Study Finds Sun Exposure Extends Lifespan?

[Dean Pomerleau]

Here is a new study [1] (popular press article) that caught my attention. After following nearly 30,000 Swedish women for 20 years, the researchers found those with the highest intentional sun exposure lived 0.6 - 2.1 years longer on average. While the rate of skin cancer in the high exposure group was higher, they died less from CVD and non-cancer / non-CVD causes during the study, which more than made up for the extra few deaths from skin cancer. The authors suggest it may be the health benefits of higher vitamin D or melatonin that is responsible for the reduced mortality in sun-lovers.

 

I'm not going to go into great depth on this one, because I think the study is pretty flawed. First, Sweden is a very northerly country with an average latitude of 62°. That is equivalently far north as Anchorage Alaska. So people are probably more likely to be vitamin D deficient living that far north, and even a high amount of sun exposure at such northerly latitudes is unlikely to have the same effects (either good or bad) as sun exposure at more southerly points on the globe where most of the world live.

 

 But I think the biggest problem is the vast difference in other demographic and behavioral characteristics between those who got a lot of sun exposure and those who didn't. At study entry, compared to those who avoided the sun, those that got a lot of sun were: younger, less obese/overweight, more physically active, wealthier, less likely to suffer from a comorbidity, better educated, smoked more, and drank more alcohol.  Of course they tried to statistically factor these differences out. But with so many differences between sun-avoiders and sun-worshippers, it's really difficult to determine cause and effect. In other words, is sun exposure really causing increased longevity, or simply a markers for a healthier lifestyle, or better health in general? The authors acknowledge this serious shortcoming in the discussion section:

 

We acknowledge several major limitations of this study. First, it is not possible to differentiate between active sun exposure habits and a healthy lifestyle, and secondly, the results are of an observational nature; therefore, a causal link cannot be proven.

 

So the takeaway is their might be benefits to sun exposure - at least for people living in northern climates. But I'd definitely continue to use sunscreen, particularly if you live more south than Sweden.

 

--Dean

 

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[1] J Intern Med. 2016 Mar 16. doi: 10.1111/joim.12496. [Epub ahead of print]

 

Avoidance of sun exposure as a risk factor for major causes of death: a competing

risk analysis of the Melanoma in Southern Sweden cohort.

 

Lindqvist PG(1), Epstein E(2), Nielsen K(3), Landin-Olsson M(4), Ingvar C(5),

Olsson H(6).

 

Free Full text: http://onlinelibrary.wiley.com/doi/10.1111/joim.12496/epdf

 

OBJECTIVE: Women with active sunlight exposure habits experience a lower

mortality rate than women who avoid sun exposure; however, they are at an

increased risk of skin cancer. We aimed to explore the differences in main causes

of death according to sun exposure.

 

METHODS: We assessed the differences in sun exposure as a risk factor for

all-cause mortality in a competing risk scenario for 29 518 Swedish women in a

prospective 20-year follow-up of the Melanoma in Southern Sweden (MISS) cohort.

Women were recruited from 1990 to 1992 (aged 25-64 years at the start of the

study). We obtained detailed information at baseline on sun exposure habits and

potential confounders. The data were analysed using modern survival statistics.

RESULTS: Women with active sun exposure habits were mainly at a lower risk of

cardiovascular disease (CVD) and noncancer/non-CVD death as compared to those who

avoided sun exposure. As a result of their increased survival, the relative

contribution of cancer death increased in these women. Nonsmokers who avoided sun

exposure had a life expectancy similar to smokers in the highest sun exposure

group, indicating that avoidance of sun exposure is a risk factor for death of a 

similar magnitude as smoking. Compared to the highest sun exposure group, life

expectancy of avoiders of sun exposure was reduced by 0.6-2.1 years.

CONCLUSION: The longer life expectancy amongst women with active sun exposure

habits was related to a decrease in CVD and noncancer/non-CVD mortality, causing 

the relative contribution of death due to cancer to increase.

 

PMID: 26992108

[AlPater]

A kind off-list correspondent alerted me to the below EurekaAlert article re
an article which I had found previously and had "in press" to report.  The
correspondent said he would post to the CR Forum were it not for flak he
might get from others.  I wish I could persuade him to post the message
since I feel that he has much to contribute.

