Exercise and Depression in Midlife:
A Prospective Study
Lisa Cooper-Patrick, MD, MPH, Daniel E. Ford, MD, MPH, Lucy A. Mead,
ScM, Patricia P. Chang, MD, and Michael J. Klag, MD, MPH
Introduction
Measurements
It has been suggested that exercise is
associated with better mental health. '-3
However, interventional studies have many
methodologic problems, including the
nonrandom assignment of participants to
experimental conditions and the inability
to blind participants to a physical activity
intervention.3'4 Prospective observational
studies have produced contradictory re-
sults.57 We hypothesized that (1) physical
activity is protective against depression
and psychiatric distress and (2)
this
protective effect is accentuated in vulner-
able individuals, specifically those with an
"unstable" temperament or with a paren-
tal history of depression.
Methods
Study Population
The Precursors Study is a longitudi-
nal cohort study of 1337 former medical
students from the Johns Hopkins Univer-
sity School of Medicine classes of 1948
through 1964. More than 95% of eligible
students were enrolled.8 The study con-
ducts annual follow-up by mailed ques-
tionnaires, with 5-year response rates
ranging from 87% to 93%.
The first analysis assessed the rela-
tionship between self-reported physical
activity in 1978 and the incidence of
clinical depression through 1993. Partici-
pants who died before 1978 (n = 61), did
not respond to the 1978 questionnaire
(n = 465), reported an episode of depres-
sion in 1978 or earlier (n = 52), or were
lost to follow-up after 1978 (n = 7) were
excluded from this analysis, leaving 752
eligible participants.
The second analysis assessed the
relationship between self-reported physi-
cal
activity
in 1986 and psychiatric
distress by the General Health Question-
naire in 1988. Participants who died
before 1986 (n = 106), did not respond to
the 1986 questionnaire (n = 290), died in
1987 or 1988 (n = 13), did not complete
the questionnaire in 1988 (n = 109), or
were lost to follow-up (n = 38) were
exclude