Evidence of a causal relationship between body mass index and psoriasis: A mendelian randomization study
PLOS x January 31, 2019 https://doi.org/10.1371/journal.pmed.1002739
Ashley Budu-Aggrey , Ben Brumpton , Jess Tyrrell , Sarah Watkins , Ellen H. Modalsli, Carlos Celis-Morales, Lyn D. Ferguson, Gunnhild Åberge Vie, Tom Palmer, Lars G. Fritsche, Mari Løset, Jonas Bille Nielsen, Wei Zhou, [ ... ], Lavinia Paternoster [ view all ]
It is amazing that the word vitamin does not occur once in the study
- Multiple Sclerosis increases risk of Psoriasis by 1.9X (both associated with low vitamin D) – meta-analysis Oct 2018
- Psoriasis severity associated with low vitamin D (10 studies) – meta-analysis Jan 2018
Overview Obesity and Vitamin D contains the following summary
- FACT: People who are obese have less vitamin D in their blood
- FACT: Obese need a higher dose of vitamin D to get to the same level of vit D
- FACT: When obese people lose weight the vitamin D level in their blood increases
- FACT: Adding Calcium, perhaps in the form of fortified milk, often reduces weight
- FACT: 126 trials for vitamin D intervention of obesity as of Dec 2017
- FACT: Less weight gain by senior women with > 30 ng of vitamin D
- FACT: Dieters lost additional 5 lbs if vitamin D supplementation got them above 32 ng - RCT
- FACT: Those with darker skins were more likely to be obese Sept 2014
- SUGGESTION: Probably need more than 4,000 IU to lose weight if very low on vitamin D due to
risk factors such as overweight, age, dark skin, live far from equator,shut-in, etc.
- Obesity category has
- Normal weight Obese (50 ng = 125 nanomole)
Diseases which are related due to vitamin D deficiency has the following
- Obesity ==> Diabetes
- Obesity <==> Multiple Sclerosis
- Obesity ==> Cognitive Decline
- Obesity ==> Cancer
- Obesity ==> Migraine Headache
- Psoriasis ==> Metabolic Syndrome on the web
- Psoriasis ==> Metabolic Syndrome
- Psoriasis ==> Kidney Disease
- Psoriasis ==> Heart problems
- Psoriasis ==> Diabetes
Psoriasis is a common inflammatory skin disease that has been reported to be associated with obesity. We aimed to investigate a possible causal relationship between body mass index (BMI) and psoriasis.
Methods and findings
Following a review of published epidemiological evidence of the association between obesity and psoriasis, mendelian randomization (MR) was used to test for a causal relationship with BMI. We used a genetic instrument comprising 97 single-nucleotide polymorphisms (SNPs) associated with BMI as a proxy for BMI (expected to be much less confounded than measured BMI). One-sample MR was conducted using individual-level data (396,495 individuals) from the UK Biobank and the Nord-Trøndelag Health Study (HUNT), Norway. Two-sample MR was performed with summary-level data (356,926 individuals) from published BMI and psoriasis genome-wide association studies (GWASs). The one-sample and two-sample MR estimates were meta-analysed using a fixed-effect model. To test for a potential reverse causal effect, MR analysis with genetic instruments comprising variants from recent genome-wide analyses for psoriasis were used to test whether genetic risk for this skin disease has a causal effect on BMI.
Published observational data showed an association of higher BMI with psoriasis. A mean difference in BMI of 1.26 kg/m2 (95% CI 1.02–1.51) between psoriasis cases and controls was observed in adults, while a 1.55 kg/m2 mean difference (95% CI 1.13–1.98) was observed in children. The observational association was confirmed in UK Biobank and HUNT data sets. Overall, a 1 kg/m2 increase in BMI was associated with 4% higher odds of psoriasis (meta-analysis odds ratio [OR] = 1.04; 95% CI 1.03–1.04; P = 1.73 × 10−60). MR analyses provided evidence that higher BMI causally increases the odds of psoriasis (by 9% per 1 unit increase in BMI; OR = 1.09 (1.06–1.12) per 1 kg/m2; P = 4.67 × 10−9). In contrast, MR estimates gave little support to a possible causal effect of psoriasis genetic risk on BMI (0.004 kg/m2 change in BMI per doubling odds of psoriasis (−0.003 to 0.011). Limitations of our study include possible misreporting of psoriasis by patients, as well as potential misdiagnosis by clinicians. In addition, there is also limited ethnic variation in the cohorts studied.
Our study, using genetic variants as instrumental variables for BMI, provides evidence that higher BMI leads to a higher risk of psoriasis. This supports the prioritization of therapies and lifestyle interventions aimed at controlling weight for the prevention or treatment of this common skin disease. Mechanistic studies are required to improve understanding of this relationship.