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Association between mid-life marital status and cognitive function in later life: population based cohort study

BMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b2462 (Published 02 July 2009) Cite this as: BMJ 2009;339:b2462

Re: Marital status and the risk of dementia

We were interested to read about these results based on a Chinese
population, which confirms our main finding, that married people had a
lower risk of dementia compared to non-married or non-cohabitant persons.
Concerning the non-married subgroups, there are however some interesting
differences between results, mainly that singles had a higher risk than in
our population. We think that these differences may be related to both
methodological and cultural differences between the studies. In the study
by Chen et al, as reported in the comment, participants were already at
baseline >65 years old, whereas our participants were relatively young,
averagely 50.4 years.(1) In the most recent article referred to by Chen
from 2008, the follow-up time for the Chinese sample seems to have been
only one year,(2) although, as stated in the comment, the measurements
were performed over a 5-7 year period. In our case the follow-up was
averagely 21 years. The diagnosis we used was according to the Diagnostic
and Statistical Manual of Mental Disorders, 4th edition (DSM-IV), combined
with magnetic resonance imaging, whereas Chen et al used the Automated
Geriatric Examination for Computer Assisted Taxonomy (AGECAT) to classify
participants as cognitively impaired or healthy. Similar adjustments were
made in both studies with the important exception that we also adjusted
for carrying the apolipoprotein 4 allele (ApoE e4). We think it is
important to have these differences in mind when comparing results.

Chen reports, in comparison to our results, a lower and a
statistically insignificant odds ratio for divorced and widowed (1.22,
with a confidence interval of 0.67 to 2.25) and a higher odds ratio for
singles (5.32, 1.14 to 24.8). If widowed and divorced at both midlife and
late-life are combined in our study, as in the comment by Chen, the odds
ratio amounts to a much higher 3.35 (1.8 to 6.1) - compared to cohabitants
at both occasions. From the information we could obtain from a previous
article,(3) we estimate that the participants in Chen’s study were
averagely between 72-73 years old at baseline. For that reason, and also
due to the very short follow-up time in their study, it might however be
more appropriate to compare with the marital status data we have from the
follow-up data in our study, rather than from midlife data. (Our
participants were averagely 71 years at follow-up.) As we also have data
from midlife, we can specifically calculate the odds ratio for those who
were cohabitants at midlife but who either were widowed or divorced after
midlife. The odds ratio for this group is a non-significant 1.57 (0.9 to
2.6), and thus not very different from the results that Chen reports in
his comment. A possible interpretation of this difference is that losing a
partner relatively early in life may be a more traumatic and health
threatening event than when this occurs in later life, at least on a group
level.

As for the singles, this category is defined by Chen in the same way
as we have, i.e. as never-married. We notice the high confidence interval
in the results reported in the comment, but an odds ratio of 5.23 (1.14 to
24.8) still indicates that the risk increase of single-hood for dementia
may be higher in China than we and others have found for a European
population.(1, 4) This difference is interesting in speculating about the
under-lying factors behind the association between marital status and
dementia. We can only speculate about this, but perhaps the relatively low
risk increase for singles in Europe is related to a difference in social
status and integration in society of singles between cultures. It has been
reported that singles in the US have a considerably lower social status
than married. (5) In China, due to gender imbalance, single-hood also may
have other social implications than in Europe, implications that may also
be related to dementia risk. In conclusion, we think that cultural
differences most probably exist in the way members of different groups of
marital status are perceived and treated. If such differences can be
related to differences in the association between marital status and
dementia in different cultures, such data could be of potential value to
help identifying mechanisms behind the disease.

1. Hakansson K, Rovio S, Helkala E-L, Vilska A-R, Winblad B, Soininen
H, Nissinen A, Mohammed AH, Kivipelto M. Association between mid-life
marital status and cognitive function in later life: population based
cohort study. BMJ. 2009;339(jul02_2):b2462-.

2. Chen RL, Hu Z, Wei L, Qin X, McCracken C, Copeland JR. Severity of
depression and risk for subsequent dementia: cohort studies in China and
the UK. Br J Psychiatry. 2008;193(5):373-377.

3. Chen RL, Hu Z, Qin X, Xu XC, Copeland JRM. A community-based study
of depression in older people in Hefei, China - the GMS-AGECAT prevalence,
case validation and socio-economic correlates. Int J Geriatr Psychiatr.
2004;19(5):407-413.

4. Helmer C, Damon D, Letenneur L, Fabrigoule C, Barberger-Gateau P,
Lafont S, Fuhrer R, Antonucci T, Commenges D, Orgogozo JM, Dartigues JF.
Marital status and risk of Alzheimer's disease: a French population-based
cohort study. Neurology. 1999;53(9):1953-1958.

5. DePaulo BM, Morris WL. Singles in society and in science. Psychol
Inq. 2005;16(2-3):57-83.

Competing interests:
None declared

Competing interests: No competing interests

07 August 2009
Krister Håkansson
research fellow
Miia Kivipelto
Växjö University, 35195 Växjö and the Karolinska Institutet, 14186 Stockholm, Sweden