Table 2.
Distribution and Relative Risk of Late-Life Depression among 21,728 Elderly Women in the Nurses’ Health Study, 2000–2010
| Variable | No. of cases/person-years | Incident rate per 1000 person-years | Model 1a
|
Model 2b
|
Model 3c
|
||||
|---|---|---|---|---|---|---|---|---|---|
| HR | 95% CI | HR | 95% CI | HR | (95% CI) | P for trend | |||
| Education level | |||||||||
| Registered nurse degree | 2973/129700 | 22.92 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | 0.26 |
| Bachelor degree | 687/34277 | 20.04 | 0.92 | 0.85, 1.00 | 0.98 | 0.90, 1.07 | 0.99 | 0.91, 1.08 | |
| Advanced degree | 285/16163 | 17.63 | 0.81 | 0.71, 0.91 | 0.92 | 0.82, 1.03 | 0.92 | 0.81, 1.04 | |
| Race/ethnicity | |||||||||
| Non-Hispanic White | 3841/175121 | 21.93 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | N/A |
| Black | 33/1673 | 19.72 | 0.88 | 0.63, 1.24 | 0.88 | 0.63, 1.25 | 0.88 | 0.62, 1.25 | |
| Others | 71/3346 | 21.22 | 1.02 | 0.81, 1.29 | 1.13 | 0.89, 1.43 | 1.11 | 0.88, 1.40 | |
| Social network (quintiles) | |||||||||
| 5th quintile (most social integration) | 480/24739 | 19.40 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | 0.99 |
| 4th quintile | 1249/59475 | 21.00 | 1.06 | 0.95, 1.18 | 1.02 | 0.92, 1.14 | 1.03 | 0.92, 1.14 | |
| 3rd quintile | 762/32244 | 23.63 | 1.20 | 1.07, 1.35 | 1.16 | 1.03, 1.30 | 1.14 | 1.01, 1.28 | |
| 2nd quintile | 574/24833 | 23.11 | 1.17 | 1.04, 1.32 | 1.07 | 0.95, 1.21 | 1.09 | 0.96, 1.23 | |
| 1st quintile (least social integration) | 880/38850 | 22.65 | 1.15 | 1.03, 1.29 | 1.05 | 0.94, 1.18 | 1.05 | 0.94, 1.18 | |
| Subjective social status | |||||||||
| High | 458/25590 | 17.90 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | 0.002 |
| Medium-high | 2042/97251 | 21.00 | 1.17 | 1.06, 1.30 | 1.10 | 1.00, 1.22 | 1.09 | 0.98, 1.21 | |
| Medium-low | 1338/54431 | 24.58 | 1.32 | 1.19, 1.47 | 1.16 | 1.04, 1.30 | 1.14 | 1.02, 1.27 | |
| Low | 107/2869 | 37.29 | 1.93 | 1.56, 2.38 | 1.50 | 1.21, 1.85 | 1.45 | 1.17, 1.80 | |
| Regular caregiving to children/grandchildren | |||||||||
| No | 2820/125249 | 22.52 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | 0.02 |
| Some (1–20 hrs/wk) | 9451/46027 | 20.53 | 0.97 | 0.90, 1.04 | 0.94 | 0.87, 1.01 | 0.94 | 0.87, 1.01 | |
| A lot (>20 hrs/wk) | 180/8865 | 20.30 | 0.95 | 0.82, 1.11 | 0.87 | 0.75, 1.02 | 0.87 | 0.74, 1.01 | |
| Regular caregiving to disabled or ill relatives | |||||||||
| No | 2981/141438 | 21.08 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | <0.0001 |
| Some (1–40 hrs/wk) | 724/30837 | 23.48 | 1.13 | 1.04, 1.23 | 1.15 | 1.06, 1.25 | 1.15 | 1.06, 1.25 | |
| A lot (>40 hrs/wk) | 240/7866 | 30.51 | 1.40 | 1.23, 1.60 | 1.34 | 1.18, 1.54 | 1.33 | 1.17, 1.52 | |
| Body mass index (BMI) | |||||||||
| <18.5 | 118/4798 | 24.59 | 1.19 | 0.99, 1.44 | 1.13 | 0.90, 1.41 | 1.13 | 0.94, 1.36 | 0.006 |
| 18.5–24.9 | 1752/84579 | 20.71 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |
| 25.0–29.9 | 1342/59976 | 22.38 | 1.08 | 1.01, 1.16 | 1.02 | 0.95, 1.09 | 0.97 | 0.90, 1.04 | |
| 30.0–34.9 | 531/22618 | 23.48 | 1.16 | 1.05, 1.27 | 0.96 | 0.87, 1.06 | 0.92 | 0.83, 1.01 | |
| ≥35.0 | 202/8170 | 24.73 | 1.23 | 1.06, 1.42 | 0.95 | 0.83, 1.10 | 0.86 | 0.73, 1.00 | |
| Alternate Mediterranean diet score (quintiles)d | |||||||||
| 5th quintile (most adherence) | 659/34621 | 19.03 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | 0.12 |
| 4th quintile | 889/44447 | 20.00 | 1.14 | 1.03, 1.26 | 1.04 | 0.93, 1.15 | 1.04 | 0.95, 1.15 | |
| 3rd quintile | 751/33701 | 22.28 | 1.19 | 1.07, 1.32 | 1.03 | 0.92, 1.16 | 1.03 | 0.93, 1.15 | |
| 2nd quintile | 819/34454 | 23.77 | 1.28 | 1.15, 1.43 | 1.03 | 0.91, 1.16 | 1.08 | 0.96, 1.28 | |
| 1st quintile (least adherence) | 827/32917 | 25.10 | 1.36 | 1.21, 1.51 | 1.04 | 0.91, 1.18 | 1.09 | 0.98, 1.22 | |
| Cigarette smoking | |||||||||
