Low physical activity and mortality in women: baseline lifestyle and health as alternative explanations.
OBJECTIVE
The aim of this study was to investigate the association between physical activity and mortality in post-menopausal women. In addition, the authors wanted to investigate to what extent this association could be attributed to confounding from other lifestyle factors, and to reverse causation due to a number of common health problems that may inhibit the ability to exercise.


METHODS
A total of 27,734 women aged 51-83 years from the Swedish Mammography Cohort were investigated. In 1997 they responded to a detailed questionnaire including questions on physical activity, diet, alcohol intake, smoking, and medical problems. During follow-up in 1999-2004, 1,232 deaths were identified by linkage to the National Population Register.


RESULTS
Women with low physical activity (35 MET*h/day) had a 3.22 times increased mortality (95% confidence interval (CI) = 2.35-4.43) compared with the most active women (>50 MET*h/day). No increased risk was seen in women with moderate compared with high physical activity. Sedentary women tended to have a less healthy lifestyle and more health problems at baseline, e.g. almost 30% of them reported high blood pressure compared with less than 20% of active women. Baseline medical problems and lifestyle factors such as smoking, diet, and education accounted for 30% of the excess risk seen in sedentary women (24% and 6% respectively).


CONCLUSIONS
This study indicates that even fairly small amounts of activity will reduce mortality in older women. However, sedentary women seemed to be a selected group with more medical problems and a less healthy lifestyle. The findings indicate that the association between physical inactivity and mortality will be overestimated if this is not taken into account.
Carlsson
Sofia
S
Division of Epidemiology and Social Medicine, Stockholm Centre for Public Health, Stockholm, Sweden. sofia.carlsson@imm.ki.se
Andersson
Tomas
T
Wolk
Alicja
A
Ahlbom
Anders
A
D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D015986:Confounding Factors, Epidemiologic; D015444:Exercise; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007899:Leisure Activities; D008019:Life Style; D008875:Middle Aged; D009026:Mortality; D017698:Postmenopause; D012307:Risk Factors; D011795:Surveys and Questionnaires; D016387:Women's Health