Background
The relationship between baldness and heart disease is still controversial. We performed an updated meta-analysis of observational studies to evaluate the relation between heart disease and androgenic alopecia or alopecia areata.

Aims
To evaluate the relation between heart disease and androgenic alopecia or alopecia areata.

Methods
Studies were identified by searching Medline and Embase up to October 20, 2017 without language restriction. Meta-analysis was performed by using a random-effects model.

Results
Nine studies were included in the meta-analysis (eight on androgenic alopecia and one on alopecia areata: 44,806 participants).

Compared to men without baldness, men with androgenic alopecia had an increased risk of heart disease (relative risk (RR): 1.32, 95 per cent CI: 1.08 to 1.63, p=0.01, I2=25 per cent), and younger men (< 55 or ≤ 60 years) showed a stronger association (RR: 1.44, 95 per cent CI: 1.11 to 1.86, p=0.01, I2=0 per cent). The positive relation depended on the severity of baldness and decreased in order of severe vertex (RR: 1.60, 95 per cent CI: 1.19 to 2.16, p=0.002), moderate vertex (RR: 1.41, 95 per cent CI: 1.22 to 1.64, p < 0.001), mild vertex (RR: 1.18, 95 per cent CI: 1.05 to 1.33, p=0.007), and frontal baldness (RR: 1.10, 95 per cent CI: 0.92 to 1.32, p=0.28)). In contrast, there was no significant relation between alopecia areata and heart disease (RR: 0.91, 95 per cent CI: 0.60 to 1.39, p=0.66).

Conclusion
Androgenic alopecia is associated with heart disease, but alopecia areata is not.