TABLE 1.
Characteristics of the total sample and subsamples BD‐I disorder versus BD‐II disorder
| Total sample (max N = 963) | BD‐I (max N = 714, 74.1%) | BD‐II (max N = 249, 25.9%) | p‐value (Mann–Whitney U/Fisher exact) | Controlled for study cohort a t‐value, p‐value | |
|---|---|---|---|---|---|
| Sociodemographic variables | |||||
| Age (in years) | N = 963 | N = 714 | N = 249 | 0.048* | 1.069, 0.285 |
| M (SD) | 63.1 (8.8) | 62.8 (8.7) | 64.1 (8.9) | ||
| Gender | N = 963 | N = 714 | N = 249 | 1.000 | 0.148, 0.882 |
| Female | 56.1% (540) | 56.0% (400) | 56.2% (140) | ||
| Male | 43.9% (423) | 44.0% (314) | 43.8% (109) | ||
| Education level (in years of education) | N = 767 | N = 572 | N = 195 | 0.969 | 0.919, 0.359 |
| M (SD) | 13.1 (3.8) | 13.1 (3.8) | 13.1 (4.0) | ||
| Employment status | N = 634 | N = 460 | N = 174 | 0.214 | −0.707, 0.480 |
| Working | 24.3% (154) | 25.7% (118) | 20.7% (36) | ||
| Not working | 75.7% (480) | 74.3% (342) | 79.3% (138) | ||
| Relationship status | N = 799 | N = 595 | N = 204 | 0.359 | 0.082, 0.935 |
| Currently single | 58.4% (467) | 59.7% (355) | 54.9% (112) | ||
| In steady relationship | 41.6% (332) | 40.3% (240) | 45.1% (92) | ||
| Clinical variables | |||||
| Age of onset (in years) | N = 767 | N = 569 | N = 198 | 0.256 | 1.113, 0.266 |
| M (SD) | 31.7 (15.0) | 31.3 (14.8) | 33.2 (15.8) | ||
| Late onset (first episode ≥50 years) | N = 767 | N = 569 | N = 198 | 0.013* | 2.645, 0.008** |
| Yes | 14.2% (109) | 12.3% (70) | 19.7% (39) | ||
| No | 85.8% (658) | 87.7% (499) | 80.3% (159) | ||
| Duration since start illness or BD diagnosis (in years) | N = 874 | N = 656 | N = 218 | 0.491 | −1.190, 0.235 |
| M (SD) | 32.0 (13.7) | 32.2 (13.6) | 31.2 (14.0) | ||
| Number of affective episodes (lifetime) | N = 678 | N = 500 | N = 178 | 0.045* | 1.068, 0.286 |
| M (SD) | 20.0 (44.3) | 19.5 (47.7) | 21.3 (32.8) | ||
| Depression severity b | N = 841 | N = 634 | N = 207 | 0.007** |
Mild vs. no: −0.247, 0.805 Severe vs. no: 1.946, 0.052 Mild vs. severe: −2.045, 0.041* |
| No depression | 58.9% (495) | 59.0% (374) | 58.5% (121) | ||
| Mild to moderate depression | 36.9% (310) | 38.0% (241) | 33.3% (69) | ||
| Severe depression | 4.3% (36) | 3.0% (19) | 8.2% (17) | ||
| Manic symptoms (YMRS) | N = 881 | N = 665 | N = 216 | 0.773 | −0.582, 0.560 |
| M (SD) | 4.0 (5.4) | 4.0 (5.5) | 3.9 (5.0) | ||
| Rapid cycling (lifetime) | N = 426 | N = 309 | N = 117 | 0.093 | 1.526, 0.128 |
| No history of rapid cycling | 85.2% (363) | 87.1% (269) | 80.3% (94) | ||
| Possible/probable/definite history of rapid cycling | 14.8% (63) | 12.9% (40) | 19.7% (23) | ||
| Ever hospitalized for psychiatric condition | N = 613 | N = 448 | N = 165 | <0.001*** | −6.088, <0.001*** |
| Yes | 74.6% (457) | 80.8% (362) | 57.6% (95) | ||
| No | 25.4% (156) | 19.2% (86) | 42.4% (70) | ||
| Lithium use (current) | N = 909 | N = 675 | N = 234 | 0.488 | −0.775, 0.439 |
| Yes | 40.4% (367) | 39.7% (268) | 42.3% (99) | ||
| No | 59.6% (542) | 60.4% (407) | 57.7% (135) | ||
| Anti‐psychotic use (current) | N = 919 | N = 683 | N = 236 | 0.023* | −2.953, 0.003** |
| Yes | 45.5% (418) | 47.7% (326) | 39.0% (92) | ||
| No | 54.5% (501) | 52.3% (357) | 61.0% (144) | ||
| Smoking | N = 496 | N = 348 | N = 148 | 0.550 |
Lifetime vs. never: 0.201, 0.841 Current vs. never: 0.799, 0.424 Current vs. lifetime: 0.635, 0.526 |
| Never | 31.7% (157) | 33.0% (115) | 28.4% (42) | ||
| Lifetime smoker (past) | 30.6% (152) | 30.5% (106) | 31.1% (46) | ||
| Current smoker | 37.7% (187) | 36.5% (127) | 40.5% (60) | ||
| Outcome variables | |||||
| GAF score | N = 437 | N = 306 | N = 131 | 0.473 | −0.189, 0.851 |
| M (SD) | 61.0 (12.0) | 60.6 (12.1) | 62.0 (11.9) | ||
| Cognitive g‐score c | N = 324 | N = 230 | N = 94 | 0.191 | −0.398, 0.691 |
| M (SD) | 0.05 (0.94) | −0.002 (0.97) | 0.16 (0.85) | ||
| Somatic burden d | N = 513 | N = 413 | N = 100 | 0.831 | −0.083, 0.934 |
| M (SD) | 2.47 (2.1) | 2.47 (2.1) | 2.45 (2.1) | ||
Abbreviations: BD, Bipolar Disorder; BD‐I, bipolar I disorder; BD‐II, bipolar II disorder; CES‐D, Center for Epidemiologic Studies Depression Scale; GAF, Global Assessment of Functioning; HAMD, Hamilton Depression Rating Scale; M, mean; MDRS, Montgomery–Asberg Depression Rating Scale; SD, standard deviation; YMRS, Young Mania Rating Scale.
Note: *p < 0.05 **p < 0.01 ***p < 0.001.
Generalized linear mixed model (GLMM) using a binomial probability distribution with a logit link function and random effect of study cohort with outcome BD subtype.
The depression severity band was harmonized from MDRS, HAMD, and CES‐D, see text for cut‐offs.
Cognitive g‐score: a continuous z‐score scaling metric with mean = 0, SD = 1, range − 1.00 to +1.00, see text for procedure.
Somatic burden: total number of somatic diseases, out of eight disease categories. Only calculated for participants with available data for all of the eight disease categories (N = 513).