.0001 | 0.65 (0.54, 0.79) | <0.0001 |
| Cohort (MADT) | 0.60 (0.50, 0.72) | <0.0001 | 0.65 (0.48, 0.89) | 0.008 | 0.88 (0.61, 1.26) | 0.484 |
| Number of medications | 1.13 (1.11, 1.15) | <0.0001 | 1.13 (1.10, 1.16) | <0.0001 | 1.11 (1.07, 1.16) | <0.0001 |
| Cognitive score | 0.82 (0.79, 0.85) | <0.0001 | 0.82 (0.76, 0.88) | <0.0001 | 0.80 (0.73, 0.89) | <0.0001 |
| Affect fully adjusted | N=6,669 | N=2,233 | N=2,065 | |||
| Affect | 0.90 (0.87, 0.94) | <0.0001 | 0.88 (0.79, 0.96) | 0.007 | 0.85 (0.75, 0.96) | 0.011 |
| Age at intake | 0.86 (0.86, 0.87) | <0.0001 | 0.88 (0.87, 0.90) | <0.0001 | 0.89 (0.87, 0.91) | <0.0001 |
| Sex (female) | 0.51 (0.47, 0.56) | <0.0001 | 0.59 (0.51, 0.69) | <0.0001 | 0.63 (0.53, 0.76) | <0.0001 |
| Cohort (MADT) | 0.44 (0.37, 0.54) | <0.0001 | 0.48 (0.35, 0.66) | <0.0001 | 0.70 (0.48, 1.00) | 0.050 |
| Number of medications | 1.09 (1.07, 1.11) | <0.0001 | 1.09 (1.06, 1.12) | <0.0001 | 1.07 (1.03, 1.11) | <0.001 |
| Cognitive score | 0.88 (0.84, 0.91) | <0.0001 | 0.87 (0.81, 0.94) | <0.001 | 0.84 (0.76, 0.93) | 0.001 |
| Physical health rating | 0.73 (0.70, 0.77) | <0.0001 | 0.73 (0.68, 0.79) | <0.0001 | 0.72 (0.65, 0.79) | <0.0001 |
| Life satisfaction | N=6,800 | N=2,282 | N=2,101 | |||
| Life satisfaction | 0.75 (0.72, 0.78) | <0.0001 | 0.75 (0.68, 0.82) | <0.0001 | 0.78 (0.70, 0.87) | <0.0001 |
| Age at intake | 0.89 (0.89, 0.90) | <0.0001 | 0.91 (0.89, 0.93) | <0.0001 | 0.92 (0.90, 0.94) | <0.0001 |
| Sex (female) | 0.57 (0.53, 0.63) | <0.0001 | 0.65 (0.56, 0.76) | <0.0001 | 0.68 (0.57, 0.82) | <0.0001 |
| Cohort (MADT) | 0.71 (0.60, 0.85) | <0.001 | 0.73 (0.54, 0.98) | 0.035 | 1.07 (0.76, 1.51) | 0.708 |
| Life satisfaction adjusted | N=6,673 | N=2,235 | N=2,065 | |||
| Life satisfaction | 0.82 (0.78, 0.85) | <0.0001 | 0.79 (0.72, 0.87) | <0.0001 | 0.83 (0.74, 0.92) | 0.001 |
| Age at intake | 0.88 (0.87, 0.89) | <0.0001 | 0.90 (0.88, 0.91) | <0.0001 | 0.91 (0.89, 0.93) | <0.0001 |
| Sex (female) | 0.54 (0.49, 0.59) | <0.0001 | 0.61 (0.52, 0.71) | <0.0001 | 0.65 (0.54, 0.79) | <0.0001 |
| Cohort (MADT) | 0.61 (0.51, 0.73) | <0.0001 | 0.65 (0.47, 0.89) | 0.006 | 0.92 (0.64, 1.32) | 0.653 |
| Number of medications | 1.13 (1.11, 1.15) | <0.0001 | 1.13 (1.10, 1.16) | <0.0001 | 1.12 (1.08, 1.16) | <0.0001 |
| Cognitive score | 0.82 (0.79, 0.85) | <0.0001 | 0.82 (0.76, 0.88) | <0.0001 | 0.80 (0.72, 0.88) | <0.0001 |
| Life satisfaction fully adjusted | N=6,668 | N=2,233 | N=2,064 | |||
| Life satisfaction | 0.88 (0.84, 0.92) | <0.0001 | 0.84 (0.76, 0.93) | <0.001 | 0.88 (0.79, 0.99) | 0.026 |
| Age at intake | 0.86 (0.86, 0.87) | <0.0001 | 0.88 (0.87, 0.90) | <0.0001 | 0.89 (0.88, 0.91) | <0.0001 |
| Sex (female) | 0.51 (0.47, 0.56) | <0.0001 | 0.59 (0.51, 0.69) | <0.0001 | 0.64 (0.53, 0.77) | <0.0001 |
| Cohort (MADT) | 0.46 (0.38, 0.55) | <0.0001 | 0.48 (0.35, 0.67) | <0.0001 | 0.71 (0.49, 1.03) | 0.068 |
| Number of medications | 1.09 (1.07, 1.11) | <0.0001 | 1.09 (1.06, 1.12) | <0.0001 | 1.07 (1.03, 1.11) | <0.001 |
| Cognitive score | 0.87 (0.84, 0.91) | <0.0001 | 0.87 (0.81, 0.94) | <0.001 | 0.84 (0.76, 0.92) | <0.001 |
| Physical health rating | 0.74 (0.71, 0.78) | <0.0001 | 0.74 (0.69, 0.81) | <0.0001 | 0.72 (0.65, 0.80) | <0.0001 |
Hazard ratios (95% confidence intervals) and p-values for both measures of SWB in the combined sample. Unadjusted models include age at intake and sex as covariates, adjusted models include age at intake, sex, number of medications, and cognitive scores as covariates, fully adjusted models additionally include physical health functioning. Sample sizes for within-pair analyses are not necessarily even because, while only complete pairs are used in estimating the effect of SWB, incomplete pairs add information to the effects of the covariates. The within-pair analyses using gamma between-within models are able to estimate the effects of the covariates like sex and age even though these are shared within a twin pair. These estimates are the effect of the covariate holding the twin pair mean and individual score on SWB constant, similar to the individual-level effect of these covariates.