| Never smoker | 1695/85031 | 19.93 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | <0.0001 |
| Past smoker | 2015/86449 | 23.31 | 1.21 | 1.13, 1.29 | 1.15 | 1.07, 1.23 | 1.16 | 1.08, 1.24 | |
| Current smoker, 1–14 cig/d | 114/5018 | 22.72 | 1.16 | 0.96, 1.41 | 1.31 | 1.10, 1.55 | 1.11 | 0.91, 1.34 | |
| Current smoker,15–24 cig/d | 97/2966 | 32.71 | 1.68 | 1.37, 2.06 | 1.53 | 1.26, 1.86 | 1.44 | 1.17, 1.78 | |
| Current smoker, ≥25 cig/d | 24/676 | 32.71 | 1.81 | 1.20, 2.71 | 1.81 | 1.28, 2.55 | 1.54 | 1.02, 2.32 | |
| Moderate to vigorous activity | |||||||||
| ≥5.0 hours/week (hrs/wk) | 334/24206 | 13.80 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | <0.0001 |
| 2.5–4.99 hrs/wk | 435/24678 | 17.63 | 1.11 | 0.96, 1.28 | 1.12 | 0.98, 1.28 | 1.03 | 0.89, 1.19 | |
| 1.0–2.49 hrs/wk | 475/23689 | 20.05 | 1.23 | 1.07, 1.42 | 1.18 | 1.03, 1.35 | 1.08 | 0.93, 1.24 | |
| 0.1–0.99 hrs/wk | 780/29928 | 26.06 | 1.47 | 1.29, 1.67 | 1.23 | 1.09, 1.40 | 1.20 | 1.05, 1.37 | |
| 0 hr/wk | 1921/77639 | 24.74 | 1.60 | 1.42, 1.80 | 1.19 | 1.06, 1.33 | 1.23 | 1.09, 1.39 | |
| Largest number of drinks in a single day | |||||||||
| none | 1695/73540 | 23.05 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | 0.07 |
| 1–2 drinks | 1838/88951 | 20.66 | 0.93 | 0.87, 1.00 | 1.00 | 0.94, 1.08 | 1.00 | 0.94, 1.08 | |
| ≥3 drinks | 412/17650 | 23.34 | 1.13 | 1.01, 1.26 | 1.16 | 1.03, 1.30 | 1.15 | 1.03, 1.29 | |
| Comorbidity | |||||||||
| ≤1 | 3248/159538 | 20.36 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | N/A |
| ≥2 | 697/20603 | 33.83 | 1.64 | 1.51, 1.78 | 1.29 | 1.16, 1.43 | 1.40 | 1.28, 1.52 | |
| Hours of actual sleep per day | |||||||||
| ≤6 hrs | 1101/44445 | 24.77 | 1.23 | 1.15, 1.32 | 0.98 | 0.91, 1.06 | 1.03 | 0.95, 1.11 | 0.0006 |
| 7–8 hrs | 2442/121415 | 20.11 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | |
| 9 hrs | 322/12470 | 25.82 | 1.28 | 1.14, 1.44 | 1.18 | 1.04, 1.34 | 1.21 | 1.08, 1.36 | |
| ≥10 hrs | 80/1810 | 44.19 | 2.26 | 1.80, 2.82 | 1.51 | 1.18, 1.93 | 1.96 | 1.56, 2.46 | |
| Difficulty falling asleep or staying asleep | |||||||||
| None of the time | 1034/63460 | 16.29 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | <0.0001 |
| A little of the time | 1221/59950 | 20.37 | 1.25 | 1.15, 1.36 | 1.21 | 1.11, 1.31 | 1.21 | 1.11, 1.31 | |
| Some of the time | 1437/50739 | 28.32 | 1.73 | 1.59, 1.87 | 1.55 | 1.43, 1.69 | 1.53 | 1.41, 1.67 | |
| Most or all of the time | 253/5991 | 42.23 | 2.52 | 2.19, 2.89 | 2.10 | 1.81, 2.44 | 2.04 | 1.77, 2.36 | |
| Bodily pain | |||||||||
| None | 467/34210 | 13.65 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | <0.0001 |
| Very mild/mild | 2125/105754 | 20.09 | 1.48 | 1.34, 1.64 | 1.29 | 1.17, 1.43 | 1.29 | 1.17, 1.43 | |
| Moderate | 1129/35440 | 31.86 | 2.24 | 2.01, 2.49 | 1.67 | 1.48, 1.87 | 1.65 | 1.47, 1.85 | |
| Severe/very severe | 224/4737 | 47.29 | 3.21 | 2.74, 3.77 | 2.23 | 1.89, 2.63 | 2.22 | 1.88, 2.62 | |
| Physical/functional limitation | |||||||||
| No | 793/55594 | 14.26 | 1.00 | Referent | 1.00 | Referent | 1.00 | Referent | N/A |
| Yes | 3152/124547 | 25.31 | 1.86 | 1.72, 2.02 | 1.37 | 1.26, 1.48 | 1.42 | 1.30, 1.55 | |
Abbreviations: HR, hazard ratio; CI, confidence interval; N/A, not applicable; hrs/wk, hours per week
a
Model 1 adjusted for age (years) only (predictors are time-varying when applicable).
b
Model 2 simultaneously adjusted for age (years) and baseline covariates listed in the table.
c
Model 3 simultaneously adjusted for age (years) and time-varying covariates (except for subjective social status, caregiving frequency, difficulty sleeping, and bodily pain which were only available at baseline) listed in the table.
d
Age-adjusted and multivariable-adjusted effect of alternate Mediterranean diet score was also adjusted for energy intake (quintiles).