Next Article in Journal
A Review of Knowledge, Belief and Practice Regarding Osteoporosis among Adolescents and Young Adults
Next Article in Special Issue
Shedding Light on the Shade: How Nurseries Protect Their Children from Ultraviolet Radiation
Previous Article in Journal
Detailed Assessment of the Spatial Distribution of Urban Parks According to Day and Travel Mode Based on Web Mapping API: A Case Study of Main Parks in Wuhan
Previous Article in Special Issue
UV Monitoring for Public Health
Article Menu
Issue 8 (August) cover image

Export Article

Open AccessCommunication
Int. J. Environ. Res. Public Health 2018, 15(8), 1726; https://doi.org/10.3390/ijerph15081726

On the Nature of Evidence and ‘Proving’ Causality: Smoking and Lung Cancer vs. Sun Exposure, Vitamin D and Multiple Sclerosis

1
National Centre for Epidemiology and Population Health, Research School of Population Health, The Australian National University, Canberra 2600, Australia
2
Centre for Ophthalmology and Visual Science, University of Western Australia, Perth 6009, Australia
*
Author to whom correspondence should be addressed.
Received: 20 July 2018 / Revised: 20 July 2018 / Accepted: 7 August 2018 / Published: 12 August 2018
(This article belongs to the Special Issue UV Radiation and Health)
Full-Text   |   PDF [2327 KB, uploaded 12 August 2018]   |  

Abstract

If environmental exposures are shown to cause an adverse health outcome, reducing exposure should reduce the disease risk. Links between exposures and outcomes are typically based on ‘associations’ derived from observational studies, and causality may not be clear. Randomized controlled trials to ‘prove’ causality are often not feasible or ethical. Here the history of evidence that tobacco smoking causes lung cancer—from observational studies—is compared to that of low sun exposure and/or low vitamin D status as causal risk factors for the autoimmune disease, multiple sclerosis (MS). Evidence derives from in vitro and animal studies, as well as ecological, case-control and cohort studies, in order of increasing strength. For smoking and lung cancer, the associations are strong, consistent, and biologically plausible—the evidence is coherent or ‘in harmony’. For low sun exposure/vitamin D as risk factors for MS, the evidence is weaker, with smaller effect sizes, but coherent across a range of sources of evidence, and biologically plausible. The association is less direct—smoking is directly toxic and carcinogenic to the lung, but sun exposure/vitamin D modulate the immune system, which in turn may reduce the risk of immune attack on self-proteins in the central nervous system. Opinion about whether there is sufficient evidence to conclude that low sun exposure/vitamin D increase the risk of multiple sclerosis, is divided. General public health advice to receive sufficient sun exposure to avoid vitamin D deficiency (<50 nmol/L) should also ensure any benefits for multiple sclerosis, but must be tempered against the risk of skin cancers. View Full-Text
Keywords: epidemiology; causality; association; smoking; lung cancer; vitamin D; sun exposure; multiple sclerosis epidemiology; causality; association; smoking; lung cancer; vitamin D; sun exposure; multiple sclerosis
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
SciFeed

Share & Cite This Article

MDPI and ACS Style

Lucas, R.M.; Rodney Harris, R.M. On the Nature of Evidence and ‘Proving’ Causality: Smoking and Lung Cancer vs. Sun Exposure, Vitamin D and Multiple Sclerosis. Int. J. Environ. Res. Public Health 2018, 15, 1726.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Int. J. Environ. Res. Public Health EISSN 1660-4601 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top