Smoking affects everybody, even non-smokers. In fact, it can be argued that non-smokers are greatly affected compared to smokers. Numerous studies have revealed the many dangers of first-hand, second-hand and third-hand smoke. Recently, a team of Japanese researchers found how one's age can literally go up in smoke due to smoking. The mechanism of how smoking accelerates aging has been identified.

A team of researchers from the Osaka University in Japan led by assistant professor Kaori Nakanishi and professor of the Health Care Centre Keiko Takihara found smoking affects the aging-related molecule called alpha-klotho in the blood serum. Relatively, smoking also increased the concentration of metabolism-related fibroblast growth factor (FGF)-21 in the blood serum.

Healthy men aged 40-years-old and above in Japan participated in the study wherein they took numerous health examinations. Levels of growth factors, several cytokines (substances secreted by cells in the immune system that affect other cells), along with other biochemical and physical parameters were acquired from the subjects. Other information such as medical history, current medication, smoking habits, level of psychological stress and sleeping duration were obtained through questionnaires and reconfirmed through interviews by nurses.

"Among middle-aged men, serum levels of FGF-21, soluble alpha-klotho and inflammation-related cytokine interleukin (IL)-6 were significantly higher in smokers than in never-smokers," the researchers wrote. Moreover, levels of the aging-related alpha-Klotho rise during stressful instances such as emotional stress and lack of sleep.

Adiponectin is another cytokine linked to metabolism. Among smokers, FGF-21 has a negative correlation with adiponectin. The researchers believe that the rise of FGF-21 among smokers is a sign of metabolic disorder. Among non-smokers, alpha-Klotho has a positive correlation with IL-6, which smokers don't have.

Previous studies found alpha-Klotho has anti-inflammatory properties. The absence of a positive correlation between IL-6 and alpha-Klotho in smokers could be explained by the weakened anti-inflammatory properties of alpha-Klotho caused by smoking stress.

The scientists hoped to shed light on how smoking accelerates aging at a biochemical level. Findings can be beneficial to other studies looking into aging-related illnesses caused by smoking and smoking-enhanced aging. The Japanese research team published their study in Nature's Scientific Reports journal on Sep. 18.