Objectives To examine whether exposure to heavy physical work from early to later adulthood is associated with primary healthcare visits due to cause-specific musculoskeletal diseases in midlife.

Design Prospective cohort study.

Setting Nationally representative Young Finns Study cohort, Finland.

Participants 1056 participants of the Young Finns Study cohort.

Exposure measure Physical work exposure was surveyed in early (18–24 years old, 1986 or 1989) and later adulthood (2007 and 2011), and it was categorised as: ‘no exposure’, ‘early exposure only’, ‘later exposure only’ and ‘early and later exposure’.

Primary and secondary outcome measures Visits due to any musculoskeletal disease and separately due to spine disorders, and upper extremity disorders were followed up from national primary healthcare register from the date of the third survey in 2011 until 2014.

Results Prevalence of any musculoskeletal disease during the follow-up was 20%, that for spine disorders 10% and that for upper extremity disorders 5%. Those with physically heavy work in early adulthood only had an increased risk of any musculoskeletal disease (risk ratio (RR) 1.55, 95% CI 1.05 to 2.28) after adjustment for age, sex, smoking, body mass index, physical activity and parental occupational class. Later exposure only was associated with visits due to any musculoskeletal disease (RR 1.46, 95% CI 1.01 to 2.12) and spine disorders (RR 2.40, 95% CI 1.41 to 4.06). Early and later exposure was associated with all three outcomes: RR 1.99 (95% CI 1.44 to 2.77) for any musculoskeletal disease, RR 2.43 (95% CI 1.42 to 4.14) for spine disorders and RR 3.97 (95% CI 1.86 to 8.46) for upper extremity disorders.

Conclusions To reduce burden of musculoskeletal diseases, preventive actions to reduce exposure to or mitigate the consequences of physically heavy work throughout the work career are needed.