Since the most recent paper seemed to not address the vitamin D/elephant in
the room issue, I dug up some earlier information in earlier literature.

I do derive much satisfaction of walking in sunshine with little
"protection", but not to the point of sunburn, irrespective of health
benefits, so I think it benefits my psyche too.


http://www.eurekalert.org/pub_releases/2016-03/w-wds032216.php

22-MAR-2016
Why do sunbathers live longer than those who avoid the sun?

New research looks into the paradox that women who sunbathe are likely to
live longer than those who avoid the sun, even though sunbathers are at an
increased risk of developing skin cancer.

An analysis of information on 29,518 Swedish women who were followed for 20
years revealed that longer life expectancy among women with active sun
exposure habits was related to a decrease in heart disease and
noncancer/non-heart disease deaths, causing the relative contribution of
death due to cancer to increase.

Whether the positive effect of sun exposure demonstrated in this
observational study is mediated by vitamin D, another mechanism related to
UV radiation, or by unmeasured bias cannot be determined. Therefore,
additional research is warranted.

"We found smokers in the highest sun exposure group were at a similar risk
as non-smokers avoiding sun exposure, indicating avoidance of sun exposure
to be a risk factor of the same magnitude as smoking," said Dr. Pelle
Lindqvist, lead author of the Journal of Internal Medicine study.
"Guidelines being too restrictive regarding sun exposure may do more harm
than good for health."

Avoidance of sun exposure as a risk factor for major causes of death: a
competing risk analysis of the Melanoma in Southern Sweden cohort.
Lindqvist PG, Epstein E, Nielsen K, Landin-Olsson M, Ingvar C, Olsson H.
J Intern Med. 2016 Mar 16. doi: 10.1111/joim.12496. [Epub ahead of print]
PMID: 26992108
http://onlinelibrary.wiley.com/doi/10.1111/joim.12496/full
http://onlinelibrary.wiley.com/doi/10.1111/joim.12496/epdf
http://onlinelibrary.wiley.com/doi/10.1111/joim.12496/pdf

Abstract

OBJECTIVE:

Women with active sunlight exposure habits experience a lower mortality rate
than women who avoid sun exposure; however, they are at an increased risk of
skin cancer. We aimed to explore the differences in main causes of death
according to sun exposure.

METHODS:

We assessed the differences in sun exposure as a risk factor for all-cause
mortality in a competing risk scenario for 29 518 Swedish women in a
prospective 20-year follow-up of the Melanoma in Southern Sweden (MISS)
cohort. Women were recruited from 1990 to 1992 (aged 25-64 years at the
start of the study). We obtained detailed information at baseline on sun
exposure habits and potential confounders. The data were analysed using
modern survival statistics.

RESULTS:

Women with active sun exposure habits were mainly at a lower risk of
cardiovascular disease (CVD) and noncancer/non-CVD death as compared to
those who avoided sun exposure. As a result of their increased survival, the
relative contribution of cancer death increased in these women. Nonsmokers
who avoided sun exposure had a life expectancy similar to smokers in the
highest sun exposure group, indicating that avoidance of sun exposure is a
risk factor for death of a similar magnitude as smoking. Compared to the
highest sun exposure group, life expectancy of avoiders of sun exposure was
reduced by 0.6-2.1 years.

CONCLUSION:

The longer life expectancy amongst women with active sun exposure habits was
related to a decrease in CVD and noncancer/non-CVD mortality, causing the
relative contribution of death due to cancer to increase.

KEYWORDS:

CVD ; cigarette smoke; cohort study; melanoma; mortality; public health


Sunlight Has Cardiovascular Benefits Independently of Vitamin D.
Weller RB.
Blood Purif. 2016;41(1-3):130-4. doi: 10.1159/000441266. Epub 2016 Jan 15.
PMID: 26766556 Free Article
http://www.karger.com/Article/FullText/441266
http://www.karger.com/Article/Pdf/441266

Abstract

BACKGROUND:

High blood pressure (BP) is the leading risk factor for disability adjusted
life years lost globally. Epidemiological data show a correlation between
increased sun exposure and reduced population BP and cardiovascular
mortality. Individuals with high serum vitamin D levels are at reduced risk
of hypertension, cardiovascular disease and metabolic syndrome, yet multiple
trial data show that oral vitamin D supplementation has no effect on these
endpoints. Sunlight is a risk factor for skin cancers, but no link has been
shown with increased all-cause mortality. Cohort studies from Scandinavia
show a dose-dependent fall in mortality with increased sun-seeking
behaviour. Skin contains significant stores of nitrogen oxides, which can be
converted to NO by UV radiation and exported to the systemic circulation.
Human studies show that this pathway can cause arterial vasodilatation and
reduced BP. Murine studies suggest the same mechanism may reduce metabolic
syndrome.

