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Cause specific mortality, social position, and obesity among women who had never smoked: 28 year cohort study

BMJ 2011; 342 doi: http://dx.doi.org/10.1136/bmj.d3785 (Published 28 June 2011) Cite this as: BMJ 2011;342:d3785
  1. Carole L Hart, reader1,
  2. Laurence Gruer, director of public health science2,
  3. Graham C M Watt, professor of general practice3
  1. 1Institute of Health and Wellbeing, Public Health, University of Glasgow, Glasgow G12 8RZ, UK
  2. 2NHS Health Scotland, Glasgow, UK
  3. 3Institute of Health and Wellbeing, General Practice and Primary Care, University of Glasgow, Glasgow, UK
  1. Correspondence to: C L Hart carole.hart{at}glasgow.ac.uk
  • Accepted 6 May 2011

Abstract

Objective To investigate the relations between causes of death, social position, and obesity in women who had never smoked.

Design Prospective cohort study.

Setting Renfrew and Paisley, Scotland.

Participants 8353 women and 7049 men aged 45-64 were recruited to the Renfrew and Paisley Study in 1972-6. Of these, 3613 women had never smoked and were the focus of this study. They were categorised by occupational class (I and II, III non-manual, III manual, and IV and V) and body mass index groups (normal weight, overweight, moderately obese, and severely obese).

Main outcome measures All cause and cause specific mortality during 28 years of follow-up by occupational class and body mass index, using Cox proportional hazards models adjusted for age and other confounders.

Results The women in lower occupational classes who had never smoked were on average shorter and had poorer lung function and higher systolic blood pressure than women in the higher occupational classes. Overall, 43% (n=1555) were overweight, 14% (n=515) moderately obese, and 5% (n=194) severely obese. Obesity rates were higher in lower occupational classes and much higher in all occupational classes than in current smokers in the full cohort. Half the women died, 51% (n=916) from cardiovascular disease and 27% (n=487) from cancer. Relative to occupational class I and II, all cause mortality rates were more than a third higher in occupational classes III manual (relative rate 1.35, 95% confidence interval 1.16 to 1.57) and IV and V (1.34, 1.17 to 1.55) and largely explained by differences in obesity, systolic blood pressure, and lung function. Similar upward gradients were seen for cardiovascular disease and respiratory disease but not for cancer. Mortality rates were highest in severely obese women in the lowest occupational classes.

Conclusions Women who had never smoked and were not obese had the lowest mortality rates, regardless of their social position. Where obesity is socially patterned as in this cohort, it may contribute to health inequalities and increase pressure on health and social services serving more disadvantaged populations.

Footnotes

  • Victor Hawthorne carried out the original Midspan studies. Pauline MacKinnon is the Midspan administrator.

  • Contributors: CLH had full access to the data in the study and can take responsibility for the integrity of the data and the accuracy of the data analysis. The other authors had full access to all the results. All authors contributed to the design of the study. CLH analysed the data and wrote the first draft of the manuscript. All authors contributed to the redrafting of the manuscript and approved the final version. CLH is the guarantor.

  • Funding: This research was supported by NHS Health Scotland. CLH and LG were funded by NHS Health Scotland and GCMW by the University of Glasgow. They had no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; and in the decision to submit the article for publication. The researchers were independent of the funders. All decisions relating to the study were made by the authors alone. The views expressed in the paper may not reflect those of the funding organisations.

  • Competing interests: All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: Not required at the time of the studies.

  • Data sharing: No additional data available.

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