Our results showed that 1.37% of the dementia
patients and 0.25% of the control subjects had
been previously diagnosed with bipolar disorder.
Previous studies conducted in Taiwan, including
one from a 1985 community survey – the Taiwan
Psychiatric Epidemiological Project (20) – and
another from the 2000 National Health Insurance
study (21), both estimated prevalence rates for
bipolar affective disorders to be 0.16–0.17%, which
is comparable to the observed prevalence rate in
this study. Of note, the estimated prevalence rate
(0.25%) was representative of the proportion of
treated bipolar patients among the National
Health Insurance (NHI) enrollees in Taiwan. As
such, it might not be comparable to the lifetime
prevalence rate of bipolar disorder in the general
population.
In addition, in the absence of a consensual defi-
nition for prodromal period, we defined
six months as the prodromal interval between
bipolar disorder and dementia in the present study.
To test the robustness of our findings, we further
repeated logistic regression analyses for four different
prodromal intervals: one year, two years, three
years, and five years, separately. Notably, the
results presented in Supplementary Table 1 are
remarkably consistent across the five different prodromal
intervals: six months, one year, two years,
three years, and five years, separately.