SUMMARY:

Sunlight has beneficial effects on cardiovascular risk factors independently
of vitamin D.

KEY MESSAGES:

All-cause mortality should be the primary determinant of public health
messages. Sunlight is a risk factor for skin cancer, but sun avoidance may
carry more of a cost than benefit for overall good health.


Ultraviolet exposure and mortality among women in Sweden.
Yang L, Lof M, Veierød MB, Sandin S, Adami HO, Weiderpass E.
Cancer Epidemiol Biomarkers Prev. 2011 Apr;20(4):683-90. doi:
10.1158/1055-9965.EPI-10-0982. Epub 2011 Feb 4. Erratum in: Cancer Epidemiol
Biomarkers Prev. 2011 Jun;20(6):1259.
PMID: 21297041 Free Article
http://cebp.aacrjournals.org/content/20/4/683.long
http://cebp.aacrjournals.org/content/20/4/683.full.pdf+html
http://cebp.aacrjournals.org/content/20/4/683/T3.expansion.html

Abstract

BACKGROUND:

Ecological studies have reported possible effects of sunlight on the risk of
several diseases. Little evidence is available on the association between
mortality and solar and artificial UV exposure by individual level from
prospective studies.

METHODS:

The Swedish Women's Lifestyle and Health cohort study included women aged 30
to 49 years in 1991-1992. Participants completed a questionnaire and were
followed-up through linkages to national registries until the end of 2006.
Cox models were used to estimate adjusted HRs and 95% CIs for all-cause
mortality and for cancer and cardiovascular disease (CVD) mortality.

RESULTS:

During 15 years of follow-up, among the 38,472 women included in the present
study, 754 deaths occurred: 457 due to cancer and 100 due to CVD. When
combining the information on sun exposure from age 10 to 39 years, women who
got sunburned twice or more per year during adolescence had a reduced
all-cause mortality, compared with women who had been sunburned once or
less. A reduced risk for all-cause and CVD mortality was observed in women
who went on sunbathing vacations more than once a year over three decades.
Solarium use once or more per month for at least one decade increased the
risk of all-cause mortality, when compared with women who never used a
solarium.

CONCLUSIONS:

Solar UV exposure was associated with reduced overall and CVD mortality,
whereas artificial UV exposure was associated with increased overall and
cancer mortality among Swedish women.

IMPACT:

Moderate sun exposure may protect against cause-specific mortality.


Can UV exposure reduce mortality?
Berwick M.
Cancer Epidemiol Biomarkers Prev. 2011 Apr;20(4):582-4. doi:
10.1158/1055-9965.EPI-10-1255.
PMID: 21454422 Free Article
http://cebp.aacrjournals.org/content/20/4/582.long

Abstract

A Swedish cohort analysis in this issue (1) demonstrates a significant
reduction in all cause mortality and in cardiovascular mortality associated
with several measures of sun exposure. In addition, ultraviolet exposure
from tanning beds is associated with a significant increase in all cause
mortality and cancer mortality. A potential explanation for the protective
association is that UV exposure results in high levels of serum vitamin D
which may improve survival. However, that explanation does not hold for
ultraviolet exposure from tanning beds, which in this study is associated
with a significant increase in all cause mortality and cancer mortality.
Such a finding is curious and inconsistent with a vitamin D hypothesis.
These results should impel investigators to study further the biology of
ultraviolet radiation, both natural and artificial, and its health effects.

[Sthira]

I spend a lot of time in the sun particularly in spring, summer and fall. Winter I hibernate.

 

For sunscreen, I use this from Skin Actives: http://www.skinactives.com/Sunscreen-SPF-30-Advanced-Protection.html

 

I'm not sure this particular sunscreen is any better than anything else, but I like Dr. Sivak and like her small honest company: http://www.skinactives.com/blog/?cat=8