Table 3.
Natural Direct and Indirect Effects of Physical Activitya on Incidence of Mortality, Dementia/Cognitive Impairment Without Dementia, and Depressive Symptoms as Estimated by Levels of Inflammatory Biomarkers (Mediation Analysis Results From an Additive Hazards Model), Sacramento Area Latino Study on Aging, 1998–2007b
| Potential Mediator | Mortality | Dementia/CIND | Depressive Symptoms | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of Incident Casesc | 95% CI | Proportion Mediated, % | 95% CI | No. of Incident Casesc | 95% CI | Proportion Mediated, % | 95% CI | No. of Incident Casesc | 95% CI | Proportion Mediated, % | 95% CI | |
| C-reactive protein | ||||||||||||
| NDE | 1,553 | 786, 2,319 | 573 | 31, 1,115 | 1,694 | −179, 3,567 | ||||||
| NIE | 2 | −53, 56 | 0 | −4, 4 | −23 | −56, 9 | N/Ad | 6 | −93, 105 | 0 | −14, 16 | |
| Interleukin 6 | ||||||||||||
| NDE | 1,405 | 648, 2,162 | 512 | −34, 1,058 | 1,708 | −211, 3,627 | ||||||
| NIE | 122 | 51, 194 | 8 | 3, 18 | 49 | 5, 94 | 9 | −2, 57 | 51 | −104, 205 | 3 | −16, 30 |
| Interleukin 6 receptor | ||||||||||||
| NDE | 1,552 | 747, 2,356 | 565 | 24, 1,106 | 1,833 | −88, 3,755 | ||||||
| NIE | 11 | −15, 36 | 1 | −1, 3 | −2 | −14, 9 | 0 | −5, 3 | −35 | −88, 19 | N/A | |
| TNF-α | ||||||||||||
| NDE | 1,412 | 611, 2,213 | 379 | −170, 929 | 1,987 | 40, 3,935 | ||||||
| NIE | 126 | 61, 191 | 8 | 4, 18 | 9 | −32, 49 | 2 | −37, 48 | −43 | −210, 124 | N/A | |
| TNF-α receptor 1 | ||||||||||||
| NDE | 1,401 | 623, 2,179 | 353 | −192, 899 | 1,760 | −113, 3,632 | ||||||
| NIE | 147 | 62, 231 | 9 | 4, 20 | 50 | −4, 104 | 12 | −80, 116 | 40 | −78, 158 | 2 | −11, 22 |
| TNF-α receptor 2 | ||||||||||||
| NDE | 1,356 | 573, 2,139 | 315 | −219, 849 | 1,805 | −116, 3,725 | ||||||
| NIE | 154 | 69, 240 | 10 | 5, 23 | 40 | −13, 93 | 11 | −95, 129 | 53 | −117, 223 | 3 | −17, 29 |
Abbreviations: CI, confidence interval; CIND, cognitive impairment without dementia; MET, metabolic equivalent of task; N/A, not applicable; NDE, direct effect; NIE, indirect effect; TNF-α, tumor necrosis factor α.
a Physical activity exposure was defined as low (<35 MET-hours/week) versus high (≥35 MET-hours/week).
b Baseline inflammation exposure was defined as less than the third quartile versus greater than or equal to the third quartile. The proportion mediated was defined as the ratio of the indirect effect to the total effect for a low versus high physical activity level. The model adjusted for age, sex, education, smoking, body mass index, and Charlson comorbidity index.
c Additional incident cases per 100,000 person-years at risk.
d N/A because of negative estimates.