* Peter S. Millard

Dr. Hall bases his analysis on observational data that are of questionable validity. The fact that churchgoers live longer than people who do not attend church may very well have nothing to do with churchgoing but may result from uncontrolled confounding.

Observational studies that showed a benefit of exogenous estrogens in postmenopausal women were debunked by the Women’s Health Initiative Randomized Controlled Trial.1 The accepted explanation for the discrepancy between the observational findings and the experimental results is that women who took estrogens were systematically different from non-users in ways which resulted in improved outcomes (eg, reduced coronary disease).

Barrett-Connor referred to this as the “healthy user effect.”2 The inability to control for the healthy user effect resulted in the biased findings of many observational studies of estrogen use.

Similarly, churchgoers are systematically different from non-churchgoers in ways that are difficult to measure but are likely to result in improved health outcomes that may have nothing to do with churchgoing. Churchgoers are more likely to be employed, have intact families, and are less likely to be homebound by illness or disability. Until the healthy attender effect can be controlled for, it is unwise to attempt to make any inferences about the effect that churchgoing has on health.

## References

1.  The Women’s Health Initiative Steering Committee. Effects of conjugated equine estrogen in postmenopausal women with hysterectomy: the Women’s Health Initiative Randomized Controlled Trial. JAMA 2004; 291: 1701–12.
    
    [CrossRef](http://www.jabfm.org/lookup/external-ref?access_num=10.1001/jama.291.14.1701&link_type=DOI) 
    
    [PubMed](http://www.jabfm.org/lookup/external-ref?access_num=15082697&link_type=MED&atom=%2Fjabfp%2F19%2F4%2F431.1.atom) 
    
    [Web of Science](http://www.jabfm.org/lookup/external-ref?access_num=000220788700027&link_type=ISI) 

2.  Barrett-Connor E, Bush TL. Estrogen and coronary heart disease in women. JAMA 1991; 265: 1861–7.
    
    [CrossRef](http://www.jabfm.org/lookup/external-ref?access_num=10.1001/jama.1991.03460140089033&link_type=DOI) 
    
    [PubMed](http://www.jabfm.org/lookup/external-ref?access_num=2005736&link_type=MED&atom=%2Fjabfp%2F19%2F4%2F431.1.atom) 
    
    [Web of Science](http://www.jabfm.org/lookup/external-ref?access_num=A1991FE86200029&link_type=ISI)