Associations between parenthood and dementia in men and women: biology or confounding?

BMC Neurology

Table 1 Characteristics at the start of follow-up^a for a cohort of persons ≥ 40 years old followed in the period 1994–2017 in Denmark

Characteristic at the start of follow-up	Women (n = 2 222 638)		Men (n = 2 141 002)
Characteristic at the start of follow-up	Number^b	%	Number^b	%
Number of children
0	564 573	25.40	592 939	27.69
1	401 421	18.06	373 570	17.45
2	783 069	35.23	726 956	33.95
3	347 885	15.65	325 197	15.19
4	92 119	4.14	89 209	4.17
≥ 5	33 571	1.51	33 131	1.55
Age (years) at birth of first child
No children	555 211	24.98	561 562	26.23
< 20	179 332	8.07	41 620	1.94
20–24	606 326	27.28	384 139	17.94
25–29	523 463	23.55	582 783	27.22
30–34	245 374	11.04	357 208	16.68
35–39	91 564	4.12	148 242	6.92
≥ 40	21 368	0.96	65 448	3.06
Year of birth
< 1920	247 881	11.15	146 530	6.84
1920–1929	243 485	10.95	207 143	9.68
1930–1939	267 286	12.03	261 136	12.20
1940–1949	379 109	17.06	394 804	18.44
1950–1959	378 924	17.05	397 864	18.58
1960–1969	416 376	18.73	438 513	20.48
≥ 1970	289 577	13.03	295 012	13.78
Age (years) at the start of follow-up
< 45	1 121 354	50.45	1 169 290	54.61
45–49	206 725	9.30	216 958	10.13
50–54	163 816	7.37	168 910	7.89
55–59	138 038	6.21	136 313	6.37
60–64	124 592	5.61	117 222	5.48
65–69	122 810	5.53	1081 96	5.05
≥ 70	345 303	15.54	224 113	10.47
Heart disease
Yes	21 543	0.97	22 857	1.07
No	2 201 095	99.03	2 118 145	98.93
Stroke
Yes	54 314	2.44	78 281	3.66
No	2 168 324	97.56	2 062 721	96.34
Kidney disease
Yes	2323	0.10	2976	0.14
No	2 220 315	99.90	2 138 026	99.86
Diabetes
Yes	35 229	1.59	38 608	1.80
No	2 187 409	98.41	2 102 394	98.20
Hypertension
Yes	69 887	3.14	42 142	1.97
No	2 152 751	96.86	2 098 860	98.03

^aFollow-up began on 1 January 1994 or at 40 years of age, whichever came later. Accordingly, persons who began follow-up in 1994 represented a range of ages from 40 to 109 years. In contrast, persons who began follow-up at a later date were necessarily all 40 years of age at study entry, as they had aged into the cohort. This condition accounts for the overrepresentation of persons < 45 years of age at the start of follow-up
^bNote that these totals reflect the numbers at the start of follow-up. Because relatively young persons were overrepresented at this point, rates of heart disease, stroke, kidney disease, diabetes, and hypertension are lower than might be expected if the age distribution of the cohort at the start of follow-up reflected the age distribution in the general population. Since with the exception of birth year, age at birth of the first child, and age at the start of follow-up, all variables were time-dependent, variable distributions will have changed during the study period

ISSN: 1471-2377